Influence of Cutting Height on Stubble Management
Written by Frederic Thomas, TCS Magazine n°95. November/December 2017
The experiments and measurements that follow were carried out by Étienne Mignot (engineering student) on the farm of David Guy in Loire-Atlantique (sky France).
In order to observe the quality of emergence and the development of machinery, a variety of plants were sown with a (EasyDrill) disk drill as soon as the harvest was completed (July 10, 2017) with 3 modes of management of crop residues: high stubble (cutting at 40 cm), short straw rolled (8 cm) and rolled short straw followed by shallow stubble cultivation (5 cm deep).
The crops observed are mustard, peas and buckwheat, which serve as indicators; the other plants, according to their typology, had quite similar reactions and developments. These 3 species were used for these reasons - Mustard is often the most common “minimum cover” because it is cheap with the guarantee of good establishment; Feed pea is a legume which fixes nitrogen and it is logically a cover that must, in fact, be less sensitive to possible problems in summer after harvest. (NB In France of course !) Buckwheat was chosen as a cover that emerges quickly in summer but also as it is a commonly used species in catch cropping. In addition in 2017, spring and summer were extremely dry in the Loire Atlantique: 9 mm between sowing and first emergence, only 8 mm in the first half of August and 21 mm at the end of the month.
The dynamics of emergence
These particular conditions, which correspond more to what the majority of farmers may normally encounter in the area, have certainly amplified the differences and have highlighted the pitfalls in terms of summer cover establishment. Not surprisingly (see Figure 1), it is in the ‘rolled straw’ that the emergence is lowest, all species combined, while the ‘high stubble’ is similar. This observation confirms the difficulty of cutting through a “mattress” of dry crop residue just after harvest. The ‘hairpinning’ of the straw in the furrow is not a fable but a reality.
Stubble rolled is shown to be the worst option. On the other hand, conservation stubble cut high shows an interesting solution to protect seedlings at this time and in these conditions. As the flea beetles attacked very early in cruciferous crops this summer, the straw height seems to have disturbed them (Figure 2). Indeed, only 25% mustard seedlings were affected in the high stubble while 68% were attacked with rolled stubble and 85% in the cultivated version. This is a comforting observation on the effect of companion plants in rapeseed: from the moment they cover and even hide the seedling, some pests are avoided. It also confirms that healthy rape seedlings that grow quickly are a lot less affected.
Above Left: Mustard August 28th : except for height differences that remain important (36 cm high stubble, 28 cm in short stubble and 31 cm in the cultivated area), this observation shows up a strong difference in growth stage. The ‘high stubble’ has a bigger leaf surface area and a much larger biomass than the other two and has very few flowers. This difference in appearance confirms that in the ‘high stubble’ the plant has developed well in better conditions and with less stress, particularly related to nitrogen, as opposed to the others. Above centre and right: Peas and Buckwheat on August 28th: As shown in this picture taken on August 28, even peas, (legumes) are affected by the stubble height. in the ‘high stubble’, they have about 86 leaves on average with a lot of tendrils against 54 for the shorter stubble and 48 for peas in the cultivated area. It’s as if the difference achieved at sowing and emergence had continued to grow. The vegetation gap is equally impressive with the buckwheat that has reached the flowering stage.
Early developments A first observation, 3 weeks after sowing, the differences in techniques are already apparent. The establishment is generally better in the high cut stubble, then that seedlings are much weaker in straws rolled with or without stubble cultivation. The difference is more obvious with the peas. The ‘High stubble’ already shows thirty or so shoots with the appearance of the first tendrils, while in the shorter stubble the number of leaves goes down to 24 and even fall to 20 in the rolled straw.
A beautiful demonstration which confirms that the peas enjoy the companion crop, giving protection but also supports on which they can grab early. The difference in height of the cover also makes a big difference for buckwheat in favour of stubble cut at 40 cm. Measurements made 2 weeks later in the middle of August reinforce these first observations with big differences especially for peas and buckwheat. These differences will continue to grow during the observation at the end of August where mustard was very short and had almost set seed.
Weighing analysis and trapped Nitrogen estimates
For this step, it was weighing of the aerial parts at the end of August that was used as a combined method to give an evaluation of response. So logically, we are witnessing an important difference between the techniques, which verifies the field observations. For mustard If the biomass is almost similar between the ‘cultivated’ part and “rolled stubble” it doubles for the ‘High stubble’ as the picture shows, which is confirmed by weighing. This difference is logically in trapped nitrogen with rather large gaps despite levels of weak plants. This shows, like the behaviour of the plants from earlier, that post-harvest nitrogen residues were very low in this plot, a low level certainly maintained throughout the dry summer.
For peas
For this legume, the initial difference is maintained and even amplified in time with the ‘high stubble’ area which stands out as having double the biomass in late summer. This experiment once again demonstrates that legumes appreciate a little free nitrogen or fertility at sowing and during their emergence . So that once in place, they can start to compensate by symbiotic fixation. So if we compare nitrogen contained in the mustard and in the peas, the arithmetic is almost right.
The bacterial symbiosis allowed them to double what has been taken from the ground but no more. However, this is where the peas are the most vigorous at establishment, and certainly better fed early, and that the total amount fixed is the most important (about 35 kg in the ‘high stubble’ against 15 kg in cultivated stubble).
So for legumes, the quality of the establishment does not only influence the biomass but also their capacity to return free nitrogen into the system. Also differences are to be expected for the buckwheat. However this can achieve, in the ‘high stubble’ situation”, the highest biomass with 2.6 t of MS in slightly more than 45 days. This level of production confirms its speed of growth in summer and even in dry conditions, which in makes it a very competitive plant against a lot of summer dicots. It also confirms here its aptitude as a second harvest option.
The amount of trapped nitrogen is pretty intriguing then, as this plant is not a legume that can fix nitrogen, nor a cruciferous plant considered very nitrogen hungry. Buckwheat demonstrates however here it can be very powerful and that it is capable of scavenging or even draining the soil of its fertility more than other classic cover crops. It is certainly, and partly for this reason, that buckwheat has the reputation of keeping fields clean. As its common name of “Black wheat” could lead one to think, it is simply nitrogen hungry and it is this which allows it to dominate. It is logically for that reason that the grains that follow it need a small fertilizer application, especially in direct seeding.
Points to remember and explanation hypotheses
This experiment and especially the weather conditions following sowing showed very clearly all the issues and differences involved in the sowing and establishment of covers in summer:
• The higher the stubble is left, the less they disturb the seedling quality, especially with a disc seeder. This potentially gives rise to the use of the Shelbourne stripper header in zero-till situations.
• High stubble is shading and especially limits the velocity of the wind at ground level which is one the biggest factors causing moisture loss by evaporation. In summer, warmth of the surface is certainly less important than moisture retention under a layer of rolled straw.
• A high stubble benefited more from light rain as was the case this summer (8 mm). A good mulch limits evaporation, but it is necessary to count at least a good ten mm of rain to cross this barrier which works like a blotter for a really wet soil. When the humidity is low, as often in summer in covers, it is necessary to limit all sources of waste and these are ultimately all these little amounts of water that end up making a big difference in establishment and growth.
Finally, it is impossible to forget in this debate the influence of early fertility and nitrogen. The presence of straw on the ground, even in the form of mulch, will take a part of the fertility available in the first inch, the area where the seedlings need to settle in and germinate. The situation is even worse in the mulched area: even if the low tillage triggered a slight quicker germination it was slowed down by the dry conditions, and the volume of straw incorporated has constantly demanded the available nitrogen to the detriment of the covers. This is an only too classic phenomenon.
For more information on Nitrogen management in intercropping read also: “How much nitrogen may be required for the decomposition of straws? “ For successful covers, it is not enough just to have the right drill and concoct the best mixtures; it is necessary to learn everything about managing the straw during the harvest according to the operating conditions. It is also necessary to remember that poor fertility at the time of sowing is always detrimental even for covers that suffer more often from a lack of nitrogen before lack of water, while many think the opposite to be true.
You can read the Article online which is on Page 12 of Direct Driller Magazine here: https://issuu.com/directdriller/docs/direct_driller_issue_2/12
Written by Frederic Thomas, TCS Magazine n°95. November/December 2017
The experiments and measurements that follow were carried out by Étienne Mignot (engineering student) on the farm of David Guy in Loire-Atlantique (sky France).
In order to observe the quality of emergence and the development of machinery, a variety of plants were sown with a (EasyDrill) disk drill as soon as the harvest was completed (July 10, 2017) with 3 modes of management of crop residues: high stubble (cutting at 40 cm), short straw rolled (8 cm) and rolled short straw followed by shallow stubble cultivation (5 cm deep).
The crops observed are mustard, peas and buckwheat, which serve as indicators; the other plants, according to their typology, had quite similar reactions and developments. These 3 species were used for these reasons - Mustard is often the most common “minimum cover” because it is cheap with the guarantee of good establishment; Feed pea is a legume which fixes nitrogen and it is logically a cover that must, in fact, be less sensitive to possible problems in summer after harvest. (NB In France of course !) Buckwheat was chosen as a cover that emerges quickly in summer but also as it is a commonly used species in catch cropping. In addition in 2017, spring and summer were extremely dry in the Loire Atlantique: 9 mm between sowing and first emergence, only 8 mm in the first half of August and 21 mm at the end of the month.
The dynamics of emergence
These particular conditions, which correspond more to what the majority of farmers may normally encounter in the area, have certainly amplified the differences and have highlighted the pitfalls in terms of summer cover establishment. Not surprisingly (see Figure 1), it is in the ‘rolled straw’ that the emergence is lowest, all species combined, while the ‘high stubble’ is similar. This observation confirms the difficulty of cutting through a “mattress” of dry crop residue just after harvest. The ‘hairpinning’ of the straw in the furrow is not a fable but a reality.
Stubble rolled is shown to be the worst option. On the other hand, conservation stubble cut high shows an interesting solution to protect seedlings at this time and in these conditions. As the flea beetles attacked very early in cruciferous crops this summer, the straw height seems to have disturbed them (Figure 2). Indeed, only 25% mustard seedlings were affected in the high stubble while 68% were attacked with rolled stubble and 85% in the cultivated version. This is a comforting observation on the effect of companion plants in rapeseed: from the moment they cover and even hide the seedling, some pests are avoided. It also confirms that healthy rape seedlings that grow quickly are a lot less affected.
Above Left: Mustard August 28th : except for height differences that remain important (36 cm high stubble, 28 cm in short stubble and 31 cm in the cultivated area), this observation shows up a strong difference in growth stage. The ‘high stubble’ has a bigger leaf surface area and a much larger biomass than the other two and has very few flowers. This difference in appearance confirms that in the ‘high stubble’ the plant has developed well in better conditions and with less stress, particularly related to nitrogen, as opposed to the others. Above centre and right: Peas and Buckwheat on August 28th: As shown in this picture taken on August 28, even peas, (legumes) are affected by the stubble height. in the ‘high stubble’, they have about 86 leaves on average with a lot of tendrils against 54 for the shorter stubble and 48 for peas in the cultivated area. It’s as if the difference achieved at sowing and emergence had continued to grow. The vegetation gap is equally impressive with the buckwheat that has reached the flowering stage.
Early developments A first observation, 3 weeks after sowing, the differences in techniques are already apparent. The establishment is generally better in the high cut stubble, then that seedlings are much weaker in straws rolled with or without stubble cultivation. The difference is more obvious with the peas. The ‘High stubble’ already shows thirty or so shoots with the appearance of the first tendrils, while in the shorter stubble the number of leaves goes down to 24 and even fall to 20 in the rolled straw.
A beautiful demonstration which confirms that the peas enjoy the companion crop, giving protection but also supports on which they can grab early. The difference in height of the cover also makes a big difference for buckwheat in favour of stubble cut at 40 cm. Measurements made 2 weeks later in the middle of August reinforce these first observations with big differences especially for peas and buckwheat. These differences will continue to grow during the observation at the end of August where mustard was very short and had almost set seed.
Weighing analysis and trapped Nitrogen estimates
For this step, it was weighing of the aerial parts at the end of August that was used as a combined method to give an evaluation of response. So logically, we are witnessing an important difference between the techniques, which verifies the field observations. For mustard If the biomass is almost similar between the ‘cultivated’ part and “rolled stubble” it doubles for the ‘High stubble’ as the picture shows, which is confirmed by weighing. This difference is logically in trapped nitrogen with rather large gaps despite levels of weak plants. This shows, like the behaviour of the plants from earlier, that post-harvest nitrogen residues were very low in this plot, a low level certainly maintained throughout the dry summer.
For peas
For this legume, the initial difference is maintained and even amplified in time with the ‘high stubble’ area which stands out as having double the biomass in late summer. This experiment once again demonstrates that legumes appreciate a little free nitrogen or fertility at sowing and during their emergence . So that once in place, they can start to compensate by symbiotic fixation. So if we compare nitrogen contained in the mustard and in the peas, the arithmetic is almost right.
The bacterial symbiosis allowed them to double what has been taken from the ground but no more. However, this is where the peas are the most vigorous at establishment, and certainly better fed early, and that the total amount fixed is the most important (about 35 kg in the ‘high stubble’ against 15 kg in cultivated stubble).
So for legumes, the quality of the establishment does not only influence the biomass but also their capacity to return free nitrogen into the system. Also differences are to be expected for the buckwheat. However this can achieve, in the ‘high stubble’ situation”, the highest biomass with 2.6 t of MS in slightly more than 45 days. This level of production confirms its speed of growth in summer and even in dry conditions, which in makes it a very competitive plant against a lot of summer dicots. It also confirms here its aptitude as a second harvest option.
The amount of trapped nitrogen is pretty intriguing then, as this plant is not a legume that can fix nitrogen, nor a cruciferous plant considered very nitrogen hungry. Buckwheat demonstrates however here it can be very powerful and that it is capable of scavenging or even draining the soil of its fertility more than other classic cover crops. It is certainly, and partly for this reason, that buckwheat has the reputation of keeping fields clean. As its common name of “Black wheat” could lead one to think, it is simply nitrogen hungry and it is this which allows it to dominate. It is logically for that reason that the grains that follow it need a small fertilizer application, especially in direct seeding.
Points to remember and explanation hypotheses
This experiment and especially the weather conditions following sowing showed very clearly all the issues and differences involved in the sowing and establishment of covers in summer:
• The higher the stubble is left, the less they disturb the seedling quality, especially with a disc seeder. This potentially gives rise to the use of the Shelbourne stripper header in zero-till situations.
• High stubble is shading and especially limits the velocity of the wind at ground level which is one the biggest factors causing moisture loss by evaporation. In summer, warmth of the surface is certainly less important than moisture retention under a layer of rolled straw.
• A high stubble benefited more from light rain as was the case this summer (8 mm). A good mulch limits evaporation, but it is necessary to count at least a good ten mm of rain to cross this barrier which works like a blotter for a really wet soil. When the humidity is low, as often in summer in covers, it is necessary to limit all sources of waste and these are ultimately all these little amounts of water that end up making a big difference in establishment and growth.
Finally, it is impossible to forget in this debate the influence of early fertility and nitrogen. The presence of straw on the ground, even in the form of mulch, will take a part of the fertility available in the first inch, the area where the seedlings need to settle in and germinate. The situation is even worse in the mulched area: even if the low tillage triggered a slight quicker germination it was slowed down by the dry conditions, and the volume of straw incorporated has constantly demanded the available nitrogen to the detriment of the covers. This is an only too classic phenomenon.
For more information on Nitrogen management in intercropping read also: “How much nitrogen may be required for the decomposition of straws? “ For successful covers, it is not enough just to have the right drill and concoct the best mixtures; it is necessary to learn everything about managing the straw during the harvest according to the operating conditions. It is also necessary to remember that poor fertility at the time of sowing is always detrimental even for covers that suffer more often from a lack of nitrogen before lack of water, while many think the opposite to be true.
You can read the Article online which is on Page 12 of Direct Driller Magazine here: https://issuu.com/directdriller/docs/direct_driller_issue_2/12