Today we explore some benefits of including sunflowers in your crop rotation cycle especially when growing wheat. I have discussed the benefits of Sunflowers in the rotation in previous editions of #ThinkAgronomy, in reducing nematode populations, building Mycorrhizal fungi and improving soil structure. The challenge on the flip side is making them pay in their own right to contribute some cash to the operation as well as improving the profitability of the other crops. Well here are two examples that I have seen in the last week where they have been used as a double crop, in the off season, with – largely – positive results.
sunflower crop rotation
Wheat after double cropped Sunflowers on the left (where they used all the moisture in what would have been a fallow), and after a true fallow on the right where the moisture was preserved, but there is a lot more Brome.
This was an exceptional example where the farm only received 220mm of  rain since August, but in a dryland environment it shows how one should be cautious about double cropping. Yet the Brome control is massively improved and early on in the crop there just wasn’t the germination that occurred in the wheat after the fallow (the fallow was spotless with no weeds allowed to get past 4-5 leaf stage). So there is clearly something happening here with Sunflowers, either an allelopathic effect, suppression from the extra residue around the wheat or perhaps the action of planting sunflowers has encouraged the Brome to germinate which we then controlled with a graminicide.
Sunflower farming
Brome Grass giving up under the shading effect of a very dense canopy. Most of the flush was controlled with a graminicide until the crop became too tall to spray.
This is another very useful effect of the crop against Brome, and for drier areas you do not need to follow the crop through to harvest to benefit – our agronomist George Maweu was explaining how in Narok they used to let the Sunflowers get up above the weeds towards heading stage, then spray it off. This is long enough to provide good soil cover, significantly reduce the number of glyphosate passes in the fallow, produce some deep roots and plenty of surface residue without it being too difficult to plant through. Planting multi species is the next step to further improve fertility and soil biology, but this vies the flexibility to take it through to a full crop if  conditions look promising, or treat it as a cover crop if moisture is looking short in the soil profile. Just remember the golden rule of cover cropping; 60-70 days is about the max before the crop starts really using moisture that may detriment the following crop.
Center of Excellence for Crop Rotation Agventures
Farming for the future requires a change of approach. Monoculture, soil degradation and climate change and soil degradation are threats to the future
of how we feed the planet. Agventure Ltd set up the Center of Excellence for Crop Rotation to help farmers diversify cropping systems and introduce techniques which have a long-term outlook to improve soil health. The Center of Excellence for Crop Rotation works extensively with Crop Nutrition Laboratory Services Ltd (CropNuts). Till next time, Happy farming, David,
David Jones

About David

David Jones is the Broad Acre Specialist at Crop Nutrition Laboratory Services Ltd. (CROPNUTS). David has a keen interest in soils and no till farming systems where he has undertaken work looking into weed levels and changes in soil structure, and has extensive experience in field trials and in the development of precision farming techniques. In his spare time he enjoys playing rugby.