C4 cover crops

Charles Quick

Member
Mixed Farmer
Location
Somerset
Probably mad to think this, but...

Are C4 plants a good choice for summer established cover crops?
Not necessarily maize, thinking more along the lines of millet/sorghum which would work better in a small seed mix.

Very water efficient so should be able to get established in late July after OSR, then put on plenty of biomass before termination in October for WW. May be less suited for an August - March cover behind wheat, but if it gives up and breaks down earlier it could leave a more open cover (say, just Phacelia, clover and volunteer cereals left) for better drilling/establishment.

It's also unrelated to all crops in the rotation, reducing reliance on cereal-type crops to provide the bulk of the biomass. Maybe a slightly increased risk of Fusarium but as it will never get to seed I doubt it's a real issue.

So, does anyone know where I could find a tonne of feed-quality grain to try?
Or can you tell me where I've lost the plot?
 

Jimbo26

New Member
Interesting thought @Charles Quick. Do you plan on grazing this cover or letting it over winter? It should get up and away before winter, putting on some good biomass. Maybe mixing it with a C3 cover would keep the cover green over winter. The main thing is the c4 residue will protect the soil. Have you tried this? If so how is it going?
 

Charles Quick

Member
Mixed Farmer
Location
Somerset
I bought a tonne of birdseed red sorghum for £400. I was feeling generous and wanted to feed the crows on my covers.... Unfortunately some of the bloody stuff grew didn't it!
It's a bit pathetic this year, drilled around 10th August. It all germinated quickly but sat at two/three leaves for a month, until the last few weeks when it's started pushing on again, but it's still less than 10cm tall and is quickly getting outcompeted. Maybe because it was probably F2 hybrid seed, but it could also be the conditions this summer. I have also read that those are the symptoms of 'long fallow disorder', caused by a lack of mycorrhizal association, but considering this is year 21 of no-till here I doubt our soils lack AMF.
I didn't get any in time to go after the OSR, which was where I had hoped to put it, so that's next year's experiment and hopefully it'll grow faster if drilled in July.
The slugs hate it, the young and stressed leaves are very bitter and contain cyanide, however I have read that lush growth is quite grazeable.
 
I bought a tonne of birdseed red sorghum for £400. I was feeling generous and wanted to feed the crows on my covers.... Unfortunately some of the bloody stuff grew didn't it!
It's a bit pathetic this year, drilled around 10th August. It all germinated quickly but sat at two/three leaves for a month, until the last few weeks when it's started pushing on again, but it's still less than 10cm tall and is quickly getting outcompeted. Maybe because it was probably F2 hybrid seed, but it could also be the conditions this summer. I have also read that those are the symptoms of 'long fallow disorder', caused by a lack of mycorrhizal association, but considering this is year 21 of no-till here I doubt our soils lack AMF.
I didn't get any in time to go after the OSR, which was where I had hoped to put it, so that's next year's experiment and hopefully it'll grow faster if drilled in July.
The slugs hate it, the young and stressed leaves are very bitter and contain cyanide, however I have read that lush growth is quite grazeable.
we grow a lot of sorghum in this part of the world, both forage & grain varieties

yes, grain sorghum can contain cyanide ( prussic acid ) & high nitrate levels, which can be toxic to stock, but generally only if the plant is severely moisture or heat stressed.
very common here to graze cattle on grain sorghum regrowth after grain harvest.
My grain sorghum I planted this summer ( November ) was severely heat & moisture stressed this year, to an extent that it produced no grain ( first time ever for me. The heads were "cooked in the boot", which means they were literally steamed to death & rendered infertile by extreme heat, while still in the stem ). Anyway, tested it for nitrates & prussic acid, levels were high. A neighbour was short of feed & ended up running 80 cows & calves on one block for 4 months with no issues

if you want sorghum to grow quickly, you need enough moisture & warmth - think northern NSW - southern Qld warmth. We plant in spring, it grows through summer & we harvest in autumn

Sorghum after canola ( OSR ) is considered less than ideal here. Sorghum benefits from high VAM levels & we find canola doesn't support / tends to reduce VAM . . .
 

CornishTone

Member
Location
Cornwall
I bought a tonne of birdseed red sorghum for £400. I was feeling generous and wanted to feed the crows on my covers.... Unfortunately some of the bloody stuff grew didn't it!
It's a bit pathetic this year, drilled around 10th August. It all germinated quickly but sat at two/three leaves for a month, until the last few weeks when it's started pushing on again, but it's still less than 10cm tall and is quickly getting outcompeted. Maybe because it was probably F2 hybrid seed, but it could also be the conditions this summer. I have also read that those are the symptoms of 'long fallow disorder', caused by a lack of mycorrhizal association, but considering this is year 21 of no-till here I doubt our soils lack AMF.
I didn't get any in time to go after the OSR, which was where I had hoped to put it, so that's next year's experiment and hopefully it'll grow faster if drilled in July.
The slugs hate it, the young and stressed leaves are very bitter and contain cyanide, however I have read that lush growth is quite grazeable.
@Agrispeed tried millet and sorghum as part of a cheap birdseed mix and seemed to have good results when sown early June I think.
 

PuG

Member
@Agrispeed tried millet and sorghum as part of a cheap birdseed mix and seemed to have good results when sown early June I think.
Sorghum needs warm soil temperatures, long hot sunny days, doesn't like being in the shade at all. Mine took about three weeks to come up and a good month hovering about 12", then accelerated, done three cuts 4 - 6ft high average. The silage which I'm feeding now from earlier in the year is beautiful. Just terminating it now for over winter cover. Be careful grazing, wait until its a decent height from the prussic acid point of a view and if your not sure cut it for hay or silage and feed it back to them. Farmer near here lost five cows to it a few years back by escaping into a field with allot of fresh growth.

Next year im doing Pearl Millet, Sorghum x Sudan hybrid (which I did this year, and compared to a local Pipper preformed much better and fleshy growth) and im going to try a Sorghum Forage mono cut some like 140 day maturity? one field of Sorghum grain but suits our land and climate. I'm only just starting to experiment, thats a few on the forums who knows heck of a allot more about it. (Farmer Roy!)

Cut last week

WhatsApp Image 2019-10-03 at 22.25.49.jpeg
 
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What are your max / min temperatures & also soil temp at 9.00am?

sorghum likes a fair bit of heat

we plant it in our spring, so it is growing through our summer & grain crops harvested in autumn . . .

The pics below are of a failed grain sorghum crop I planted in November last year. Dunno how much you know about our current weather, but due to extreme heat & lack of moisture it didn’t produce any grain. We cut it in June for hay, to retrieve something out of it. No rain since then, with no subsoil moisture. We’ve already had temps well up into the mid - high 30’s C even though it’s early spring. This is the plants 3rd attempt since then of having another crack at life ( the other 2 times were burnt off by frost / cold weather )
It is happiest in temps from say mid 20’s - low 30’s C
I don’t know if you would have enough heat units for it to reach its full potential ?

we don’t plant it till soil temp at 9.00am is 12 C & rising . . .

8503AF2E-23B8-45C0-AB4F-4C57BE968BEA.jpeg
8589A681-DCE2-4DDA-A54B-0EACA4D5CA46.jpeg
8503AF2E-23B8-45C0-AB4F-4C57BE968BEA.jpeg

sorry for the lack of ground cover. We are fully zero till & that sorghum was planted into standing wheat straw, but it has long since decomposed, oxidised or just physically broken down since then . . .
 
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Charles Quick

Member
Mixed Farmer
Location
Somerset
I was never expecting it to reach full potential, just to be a reasonable plant more than a few inches high. Like you say it's probably just too cold!
Air temps vary between 8 and 15c, soil is still warm to the touch but the rain has taken a lot out of it - say 10c.
 
I was never expecting it to reach full potential, just to be a reasonable plant more than a few inches high. Like you say it's probably just too cold!
Air temps vary between 8 and 15c, soil is still warm to the touch but the rain has taken a lot out of it - say 10c.
Ok
Yeah - too cold
At 10 C soil temp you won’t get much growth & it will be weak & spindly

as an indication, sorghum generally requires more heat than maize
It is our main warm season grain crop & thrives in conditions that are too hot or dry for maize to reliably grow
 
Sorghum looking quite sick. Must be the cold/wet/lack of N in solution? The rest of the cover is happy
It's a warm weather crop. Will look pished off by now in Somerset given the weather we have just had.

Only ever seen sorghum drilled in June. In most years May will not be reliably warm enough to get it to germinate and grow strongly. Hates competition from other species.

I am not sure I would see the advantage in drilling a C4 plant as a cover. Fast growth in summer yes but over winter they won't be at all happy.
 

Charles Quick

Member
Mixed Farmer
Location
Somerset
Quite, perhaps I should've written catch crop.
I was planning to slot it in as part of a catch crop between OSR and wheat, so July drilled and September terminated, however the seed came too late so I put it in the winter cover regardless
It was a cheap experiment, going to try again with the remainder of the seed next summer after OSR, If it doesn't grow in the tropic of Somerset it won't have much chance elsewhere in the UK!
 
Quite, perhaps I should've written catch crop.
I was planning to slot it in as part of a catch crop between OSR and wheat, so July drilled and September terminated, however the seed came too late so I put it in the winter cover regardless
It was a cheap experiment, going to try again with the remainder of the seed next summer after OSR, If it doesn't grow in the tropic of Somerset it won't have much chance elsewhere in the UK!
just be aware, we would normally avoid planting sorghum after OSR / Canola, as canola doesn’t support AMF / VAM fungi . . .
Sorghum can struggle after canola because of this . . .
 

PuG

Member
Once its established it tends to overwhelm other crops, under sown mine with clover. Even here it wasn't the most vigorous to begin with. The mistake I've made, given I need the fodder I took the last cut rather than broadcasting and letting it go down over my winter cover crop - did some light tillage to use conventional drill and now watching my field wash off down the road with the torrential rain walloping us.
 

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