Helping backward winter wheat crops after a wet start31 January 2024
After one of the wettest winters on record, some arable crops will need extra attention to see them through to a productive harvest, with bespoke nutrition planning, robust disease control and a suitable weed strategy essential to maximise yields.
Wet weather in October and December prevented large areas of winter wheat from being drilled last year, with many of those that were planted subsequently sitting in water-logged soils which hampered establishment and early season development.
November’s brief spell of drier weather enabled some remaining crops to be drilled, albeit in less-than-ideal conditions which contributed to sub-optimal establishment. December’s wet weather added to the pressure on struggling crops, causing them to fall further behind.
As a result, growers now face the tricky predicament of deciding how to reinvigorate crops, and, in the worst cases, to decide if, and when, to write off the worst crops and start again.
“For some growers the 2023-24 season could go down as one of the trickiest in recent memory,” explains Mike Thornton of agronomy firm, ProCam. “It’s not all gloom though, with those crops which were drilled before the wet weather arrived getting away well and, in some instances, looking very advanced.
“The wet conditions enabled residual herbicides to work well on earlier drilled crops and have provided a strong start to weed control. But they have also given rise to plenty of disease pressure, especially from septoria,” Mr Thornton adds. “A robust fungicide programme will therefore be essential, but growers should be aware that excessive tank mixes could have the potential to harm the crop if the spring is wet also.”
For crops which didn’t receive any herbicide treatment before the wet weather took hold, weed pressure will be more serious, Mr Thornton explains. “In the worst cases, for example where a crop with a low plant population is full of blackgrass or ryegrass, the only option might be to write the crop off and start again. But that decision shouldn’t be taken in haste, especially if the grassweeds are still small and sensitive enough that a residual or contact herbicide in spring will still provide effective control.”
Beyond weed control, growers will also need to think hard about how to feed struggling crops, especially as the wet conditions will have caused soil residual nitrogen reserves to be depleted. Growers will therefore need to amend spring nutrient plans accordingly, although Mr Thornton warns against applying too much too soon.
“Our estimation is that soils could be carrying 40-60kg/ha less nitrogen than usual due to leaching,” he declares.
“That will need to be replaced, but there’s little point throwing too much fertiliser at crops that don’t look fantastic, especially if conditions turn really wet again. It’s really a matter of looking at each field individually when deciding how, where and when to feed crops.”
In a year as tricky as this, Mr Thornton encourages the use of soil sampling to understand each field’s nutrient status, and, where possible, to vary application rates accordingly. However, do not only test for the levels of nutrients in the soil, he stresses, use a test that also indicates the levels actually available to the plant.
“Marginal crops of wheat and hybrid barley will still have the potential to recover if they receive an early application of nitrogen, but only if enough plants have established. For wheat that means 80-100 plant per m2.
“One strategy might be to apply a reduced dose (30-40kg N/ha) as early as possible in February and to continue on a little-and-often basis throughout the spring to encourage tillering.
“However, if the first application is delayed until March, a heavier rate of up to 80kg N/ha will be more appropriate, conditions permitting. Adding sulphur at the same time will maximise the efficacy of N.”
Mr Thornton also warns that the wet winter conditions could have hampered rooting. “Don’t be deceived by crops that look healthy above ground as the wet conditions will have done little to encourage root development,” he explains. “If conditions turn and stay dry, those crops which haven’t put down a decent root could soon start to suffer. Use a biostimulant or phosphite based treatment at T0 to encourage better root development,” he suggests.