The Two Simon's Theory

[warksfarmer]

A bit more circumstancial eveidence

2 fields of wheat on a block of land with same rotation for at least 20 years drilled same day same seed, same seed rate and same operator even and treated identically since drilling

solitice following spring oats, straw chopped both had no cultivation

first field drilled with 750a, could find evidence of hair-pining on the day second field drilled with Dale

the Dale field is much thicker and plants are taller, no thin or bare patches

750a field is fine but notably thinner and plants smaller in areas where straw has overlapped (headland meets middle) there are some bare areas still with a thick straw mat present

fits this theory nicely, ie the tine of the Dale has row cleaned where as the disc drills hair pining in this case was detrimental

This all seems logical as we have a 4ha field (1st wheat) that went flat as a pancake last harvest due to it having lots of manure previously. Sod to combine which we had to do across the tramlines just to pick up the crop. The stubble was left very long because of this but the straw was removed. Then planted with 2nd wheat and its not good now at all. Cleavers are attacking it but the crop just isn't good which initially we thought lack of water because it is a bit dry but the rest of the land around it looks much better and healthier.

All we did was pan bust it then press in front of the vaderstad so we were not inverting the residue which meant the new crop (2nd wheat) was growing around the last crops residue. Im sure many people will say you should plough for a 2nd wheat but we haven't done for about 15 years but normally the stubbles are cut short and the chopped residue is mixed thoroughly using something like a Sumo, so we are moving the toxins into at least 8 inches of soil thats loosened. This year we did not do that ........

@Clive would you think about a rake?

 

[SilliamWhale]

A bit more circumstancial eveidence

2 fields of wheat on a block of land with same rotation for at least 20 years drilled same day same seed, same seed rate and same operator even and treated identically since drilling

solitice following spring oats, straw chopped both had no cultivation

first field drilled with 750a, could find evidence of hair-pining on the day second field drilled with Dale

the Dale field is much thicker and plants are taller, no thin or bare patches

750a field is fine but notably thinner and plants smaller in areas where straw has overlapped (headland meets middle) there are some bare areas still with a thick straw mat present

fits this theory nicely, ie the tine of the Dale has row cleaned where as the disc drills hair pining in this case was detrimental

But this could be allelopathy plain and simple. Rule 1 (and I break it plenty!) would be reduce amount of white straw crops followed by white straw crops especially in the Autumn.

I do W barley after WW (baled) and I get away with it generally, but spring barley doesn't really like no till much!

 

[Gourlaw]

Not sure if this is relevant, but may add to the debate.

BY R. JAMES COOK, 04/16/2013
Plant Health International

Allelopathy—the inhibition of one organism by another through production of a toxic chemical—has been a common default explanation for the poor growth of crop plants when exposed to the decomposing plant residue, usually fresh plant residue. Allelopathy has also been targeted as a means to control weeds. The connection between symptoms of injury and the presence of decomposing plant residue, including the crop’s own residue, is usually quite clear. The effect is usually then confirmed by growing the sensitive plant in soil amended with the putative toxic plant residue and comparing that plant growth with growth in the same soil without the plant residue.

Hired by the U.S. Department of Agriculture’s Agricultural Research Service in 1965 to develop a research program on root diseases and soil-borne plant pathogens of wheat, and stationed at Washington State University in Pullman, I was confronted with a long-standing explanation that wheat straw was allelopathic to the growth of wheat. This explanation dates back to the introduction of stubble-mulch farming in the North American Great Plains in the wake of the “Dust Bowl”, also known as the “Dirty Thirties.” Growers adopting this new method of farming, where the stubble and other harvest residue was left on the soil surface or mixed into the top few inches of soil, soon noticed that yields of wheat were depressed compared to the traditional complete burial by plowing.

Two competing theories emerged to explain the effect: the straw was toxic or the microorganisms responsible for decomposition of the straw also tied up the available soil nitrogen, thereby starving the crop of nitrogen. When studies in greenhouse pots revealed that wheat was severely stunted when grown in soil amended with fresh chopped wheat straw, and that the stunting effect was not eliminated by adding more nitrogen, the toxin (allelopathy) theory was accepted and would remain the focus of study for the next the 30 years, from roughly the 1950s to the 1980s, including in Australia and the UK. While no toxin was ever isolated and shown to cause the problem, the allelopathy explanation has lived on and still comes up in grower meetings and discussions to this day.

The Injurious Organisms are in the Soil not in the Straw

Two studies conducted in two different fields separated by about 70 miles in eastern Washington, both direct-seeded (no-till), confirmed that wheat yields can be depressed significantly by straw on the soil surface, but showed further that the organism(s) responsible for the yield-depressing effect of straw are in the soil and not in the straw. The study conducted on a farm near Fairfield, WA is described in more detail below, since the results were the same in both experiments.

Yields were lower and essentially the same in natural soil and fumigated covered with straw compared with natural soil left bare black. This confirms that yields of wheat after wheat can be depressed by straw on the soil surface. However, yields were 25% greater in response to soil fumigation plus added straw and, again, this increase was essentially the same whether the straw was fumigated or left natural. The highest average yield at 109 bu/A (7.57 mt/ha) occurred in plots left bare black and fumigated. The same or even more spectacular results were obtained in the experiment done near Pullman.
The take-all root disease in particular, but also Rhizoctonia root rot and Pythium root rot are common on wheat after wheat in eastern Washington, including at the site where the above experiment was conducted. All three root diseases are favored by cool moist conditions in the top few inches of soil. Removing the harvest residue by burning favors faster and greater drying and warming of the soil layer where these diseases develop, whereas covering the soil with a layer of straw would create soil conditions more favorable to these root diseases. Even soil fumigation does not completely eliminate these pathogens, the take-all pathogen in particular, which can account for the highest yield in fumigated soil left bare black.

Fresh Straw, Especially Fresh Chaff, Serves as a Stimulant for Pythium Root Rot

Pythium species, being such successful parasites of plant roots and rootlets, are ubiquitous in agricultural and garden soils if not all soils regularly colonized by roots. The investigators of toxic straw apparently had no awareness of this fact since their research, having been done with untreated soil taken from wheat fields, would have been done with Pythium present in the soil. Any study done to investigate the role of a food base such as fresh organic material on plant growth and development without accounting for a role of Pythium species will likely lead to an erroneous conclusion.



From left to right: Natural soil no added chaff; pasteurized soil plus 1% chaff by weight; natural soil plus 1% chaff; and pasteurized soil.

Pythium spores are eliminated from soil by treatment (pasteurization) with moist heat at about 45 C (about 115 F) for 20 minutes. For my experimental system under controlled conditions in a greenhouse, I used fresh wheat chaff added at 1 gm dry chaff to 100 g air-dry soil (from any wheat field) distributed in small containers, planted to wheat and watered. Wheat chaff was claimed to be particularly “toxic” to young wheat plants and to account for the so-called “combine row effect” where wheat is stunted in areas where the chaff falls behind the combine at the time of harvest (before the days of better straw spreaders).

Indeed, wheat seedlings exposed to chaff added to soil were greatly stunted and sickly yellow compared to seedling of the same age and grown in the same soil and under the same conditions but without chaff. As expected if Pythium was involved, plants grew normally and were healthy in soil pasteurized before adding natural chaff. A separate study showed that the population of Pythium species increased many-fold in response to the chaff, presumably using the chaff as a source of sugars and food base. [see Cook, R. J., C. Chamswarng, and W.-h. Tang. Influence of wheat chaff and tillage on Pythium populations and Pythium damage to wheat. Soil Biol. Biochem. 22:939-947. 1990.]

Metaxyl Fungicide Specific for Pythium and its Close Relatives Eliminates the Problem



One of my PhD students, Chiradai Chamswarng from Thialand, conducted an experiment with wheat grown to the tillering stage while exposed to 1% fresh wheat chaff added to the soil. Rather than pasteurized soil, he drenched the soil with a water-soluble chemical known as metalaxyl specifically inhibitory to Pythium and its closest relatives. He then withdrew the root balls from the pots to expose the roots present at the interface between the soil and the inside edge of the container. As seen in the photo above, the roots were white and obviously healthy and the plants were of normal height grown in soil drenched with metalaxyl but were clearly damaged and missing and the plants stunted when grown in soil drenched with water only.

Quaker Oat Meal also a Stimulant of Pythium as a Pathogen

Just as the earlier work was carried out without awareness of the ubiquitous presence of Pythium species in agricultural and garden soils, the earlier work also looked only at components of wheat straw and not other plant materials that might have served as what, in experimental science, are called controls. For one control, I used Quaker oatmeal from our kitchen cupboard, added dry to soil just as dry chaff was added, at 1 gm per 100 gm of air dry soil planted to wheat and watered. The oatmeal was every bit as “injurious” to the young wheat plants as was chaff, for the same reason: it served as a source of nutrients and food base for Pythium species.

The Oatmeal Study Works as Science Project for Students

My granddaughter, Jessica Brockmeyer–when seven years old and in the first grade–used the same experimental system I used for wheat chaff and oatmeal except she used soil from her mother’s garden sieved through quarter-inch hardware cloth to remove plant material and break up clods. She also used peas rather than wheat as her test plants, being that peas are super susceptible to damping off caused by Pythium. She did her experiment with pea seeds planted into small plastic drinking cups filled, respectively, with natural soil with or without oatmeal chopped in a coffee grinder, and soil pasteurized in a double boiler (microwave would have worked just as well or better) with or without oatmeal. She had four cups for each treatment and five pea seeds planted per cup.



Not a single pea seedling emerged from any of the four cups containing natural soil with added oatmeal (see C-1; labeled + organic matter above). In contrast, all five seedlings emerged from either heat-treated on natural soil with no added oatmeal. A few seedlings failed to emerge in pasteurized soil amended with oatmeal, presumably because of Pythium spores that escaped the heat treatment. The seeds that did not germinate were mushy and encased in soil, typical of Pythium damping off.



The fact that this experiment using a garden soil produced the same results obtained with a wheat field soil confirms the ubiquitous presence of Pythium species in soil. This experiment should work with any soil subjected to normal plant vegetation.

 

[Baling Hay]

Unfortunately this is providing more and more evidence AGAINST no till.

 

[Clive]

But this could be allelopathy plain and simple. Rule 1 (and I break it plenty!) would be reduce amount of white straw crops followed by white straw crops especially in the Autumn.

I do W barley after WW (baled) and I get away with it generally, but spring barley doesn't really like no till much!

I have always put my more patchy results of WW after oats down to allopathy but why would it be worse on the straw chapter overlaps ? and why is it better after the Dale that effectively trash cleans than it is after the 750a which doesn't ? I think Simon(s) are right and it more to do with straw break down than root exudates etc

That's not to say it might not be a combination of both straw breakdown plus alleophathy however ?

 

[Clive]

@Clive would you think about a rake?

I don't really get rakes TBH - I think they are a solution to a poor combine mostly and if I want top scratch the surface I can use a carrier very fast and cheaply to achieve that

I think I have this straw problem covered TBH by my rotation, the only problem area being wheat after oats and OSR after barley, I think a combination of straw removal, prilled lime and row cleaners will maybe sort that or possibly a move from WW after the oats to a spring wheat................TBH i'm really going of winter crops the deeper I get into all this, I can get good GMargins from spring plantings and improves soils and combat weed, disease so much easier with spring options

 

[Tractor Boy]

I don't really get rakes TBH - I think they are a solution to a poor combine mostly and if I want top scratch the surface I can use a carrier very fast and cheaply to achieve that

I think I have this straw problem covered TBH by my rotation, the only problem area being wheat after oats and OSR after barley, I think a combination of straw removal, prilled lime and row cleaners will maybe sort that or possibly a move from WW after the oats to a spring wheat................TBH i'm really going of winter crops the deeper I get into all this, I can get good GMargins from spring plantings and improves soils and combat weed, disease so much easier with spring options

Just looking at your last sentence......REALLY? You are on light soil but must get a lot more rain to come up with that statement. Our spring crops on heavy land have only had 15 mm rain now in about 6 weeks!! Moisture is just not guaranteed in this country in the spring.

 

[Clive]

Just looking at your last sentence......REALLY? You are on light soil but must get a lot more rain to come up with that statement. Our spring crops on heavy land have only had 15 mm rain now in about 6 weeks!! Moisture is just not guaranteed in this country in the spring.

A few years ago I would have agreed totally and wouldn't have a spring crop on the farm unless something had gone seriously wrong with a winter one

proper zero-til and cover crops have changed that opinion totally, there are many parts of the world where spring- harvest rainfall is much lower than ours that only grow spring crops, there is enough moisture most years, the key is building a soil, cover and a rotation that make the most of what we do get

its dry here right now still, Im still drilling today (millet). looking around today its my winter crops that need water more than anything spring sown just yet. Last year the dry weather in june / july took at least a tonne of my ww yields yet all my spring crops produced top notch yields really

On light land a drought is a disaster anyway, a spring crop disaster is just a cheaper disaster !

 

[Gourlaw]

Sorry to hit you all with these science papers, but I do think they may have relevance to this thread.

Impacts and Management of Soil Acidity under Direct Seed Systems
- Effects on Soilborne Crop Pathogens
Timothy C. Paulitz
USDA-ARS, Root Disease and Biological Control Lab, Pullman, WA 99164-6430

Soil pH can have an enormous influence on the outcome of soilborne diseases caused by crop pathogens. Some soilborne pathogens have been successfully controlled by the management of soil pH. For example, clubroot of crucifers has been controlled by liming the soil to above pH 5.7. At pH 7.8, the disease is completely checked. On the other hand, common scab of potato, caused by the actinomycete Streptomyces, can be controlled by dropping the pH of the soil below 5.2. Unfortunately, none of the soilborne pathogens of direct-seeded wheat and barley can be controlled to this extent by manipulating soil pH, nor would it be economical or wise to attempt these changes on the large acreages of cereals in the Pacific Northwest. However, cropping practices such as fertilization (the form of N) and lack of tillage will have a direct influence on soil pH. This shift in soil pH may have more subtle effects on diseases in direct-seeded crops that must be considered in any management plan.

The form of nitrogen affects soil pH in two major ways. First, the addition of ammonium forms of N tends to acidify the soil. This is due to nitrification- the oxidation of NH4+ (ammonium) to NO3- (nitrate) by soil bacteria, forming energy and H+ ions that acidify the soil. However, the form of N may also affect the pH around the root, to which the pathogen is exposed when infecting the root. This zone of soil around the root is called the rhizosphere, and from the disease perspective, this soil is more important than the bulk soil away from the root. When a plant root takes up NH4+ ions, it excretes H+ ions back to balance charges, thus acidifying the zone around the root. When a root takes up NO3-, it excretes OH- ions, making the root zone more alkaline.

Direct seeding may have two direct effects on soil pH. Because the soil is not tilled, the acidification caused by fertilizer application in the top soil layers is not diluted out by mixing with the more alkaline soil below the fertilizer zone. Thus, soil pH in the top soil layers may decrease more in direct-seeded crops compared to conventionally-tilled, at least until the buffering capacity of the plow layer is reached. On the other hand, soil organic matter increases in direct-seeded crops over time. This increases the cation exchange capacity of the soil, buffering the soil by binding H+ to the negatively charged OH and COOH groups on the organic matter. NH4+ ions will also bind to organic matter, reducing acidification by nitrification. However, the long-term outcome of soil pH in direct seeded crops in the PNW is still unclear, and probably depends on the buffering capacity of the parent soil.

How does soil pH affect diseases? Remember that disease is the outcome of three interacting components- the pathogen, the plant, and the environment. Soil pH can indirectly affect diseases by affecting any one of these components. Root diseases are caused by microscopic soilborne fungi. These organisms form a network of tiny threads, which can grow through the soil and infect plant roots. Fungi absorb food as simple molecules from organic matter or living plants. These molecules must be transported across the membrane from the outside to the inside of the cell. The fungus expends energy and uses a proton pump to transport many of these molecules across the membrane by maintaining a proton (H+) gradient. The external pH (proton concentration) can affect its ability to take up food. But, in general, only extremes of pH (greater than 7 or less than 5) reduce the growth of most fungi. Put another way- at the pH of most agriculture soils, most fungi are not pH limited in terms of growth. However, pH may influence the availability of trace nutrients such as iron, zinc or manganezse in the same way as its availability to plants is affected. Thus, fungi must work harder to get these less available nutrients.

Soil pH will also affect the host plant. If the pH is too extreme, the plant will be stressed and may be less resistant to attack by the pathogen. Soil pH may affect the composition of the root exudates, which attract the soil borne pathogen. Soil pH will also affect the availability of nutrients to the plant. Some of these nutrients may be needed for strong cell walls and resistance to fungi. For example, high levels of available calcium in more alkaline soils have been implicated in the resistance to root diseases caused by Pythium.

Finally, pH may affect the microbial populations that may hold the pathogens in check. It is well known that fungi are more active in more acid soils, while bacteria are not as adapted to these conditions. Trichoderma, a biocontrol fungus, prefers acid soils. Fluorescent pseudomonads, bacteria that have been implicated in soils suppressive to take-all, prefer more neutral pH soils. Thus, by shifting soil pH, a natural suppressiveness may be enhanced or destroyed.

In this paper, I will address six major diseases of wheat and barley, all caused by soilborne fungi. In some cases, there is research showing clear-cut evidence for a pH effect, but in other cases, the research is lacking. Because of the link between type of N fertilizer and pH, I will also discuss research on ammonium vs. nitrate fertilizers. With all root diseases, proper placement of N is also important, to enable the seedling to quickly gain access to the fertilizer and overcome the lack of absorbtive capacity caused by a lack of roots.

Take-all- (Gaeumannomyces graminis var. tritici). With this disease, the evidence is strong that take-all is more severe in alkaline than in acid soils, and that disease is reduced when ammonium forms of N are applied, as opposed to nitrate forms. (Huber and Watson, 1971, Smiley et al. 1973, MacNish, 1980, MacNish, 1988). In longer-term experiments in Australia at three different sites over 11 years, less take-all was found in plots fertilized with ammonium sulfate as aopposed to sodium nitrate. This effect is related to the pH of the rhizosphere. Smiley and Cook (1973) found the disease greatly reduced when the rhizosphere pH was below 6.6, but the correlation with bulk soil pH was poor. The rhizosphere pH was 5.5 for wheat supplied with ammonium nitrogen was 5.5, compared to 7.5 for plants supplied with nitrate. The best control occurred with ammonium sulfate, and the addition of lime negated the control. Take-all decline, a natural suppressiveness associated with wheat monoculture, takes longer to establish in more alkaline soils (Cook and Baker, 1983).

Rhizoctonia bare patch and root rot (Rhizoctonia solani AG-8). There is not much information on the effect of N or pH on Rhizoctonia root rots of cereals. Most studies on Rhizoctonia root rots of broad leaf crops have shown that NO3-N results in less disease compared to NH4-N fertilizers (Huber and Watson, 1974). The same effect was seen on sharp eyespot of wheat, caused by R. cerealis. MacNish, an Australian pathologist, looked at the effects of N application on bare patch in conventional and direct-seeded wheat. He found that cultivation reduced bare patch, something that has been shown by other researchers. But the application of N also reduced bare patch in zero-tilled soil., and ammonium sulfate resulted in patch development than sodium nitrate (MacNish, 1985). However, research by Pumphrey et al. (1987) in Pendleton found that N application and timing of application had no effect on bare patch. They used ammonium sulfate at planting and ammonium nitrate at late tillering.

Smiley et al. (1996) did a 3-year study in the long-term plots at Pendleton, looking at different rotations, tillage and burning. In the wheat-fallow, they found that application of N increased the incidence of Rhizoctonia root rot. They applied, 0, 40, or 80 lbs/acre and found more disease at 40, compared to 80 lbs/acre. MacNish (1988), in long-term cropping systems study in Australia, found that N application had no effect on Rhizoctonia root rot. It is interesting that the ammonium reduced soil pH at all sites, but that Rhizoctonia declined to almost nothing after 7-9 years of continuous wheat cropping. This may be a case of development of natural suppressiveness developing. In a closely related disease on turfgrass, brown patch caused by R. solani, plots that received urea generally had less disease than the nitrate-treated plots (Fidanza and Dernoeden, 1996a). Low soil pH was weakly correlated with lower disease levels in one trial in 1993. This may be due to the sulfur acidifying the soil, rather than acidification from the ammonium. But in other trials (Fidanza and Dernoeden, 1996b), there was no correlation with soil pH. The take-home message seems to be lots of conflicting information with no rule of thumb. The effect of fertilizer type and soil pH do not appear to be major for this disease, unlike for take-all and Fusarium crown rot. However, the effect may be very site specific. There is no literature on the effect of pH on R. oryzae, which is widespread in eastern Washington (Paulitz, unpublished).

Pythium seedling and root rot- (Pythium spp). Pythium is another disease on which there is not much literature on pH effects in the field. There have been some studies in the lab, showing that at pH 4.8, fewer zoospores attach to the root than at pH 6.0. (Huyang and Tu, 1998). Pythium produces motile spores that can swim through wet soil and attach to the root to infect it. The most detailed study with relevance to the Pacific Northwest was done by a student of R. J. Cook's in the early 90s (Fukui et al. 1994). He looked at the disease-producing activity of different inoculum levels of P. ultimum, in both pasteurized and natural soils. He adjusted the pH of the natural soils to 4.3-7.6 with sulfuric acid or lime. The optimum disease activity was from pH 5.0-5.5. There was a slight decline in disease from pH 5.5 to 6.5, but above pH 6.5, the disease activity dropped significantly. In one soil where the pH was decreased to 4.3, disease also declined significantly. The take-home message on Pythium and pH is probably similar to Rhizoctonia- in the pH ranges of our soils, Pythium is not limited. In fact, Pythium has optimal activity at the pH ranges of soil that are acidified by ammonium fertilizers. The literature on N effects on Pythium is also limited. Most of the work has been done with the use of organic amendments to suppress Pythium. Pythium is very sensitive to microbial competition, and organic amendments often increase microbial activity in the soil. Smiley et al. (1996) found Pythium root rot was more prevalent in sites with inorganic N fertilizers, as opposed to those fertilized with cow manure or pea vines.

Fusarium foot rot or crown rot (Fusarium pseudograminearum and F. culmorum). Most growers are well aware that this disease is favored by increased nitrogen fertilization and drought stress. The effect of the type of N on this disease is well-known, based on work done by Cook and Pappendick in the early 70s. Applications of NH4-N increase disease severity and incidence, while NO3-N fertilizers decrease the disease (Smiley et al. 1972). This is similar to Fusarium wilt diseases, which are suppressed by alkaline soils and nitrate fertilizers (Nelson et al.1981). Smiley et al. (1996) also found a strong correlation between crown rot and N application, and the disease was inversely proportional to soil pH, at least in the range measured (4.3 to 5.3).

Cephalosporium stripe (Cephalosporium gramineum) This is a disease where soil pH has a dramatic influence. This soilborne vascular pathogen is more damaging in acid soils with high moisture. It produces single-celled spores that infect roots wounded by winter freezing and soil heaving. In a series of studies by Tim Murray at WSU, he showed that the germination of spores is not affected by pH (Blank and Murray, 1998), but the production of spores on wheat straw buried in the soil was greater at acid pH (Murray and Walter, 1991). Disease increased 5-fold when soil pH decreased from 7.5 to 4.5. The isolation of the pathogen from crown roots was greaterless at pH 6.7 to 7.2 than at pH 4.7 to 5.9 (Stiles and Murray, 1996). Liming the soil to increase soil pH from 5.1-5.3 to >6.0 decreased this disease two out of four years, and there was a significant correlation between soil pH and infected stems (Murray et al. 1992).

Eyespot of wheat (Pseudocercosporella herpotrichoides). Only one study has been done on the effect of N and pH on this disease, with trends similar to that of Fusarium crown rot. In a study on winter wheat on wheat-fallow, eyespot incidence increased 2-3 fold when 160 lbs/acre of N was applied, compared to the non-fertilized plot (Smiley et al. 1996). This can be explained by the enhanced canopy growth, like planting early, which is well known to favor eyespot foot rot of wheat.

Conclusions

In conclusion, diseases caused by soilborne pathogens of wheat and barley can be classified into two groups- those that are not influenced greatly by pH or type of nitrogen fertilizer, and those that are. The first group includes the root rotting pathogens Pythium and Rhizoctonia. These are considered to be generalist types of pathogens that quickly kill and rot the plant tissue. The second group includes the crown rotting pathogens Fusarium and Gaeumannomyces (take-all). These initially infect and colonize the root without causing massive tissue death, and later move into the crown when the plant is older. These two diseases show opposite trends- take-all is reduced under acid conditions, while Fusarium crown rot seems to be increased. One could speculate that increased soil acidification may increase the risk of Fusarium crown rot, although N levels and drought stress are probably stronger risk factors. One can also speculate that liming the soil will increase take-all. Cephalosporum stripe, a vascular disease, is also influenced by pH and N, similar to many other vascular diseases. Liming the soil will decrease the severity of this disease. Thus, the risk of soilborne pathogens in wheat and barley may be influenced by the potential shift of soil pH in direct-seeded systems, with the different mix of diseases depending on the degree and direction of the pH shift in response to the form of nitrogen, accumulation of organic matter, and whether lime is used.

 

[Gourlaw]

Once again this paper is highlighting how higher ph helps alleviate the problem and how fert placement may help. However, I may be barking up the wrong tree!

Symptoms of Pythium Damage in the Field

Because of the ubiquitous presence of Pythium species in soil, virtually all plants are exposed to infection by one or more species starting with seed germination in the soil and continuing on the roots through plant development to adult status and maturity. Only when the soil drains and dries to a moisture content less than field capacity does Pythium activity as a seedling and root parasite begin to subside or halt.

Pythium species survive in soil as thick-walled spores that can be counted using an old technique known as dilution plating of infested soil on a selective medium. Essentially all wheat field soils tested so far in the Inland Northwest have counts of 200 Pythium propagules per gram of soil, and the average propagule count is 350-400 per gram, nearly all of which is in the top 4-6 inches of soil (Cook et al, 1990). Some eastern Washington fields in a standard winter wheat/spring barley/pea 3-year rotation have registered 1000 propagules of Pythium per gram of soil. Independent studies indicate that at 200 Pythium propagules per gram of soil is above the threshold needed to saturate the available infection sites on plants so that the amount of damage is entirely a function of the soil environment and management of this disease must focus on plant protection or helping the plant tolerate or recover from infections.

Wheat seeds planted without protection from Apron, Thiram, or other appropriate fungicide applied as a seed treatment become infected within the first 24-48 hours after planting into moist soil. The infection occurs in the embryo where the parasite is then positioned to obtain nourishment from sugars mobilized from the endosperm (Hering et al., 1987). Seedling emergence still occurs, but the seedlings may be spindly, stunted, or the first true leaf to form on the seedling will be twisted, cupped, or unusually short. These symptoms can be explained on the basis of a combination of embryo damage and starvation of the seedling owing to the use of endosperm sugars by Pythium. Low seedling vigor because of Pythium infection in the seedling stage results in less tillering, retardation of plant development, and less yield, although test weight may be greater because of water left unused by the smaller crop.

With peas, garbonzo beans, corn, or other large seeded crops, seeds planted without protection against Pythium are likely to rot in the soil without producing a seedling, or the seedling may emerge but then die. There are many names given to this phase of Pythium attack on germinating seeds, including seed rot, preemergence seed decay, damping off, and seedling blight.

Seed treatments are covered in a subsequent section of this paper; suffice to say here that with seed treatment, this kind of Pythium damage to crops is largely prevented.

Recognition of Pythium root rot based on symptoms is difficult. One problem is that the root tissues infected, especially fine rootlets and root hairs, are quickly converted to spores or other biomass of the pathogen, leaving little or nothing left for diagnosis. Washed roots are easier to examine than roots still covered with soil, but this usually also removes all remains of Pythium-infected roots. For wheat and barley, this can produce what I call picture-wire roots-where the main roots, stripped of laterals and hairs, resemble the fine wire used to hang pictures.

Like many investigators before me, I have used soil fumigation as a research tool to reveal what wheat and barley plants look like without the early damage to seedlings and continued root pruning caused by Pythium (Cook et al., 1987). Extensive studies going back 50 years when soil fumigants came into use after World War II have consistently pointed to control of ubiquitous Pythium as one of the major reasons for the universal increased growth and yield response of crops to soil fumigation. Wheat grown in fumigated soil in the high-precipitation zones of eastern Washington, for example, produces 20-25% more tillers, heads 2-3 days earlier, stands 2-3 inches taller when at full adult-plant height, and is more uniform in height compared to wheat grown in adjacent plots with soil left untreated. Drenching the soil with metalaxyl, the active ingredient of Apron, has produced the same increased grown response noted with soil fumigation (Cook et al., 1980), providing further evidence for the kind of symptoms produced by Pythium on wheat in the field. Not surprisingly, because of the ubiquitous presence of Pythium species in soil, every plant in nontreated soil is affected by Pythium more or less the same so that, without the comparison of how healthy plants should look, we accept plants with Pythium damage as normal "healthy" plants.

Soil Conditions Favorable to Pythium

Pythium species become active only when soil moisture is at or exceeds field capacity. Research by Allmaras and others (1988) showed at Pendleton that the tillage pan 4-6 inches deep becomes an impediment to water infiltration during periods of rain or snow melt, which then results in periods of saturated soil and more Pythium damage. From this conclusive research, we can speculate that the improved drainage of soil after a few years of direct seeding will lower the risk of Pythium root rot.

Not surprisingly, the Pythium species adapted to Northwest soils are mostly low-temperature species. The Pythium species in warmer parts of the world are adapted to high soil temperatures. Of two common species of Pythium in Northwest wheat field soils, P. ultimum is active down at soil temperatures down 10 C (50 F) and P. irregulare is active at soil temperatures down of 5 C (41 F). While the cool-season crops grown in this region are also adapted to these low temperatures, some defenses needed to prevent the "common cold" from becoming "pneumonia" (Vijiyan et al., 1998) are thought to be compromised, thereby resulting in predisposition of the crop to greater Pythium damage at temperatures below 40 F.

The favoring effects of cold wet soil on Pythium damage are one reason for the increased growth and yield response of direct-seeded wheat and barley to stubble burning. Bare black soil warms and dries faster, which favors the crop over the pathogen. While necessary in some situations, the goal of direct seeding and certainly the goal of the research programs in support of direct seeding must be to manage root diseases without depending on stubble burning.

Research done by graduate student Ryo Fukui in the early 1990s used a laboratory test to precisely measure the soil physical and chemical factors most favorable to Pythium damage (Fukui et al., 1994). In this system, he maintained soil water at the ideal level for Pythium so as to then measure other factors limiting to parasitism by Pythium species. Two soil factors stood out as favorable to Pythium in addition to wet soil. These were high clay content and low soil pH. We speculate that both of these soil factors favor Pythium indirectly rather than directly. For example, high clay content also means that the soil holds more water when at field capacity or higher. More water on a soil volume basis also then means greater diffusivity of seed and root exudates to distances outward in the soil to reach and stimulate more germination of Pythium spores sitting dormant in the soil. The low pH was shown to have a suppressive effect on microorganisms that otherwise were competitors of Pythium in the soil. When Fukui added antibiotics to soil to suppress competitors, Pythium was then just as active in soils at higher pH values.

These results fit with field observations that point to Pythium damage as a problem on wheat, barley, and the grain legumes mainly in far eastern and southeastern Washington and adjacent northern Idaho where clay contents of the soils and annual precipitation are highest and soil pH is generally lowest.

Crop Rotation

Because all plants are hosts of Pythium species, crop rotation is of little or no use in management of the diseases caused by these soilborne pathogens. Only periods without plants, such as bare fallow, are likely to provide the kind of break needed to lower the potential for damage on a subsequent crop. This is of little use in the Northwest since soil conditions are already least favorable in areas where fallow is practiced, owing to the relatively low clay content, dry conditions, and higher pH values of these soil. Further, as pointed out above, the amount of Pythium in our soils is commonly double the threshold inoculum needed for maximum damage, and achieving a 50% or greater reduction in Pythium load in the soil is highly unlikely during a 12-13 month fallow. The dormant spores of Pythium can last in soil for considerable periods of time.

We have some evidence that different crops favor different Pythium species, so that rotation of crops also rotates the species of Pythium available for infection of the next crop. Research by graduate student David Ingram indicates that P. irregulare thrives on barley, while P. ultimum thrives on peas, and that both of these species do more or less equally well on wheat (Ingram and Cook, 1990). Thus, a 2-year wheat/pea rotation could be expected to select for P. ultimum while a wheat/barley/pea rotation could be expected to select for both P. ultimum and P. irregulare. There is also evidence from the scientific literature that Pythium species compete with each other and that some weaker parasites can preempt infection by stronger parasites. Sorting this out becomes very complex.

Fertilizer Placement

Placement of fertilizer directly under the seed, or below and slightly to one side of the seed at the time of planting offers one of the best management tools for all root diseases but especially Pythium root rot. Roots without laterals or striped of hairs cannot reach far for phosphorus and other relatively immobile nutrients. Our method of fertilization in fields where Pythium root rot and other root diseases are important requires that the nutrients be made easily accessible to the roots rather than expecting the roots to grow to the nutrients.

The benefits of fertilizer placement have been demonstrated using soil fumigation. In soil with root diseases controlled by fumigation, yields of spring barley and spring wheat were the same whether the fertilizer is banded below or below and 6 inches to one side of the seed, but in adjacent plots of nonfumigated soil, yields dropped when roots had to reach more than 2-3 inches to one side of the seed row to access a band of fertilizer (Cook et al., 2000). This is why, when using a two pass system of direct seeding, where nitrogen is applied in one pass, possibly in the fall for spring seeding, and planting is done with a second pass, that some starter be applied at the time of planting. Placement of phosphorus in the seed row may be just as useful as banding.

Conclusions:

Pythium damages crops either though infection of the embryos of germinating seed or through destruction of fine rootlets and root hairs. Best protection of germinating seeds is achieved with seed treatments that include Apron or Apron XL Older products such as Thiram are also effective. Seed treatments improve seedling vigor and can produce, on average and across the Inland Northwest, an additional 2-4 bu/A. However, seed treatments do not provide protection against the continuing attack of roots by Pythium. The other important tool for wheat and barley is to use fresh seed, or seed no older than 1-year, so as to minimize susceptibility and maximize ability of the seedling to tolerate Pythium infection.

Pythium species are most active as seedling and root pathogens in soils with moisture contents at field capacity or above, and in soils high in clay content and low in soil pH. For this reason, the damage to crops caused by these soilborne pathogens occurs mainly in far eastern and southeastern Washington and adjacent Idaho. Soils in these areas have, on average, about double the amount of spore load to produce maximum damage, and therefore the amount of damage is a reflection of soil environment. The ubiquitous and uniform presence of Pythium species in Inland PNW soils, especially in the higher rainfall areas with high clay and low pH soils, can explain why, for wheat and barley, the chronically poor tillering, stunting, and delayed maturity caused by this pathogen is so uniform in the fields that we have come to accept crops with Pythium-incited damage as the normal "healthy" crops.

Cold wet trashy seedbeds typical of direct-seed systems will tend to favor greater damage caused by Pythium. This is because of the favorable effects of low temperature and high soil moisture on Pythium and possibly also the stimulatory effects of fresh wheat straw on Pythium as a saprophyte in soil. On the positive side, we can expect that improved soil drainage in response to structural changes in soil with the transition from conventional to no tillage will greatly help to limit Pythium damage. Also, the use of direct-seed drills that place fertilizer directly under the seed, or that include starter fertilizer below or with the seed, is helping the crops tolerate Pythium root rot, through making nutrients more readily accessible to diseased roots.

 

[Tractor Boy]

A few years ago I would have agreed totally and wouldn't have a spring crop on the farm unless something had gone seriously wrong with a winter one

proper zero-til and cover crops have changed that opinion totally, there are many parts of the world where spring- harvest rainfall is much lower than ours that only grow spring crops, there is enough moisture most years, the key is building a soil, cover and a rotation that make the most of what we do get

its dry here right now still, Im still drilling today (millet). looking around today its my winter crops that need water more than anything spring sown just yet. Last year the dry weather in june / july took at least a tonne of my ww yields yet all my spring crops produced top notch yields really

On light land a drought is a disaster anyway, a spring crop disaster is just a cheaper disaster !

I know ours is a Claydon, so not true no til, but it is working conserving moisture and improving structure. Rotation I'm coming round to for grass weed problems, but I still can't get my head round cover crops on heavier soil.

 

[Clive]

I know ours is a Claydon, so not true no til, but it is working conserving moisture and improving structure. Rotation I'm coming round to for grass weed problems, but I still can't get my head round cover crops on heavier soil.

I like strip till and think it has a big place on uk farms but it's not the same as zero-till agronomically at all IMO

It's more single pass mintil really, and I wouldn't be as confident about spring crops under min or strip till as I am with zero-til / cover crops

 

[RushesToo]

On light land a drought is a disaster anyway, a spring crop disaster is just a cheaper disaster !

If you are on light soil then there are good reasons to go no till. If you plough you expose more area to the wind and it will dry the soil very effectively. This perhaps needless to say is bad on light soil - although quite desirable on heavy.

No till, and keeping organic matter in the soil makes you able to withstand drought better - a useful tweet here:

Shows why you want to keep the organic matter.

The challenge is to keep the organic matter, not disturb the soil and suppress pathogens. This is one of the challenges that has to be overcome, and yes there are many more.

 

[Andy Howard]

Once again this paper is highlighting how higher ph helps alleviate the problem and how fert placement may help. However, I may be barking up the wrong tree!

Symptoms of Pythium Damage in the Field

Because of the ubiquitous presence of Pythium species in soil, virtually all plants are exposed to infection by one or more species starting with seed germination in the soil and continuing on the roots through plant development to adult status and maturity. Only when the soil drains and dries to a moisture content less than field capacity does Pythium activity as a seedling and root parasite begin to subside or halt.

Pythium species survive in soil as thick-walled spores that can be counted using an old technique known as dilution plating of infested soil on a selective medium. Essentially all wheat field soils tested so far in the Inland Northwest have counts of 200 Pythium propagules per gram of soil, and the average propagule count is 350-400 per gram, nearly all of which is in the top 4-6 inches of soil (Cook et al, 1990). Some eastern Washington fields in a standard winter wheat/spring barley/pea 3-year rotation have registered 1000 propagules of Pythium per gram of soil. Independent studies indicate that at 200 Pythium propagules per gram of soil is above the threshold needed to saturate the available infection sites on plants so that the amount of damage is entirely a function of the soil environment and management of this disease must focus on plant protection or helping the plant tolerate or recover from infections.

Wheat seeds planted without protection from Apron, Thiram, or other appropriate fungicide applied as a seed treatment become infected within the first 24-48 hours after planting into moist soil. The infection occurs in the embryo where the parasite is then positioned to obtain nourishment from sugars mobilized from the endosperm (Hering et al., 1987). Seedling emergence still occurs, but the seedlings may be spindly, stunted, or the first true leaf to form on the seedling will be twisted, cupped, or unusually short. These symptoms can be explained on the basis of a combination of embryo damage and starvation of the seedling owing to the use of endosperm sugars by Pythium. Low seedling vigor because of Pythium infection in the seedling stage results in less tillering, retardation of plant development, and less yield, although test weight may be greater because of water left unused by the smaller crop.

With peas, garbonzo beans, corn, or other large seeded crops, seeds planted without protection against Pythium are likely to rot in the soil without producing a seedling, or the seedling may emerge but then die. There are many names given to this phase of Pythium attack on germinating seeds, including seed rot, preemergence seed decay, damping off, and seedling blight.

Seed treatments are covered in a subsequent section of this paper; suffice to say here that with seed treatment, this kind of Pythium damage to crops is largely prevented.

Recognition of Pythium root rot based on symptoms is difficult. One problem is that the root tissues infected, especially fine rootlets and root hairs, are quickly converted to spores or other biomass of the pathogen, leaving little or nothing left for diagnosis. Washed roots are easier to examine than roots still covered with soil, but this usually also removes all remains of Pythium-infected roots. For wheat and barley, this can produce what I call picture-wire roots-where the main roots, stripped of laterals and hairs, resemble the fine wire used to hang pictures.

Like many investigators before me, I have used soil fumigation as a research tool to reveal what wheat and barley plants look like without the early damage to seedlings and continued root pruning caused by Pythium (Cook et al., 1987). Extensive studies going back 50 years when soil fumigants came into use after World War II have consistently pointed to control of ubiquitous Pythium as one of the major reasons for the universal increased growth and yield response of crops to soil fumigation. Wheat grown in fumigated soil in the high-precipitation zones of eastern Washington, for example, produces 20-25% more tillers, heads 2-3 days earlier, stands 2-3 inches taller when at full adult-plant height, and is more uniform in height compared to wheat grown in adjacent plots with soil left untreated. Drenching the soil with metalaxyl, the active ingredient of Apron, has produced the same increased grown response noted with soil fumigation (Cook et al., 1980), providing further evidence for the kind of symptoms produced by Pythium on wheat in the field. Not surprisingly, because of the ubiquitous presence of Pythium species in soil, every plant in nontreated soil is affected by Pythium more or less the same so that, without the comparison of how healthy plants should look, we accept plants with Pythium damage as normal "healthy" plants.

Soil Conditions Favorable to Pythium

Pythium species become active only when soil moisture is at or exceeds field capacity. Research by Allmaras and others (1988) showed at Pendleton that the tillage pan 4-6 inches deep becomes an impediment to water infiltration during periods of rain or snow melt, which then results in periods of saturated soil and more Pythium damage. From this conclusive research, we can speculate that the improved drainage of soil after a few years of direct seeding will lower the risk of Pythium root rot.

Not surprisingly, the Pythium species adapted to Northwest soils are mostly low-temperature species. The Pythium species in warmer parts of the world are adapted to high soil temperatures. Of two common species of Pythium in Northwest wheat field soils, P. ultimum is active down at soil temperatures down 10 C (50 F) and P. irregulare is active at soil temperatures down of 5 C (41 F). While the cool-season crops grown in this region are also adapted to these low temperatures, some defenses needed to prevent the "common cold" from becoming "pneumonia" (Vijiyan et al., 1998) are thought to be compromised, thereby resulting in predisposition of the crop to greater Pythium damage at temperatures below 40 F.

The favoring effects of cold wet soil on Pythium damage are one reason for the increased growth and yield response of direct-seeded wheat and barley to stubble burning. Bare black soil warms and dries faster, which favors the crop over the pathogen. While necessary in some situations, the goal of direct seeding and certainly the goal of the research programs in support of direct seeding must be to manage root diseases without depending on stubble burning.

Research done by graduate student Ryo Fukui in the early 1990s used a laboratory test to precisely measure the soil physical and chemical factors most favorable to Pythium damage (Fukui et al., 1994). In this system, he maintained soil water at the ideal level for Pythium so as to then measure other factors limiting to parasitism by Pythium species. Two soil factors stood out as favorable to Pythium in addition to wet soil. These were high clay content and low soil pH. We speculate that both of these soil factors favor Pythium indirectly rather than directly. For example, high clay content also means that the soil holds more water when at field capacity or higher. More water on a soil volume basis also then means greater diffusivity of seed and root exudates to distances outward in the soil to reach and stimulate more germination of Pythium spores sitting dormant in the soil. The low pH was shown to have a suppressive effect on microorganisms that otherwise were competitors of Pythium in the soil. When Fukui added antibiotics to soil to suppress competitors, Pythium was then just as active in soils at higher pH values.

These results fit with field observations that point to Pythium damage as a problem on wheat, barley, and the grain legumes mainly in far eastern and southeastern Washington and adjacent northern Idaho where clay contents of the soils and annual precipitation are highest and soil pH is generally lowest.

Crop Rotation

Because all plants are hosts of Pythium species, crop rotation is of little or no use in management of the diseases caused by these soilborne pathogens. Only periods without plants, such as bare fallow, are likely to provide the kind of break needed to lower the potential for damage on a subsequent crop. This is of little use in the Northwest since soil conditions are already least favorable in areas where fallow is practiced, owing to the relatively low clay content, dry conditions, and higher pH values of these soil. Further, as pointed out above, the amount of Pythium in our soils is commonly double the threshold inoculum needed for maximum damage, and achieving a 50% or greater reduction in Pythium load in the soil is highly unlikely during a 12-13 month fallow. The dormant spores of Pythium can last in soil for considerable periods of time.

We have some evidence that different crops favor different Pythium species, so that rotation of crops also rotates the species of Pythium available for infection of the next crop. Research by graduate student David Ingram indicates that P. irregulare thrives on barley, while P. ultimum thrives on peas, and that both of these species do more or less equally well on wheat (Ingram and Cook, 1990). Thus, a 2-year wheat/pea rotation could be expected to select for P. ultimum while a wheat/barley/pea rotation could be expected to select for both P. ultimum and P. irregulare. There is also evidence from the scientific literature that Pythium species compete with each other and that some weaker parasites can preempt infection by stronger parasites. Sorting this out becomes very complex.

Fertilizer Placement

Placement of fertilizer directly under the seed, or below and slightly to one side of the seed at the time of planting offers one of the best management tools for all root diseases but especially Pythium root rot. Roots without laterals or striped of hairs cannot reach far for phosphorus and other relatively immobile nutrients. Our method of fertilization in fields where Pythium root rot and other root diseases are important requires that the nutrients be made easily accessible to the roots rather than expecting the roots to grow to the nutrients.

The benefits of fertilizer placement have been demonstrated using soil fumigation. In soil with root diseases controlled by fumigation, yields of spring barley and spring wheat were the same whether the fertilizer is banded below or below and 6 inches to one side of the seed, but in adjacent plots of nonfumigated soil, yields dropped when roots had to reach more than 2-3 inches to one side of the seed row to access a band of fertilizer (Cook et al., 2000). This is why, when using a two pass system of direct seeding, where nitrogen is applied in one pass, possibly in the fall for spring seeding, and planting is done with a second pass, that some starter be applied at the time of planting. Placement of phosphorus in the seed row may be just as useful as banding.

Conclusions:

Pythium damages crops either though infection of the embryos of germinating seed or through destruction of fine rootlets and root hairs. Best protection of germinating seeds is achieved with seed treatments that include Apron or Apron XL Older products such as Thiram are also effective. Seed treatments improve seedling vigor and can produce, on average and across the Inland Northwest, an additional 2-4 bu/A. However, seed treatments do not provide protection against the continuing attack of roots by Pythium. The other important tool for wheat and barley is to use fresh seed, or seed no older than 1-year, so as to minimize susceptibility and maximize ability of the seedling to tolerate Pythium infection.

Pythium species are most active as seedling and root pathogens in soils with moisture contents at field capacity or above, and in soils high in clay content and low in soil pH. For this reason, the damage to crops caused by these soilborne pathogens occurs mainly in far eastern and southeastern Washington and adjacent Idaho. Soils in these areas have, on average, about double the amount of spore load to produce maximum damage, and therefore the amount of damage is a reflection of soil environment. The ubiquitous and uniform presence of Pythium species in Inland PNW soils, especially in the higher rainfall areas with high clay and low pH soils, can explain why, for wheat and barley, the chronically poor tillering, stunting, and delayed maturity caused by this pathogen is so uniform in the fields that we have come to accept crops with Pythium-incited damage as the normal "healthy" crops.

Cold wet trashy seedbeds typical of direct-seed systems will tend to favor greater damage caused by Pythium. This is because of the favorable effects of low temperature and high soil moisture on Pythium and possibly also the stimulatory effects of fresh wheat straw on Pythium as a saprophyte in soil. On the positive side, we can expect that improved soil drainage in response to structural changes in soil with the transition from conventional to no tillage will greatly help to limit Pythium damage. Also, the use of direct-seed drills that place fertilizer directly under the seed, or that include starter fertilizer below or with the seed, is helping the crops tolerate Pythium root rot, through making nutrients more readily accessible to diseased roots.

I think this is spot on and confirms what I have seen this year. In WW after spring oats some fields had starter which included N, P and sugars/molasses and beneficial biological. These fields are streets ahead of others that did not have starter. No problem with straw overlaps etc. I am going to carry on cutting high and applying starter after any white straw crop. It has worked well this year and makes sense to me. See what next year brings.

 

[Alistair McLaren]

I think we have seen the effects mentioned in the OP by @Simon Chiles in an area of SB that was planted by a Cross Slot?

This area was thick with strong AMG (spray miss from Autumn) plants on clay that was sprayed off a few days before planting. It took a lot longer to emerge in this area than the rest and is still behind now but is slowly catching up.
We're going to be planting a SB and Vetch mix in similar soil after PP once the silage cut has been taken off, again with the Cross Slot, what rate of lime would be recommended to combat this. Was thinking along the lines of mixing it in with seed.

 

[SilliamWhale]

@Alistair McLaren - i get this sort of thing to now and again. Spring barley is a sod for it.

 

[Andy Howard]

This is an exert from Phil wheeler and Crop Services International. It was also in Acres USA recently. Liming plus pre em in one pass. Would to see whether this has any real evidence!
WEED CONTROL: CSI’s original weed control formula was 2 gallons of molasses and 2 gallons of liquid Calcium chelate in 20 gallons of water sprayed on top of the soil as soon as possible after last disturbance of soil by any implement including the planter. This works because the available Calcium tells the grass seeds that they are not needed and the molasses, which activates bacteria that release Phosphorus, tells the broadleaf weed seed that they are not needed. Astute farmers rigged up booms behind the planter connected to a saddle tank to plant and treat all in one pass. Separate passes must be as soon as possible and after 24 hours, forget It! You can also use the formulas at reduced rates to keep suppression going through the season in low growing crops.

CSI now has at least 4 options for the material used with the 2 gallons of molasses: Regular liquid Calcium chelate & organic liquid Calcium chelate (used at the 2 gallon rate) & PhosCal 22 liquid and Premium Cal 33 liquid (used at the 2 qt rate). A California rice grower reported total control of Water Grass in one of his paddies using the above

 

[Simon Chiles]

I think we have seen the effects mentioned in the OP by @Simon Chiles in an area of SB that was planted by a Cross Slot?View attachment 44254
View attachment 44256
This area was thick with strong AMG (spray miss from Autumn) plants on clay that was sprayed off a few days before planting. It took a lot longer to emerge in this area than the rest and is still behind now but is slowly catching up.
We're going to be planting a SB and Vetch mix in similar soil after PP once the silage cut has been taken off, again with the Cross Slot, what rate of lime would be recommended to combat this. Was thinking along the lines of mixing it in with seed.

PM me your phone no and I'll go through it with you.

 

[mikep]

I think we have seen the effects mentioned in the OP by @Simon Chiles in an area of SB that was planted by a Cross Slot?View attachment 44254
View attachment 44256
This area was thick with strong AMG (spray miss from Autumn) plants on clay that was sprayed off a few days before planting. It took a lot longer to emerge in this area than the rest and is still behind now but is slowly catching up.
We're going to be planting a SB and Vetch mix in similar soil after PP once the silage cut has been taken off, again with the Cross Slot, what rate of lime would be recommended to combat this. Was thinking along the lines of mixing it in with seed.

Funny old world, I took this (very poor) photo of oats drilled through an almost pure stand of AMG as it was the best part of the field. Will be interesting to see how it goes.

 

[Richard III]

I always see a problem here if I drill into AMG or recently sprayed of couch grass, however I have yet to see a problem drilling into chopped straw with my Sim-Tec. This thread has got me worried, as I regularly drill rape and cover crops into heavy chopped straw in wet conditions.

Below is a picture of last years rape emerging through the straw, drilled at 30cm spacing.

The chopper on my combine doesn't seem to chop very well so I was planning to fit new blades this year, I'm not so sure now. No one else chops straw around here, so I have nothing to compare to, what do people think of the chop length? May be I've just been lucky so far.