Four things to consider in post-harvest cultivations for establishing a winter crop – Arable Farming – Dick Neale
The last season has really highlighted where soil health can be improved, particularly when coping with both too much and too little water ...
Soil expert Dick Neale offered his top tips on soil management ahead of the drill during a webinar organised by Hutchinsons.
1. Identify the issue...
“The first thing to do is identify your issue,” Mr Neale said. “What is the current crop telling you? If it is level, evenly green and has responded well to the rain, there are few immediate issues within the soil, particularly in spring crops like beans or maize which will highlight any issues within the soil.
“Compare cereals in neighbouring fields where late harvested crops were loaded on headlands versus in the field. It is easy to assume that every late, wet harvest is causing damage lower in the soil, but it is not always the case.”
It is also important to check both bare and cropped fields after a decent rain to see how soil copes with water infiltration and to review its structural condition compared to when its dry, he said.
2. Dry soil is not necessarily compacted soil...
Ninety per cent of soil water management issues this past season are focussed in the top 100-125mm of soil, not the lower profile like many first think, said Mr Neale.
“Poor water movement from the surface is often assumed to be poor drainage, but inspections are highlighting water infiltration at the surface is the key reason for ponding, capping and crop failure.
“Subsoiling will not address this unless you set it very carefully to shallowly move the soil in the right way,” he said.
“An early harvest might see mole draining coming to the fore, but it is pointless going 24 inches deep to remove water from a field if the issue is 4 inches deep in the soil.”
Issues with poor infiltration of water into the surface of soil, rather than drainage out the bottom is the major issue for a lot of soils, in part due to an increase in reduced tillage influenced by the need to control black-grass, reduce costs and manage larger areas.
“There still remains a desire to move soil straight after the combine as if we are bringing up big lumps of clay that needs to be weathered for eight weeks back into a seedbed. If we have moved to shallow tillage, we are not creating that coarse seedbed initially that needs all that weathering. So, we should try and stop ourselves getting in there too early.
“Short disc machines are increasingly being used. The problem is these produce a fine aggregate seedbed from day one. If it is slightly damp in clay, they will smear the bottom of the cultivation. This can lead to a lot of capping and poor infiltration.”
Late drilling is still required for grass-weed control, but growers should bear in mind that heavy rain is more likely in late October, said Mr Neale.
“Fine silt and clay aggregates collapse and block surface fissures. Water is held up on the smeared base of the seedbed and causes seed to rot.
“Keeping soil covered in crop residue will protect it from the weather and make drilling easier later on because you are not just drilling into wet sticky soil,” he advised.
For direct drillers faced with chaff lines behind the combine or poor soil contact in the seedbed compromising crop establishment, Mr Neale said they should not feel like they are failing by doing a very light cultivate ahead of the drill.
“Surface residue can be a blessing or a hinderance in equal measure, depending on its carbon:nitrogen ratio and how it is managed.”
4. Aggregation is a natural process...
Growers should also focus on building soil structure. Seeing soil blowing off the field is far from natural, and it is indicating how unstable the aggregate structure of the soil really is, Mr Neale said.
“When it rains like last autumn, those individual sand and silt grains then block the surface pores of the soil and will not let water infiltrate – then we get ponding. Water is held up on the smeared base of the seedbed and poor crop establishment results.
“Aggregate structure is built naturally over time, but cultivations destroy aggregate structure. If you put a subsoiler in to remove an identified area of compaction, you are removing the compaction, not restructuring the soil.”
One of the best ways to establish good natural aggregation in soil is to have a good crop with strong roots growing, Mr Neale said.
“Roots, both growing and remaining in the soil are key to soil stability, porosity and building organic matter. Multiple species is where you have to be with cover crops.
“Do not forget worms either –they are a vital component for aggregate creation.