The wet autumn and winter have presented serious difficulties for crops in the ground, as well as those still to be drilled.
Neil Watson, technical manager at Hutchinsons, explained that while some early sown crops looked good but others have been hit hard. Crucially, when soils are waterlogged roots are starved of oxygen, preventing the movement of water and nutrients to the top growth.
“Ironically, the stomata close, almost like in drought conditions, which affects photosynthesis, with knock-on effects for nutrient uptake, tillering and biomass accumulation.
“In a normal situation, tiller production might be around 1,200/m2, producing 500-600 ears/m2, but in extremely wet conditions, particularly when waterlogging occurs close to emergence, tillering may be nearer half that.”
In severe cases, crops can also cannibalise nutrients from older leaves to support new growth, causing early senescence. In wet conditions, the roots will also adapt by growing closer to the surface for gas exchange in anaerobic soils. This presents issues as the season progresses through, especially if conditions become dry and the crops need to scavenge for water and nutrients.
“Without the foundations, you haven’t got the critical structure to build growth throughout the season.”
Hutchinsons recommends assessing the soil and crop condition in individual fields and identifying issues and crop requirements. This will lead to some tough questions about the viability of certain crops, or areas within the field and whether re-drilling or replacing the crop with a cover crop, is necessary.
Early nutrition for root development and biomass is crucial, with nitrogen being one of the most important considerations, explained fertiliser manager Tim Kerr.
“The first N-Min results for this year show there is less residual nitrogen in the soil than we’d normally see, primarily as a consequence of nitrate leaching. But it’s a quadruple whammy; there’s less nitrogen in the soil, less in the crop, poorer rooting, and reduced mineralisation due to the impact of waterlogging on soil microbes. We’re facing a very different scenario to previous years.”
Sulphur is also important, as sulphates can leech much like nitrate. “Ideally, apply sulphur with the first nitrogen, or alongside the potash. Rates should generally be in proportion to the amount of nitrogen applied.”
Samples have shown that more than 70% are low in boron, especially those on lighter land. Tim added: “Deficiency symptoms are rarely seen, but boron plays a vital role in root and shoot development. Trials in 2020 showed a positive response from foliar boron applied at GS 30 and GS 39.”
Growers should also consider potassium and magnesium, which can be lost from lighter soils that have a low cation exchange capacity. Phosphate availability could also be lower, due to soil runoff in heavy rain.
“In cold, wet soils, the microbes that convert exchangeable P to available P slow down, so crops can quickly exhaust the soil solution, resulting in deficiency symptoms, even where soil indices are high,” Tim said.
“Foliar products are an option if there is sufficient leaf area, however phosphites may be a more effective option to develop rooting and improve future scavenging ability.”
The timely application of plant growth regulators (PGR) could also play an important role in manipulating crops to offset the damage done by waterlogging, according to regional technical support manager Alice Cannon.
“[These] are not just about straw shortening; the chemistry can manipulate crops in many other ways, depending on the product choice, rates and timing.”
Trials held last year showed that early PGR applications at T0 (GS 30-31) and T1 (GS 32) can improve stem diameter and width, boosting resilience against lodging, which will be particularly important in shallow-rooted crops.
The same trial found that tiller survival can benefit from PGRs. “Tillers will abort from stem extension, and that’s simply not an option this year given we’re already facing a reduction in tillering due to the compromised foundation period. The potential for fertile tillers is determined by the number of leaves present at stem extension, so keeping green area index going through March is crucial to building yield.”
However, Alice cautioned that care would be needed when choosing product and application rates, with slightly higher rates on more forward early-sown crops. “Growth stage 30 will be an extremely important timing this season. It’s traditionally a disease control timing, but it’s just as important to manipulate crops at this stage to maximise their potential.”
Indications show that certain diseases are likely to be a greater risk this season due to the prolonged wet weather and milder temperatures. David Howard, head of integrated crop management, advised that close monitoring and early action will be vital.
Septoria development is present in early-sown wheat, thanks to the favourable conditions, although eyespot could prove to be more problematic due to the wet autumn and low varietal resistance.
Wet soils may also increase spread, and mildew is likely to be a risk for stressed crops, perhaps more so in barley. Where there is the risk of rain splash, net blotch and rynchosporium are also likely to be present.
Later drilling can increase the rust risk and there has been a lack of hard frosts to kill inoculum this winter.
“Ironically, we might see some benefit where flooding has taken away the lower leaves that can carry rust or Septoria spores over winter, but that will be balanced against the damage flooding’s done to crop stress and development.”
However, early action at T0 and T1 will be crucial with fungicide choices tailored to the needs of individual fields. Trials have shown some good results from elicitors at GS 30, which can increase energy uptake in stressed crops and support natural disease protection.
Products that mimic the natural defence mechanisms may also be worth considering for Septoria and mildew, but more as a preventative measure in healthier crops.
Timing could be the biggest issue. David said that sprays should be timed on the parts of the field with the highest yield potential. “Don’t wait for poor areas to catch up and risk letting disease into the good parts.”
While he also recognised the need to get early nitrogen on backwards crops, large doses could cause excess nitrogen in the leaf which can increase disease pressure. “A split dose approach may be more effective, both for efficient crop uptake and for minimising disease risk.”
For more advice, go to www.hlhltd.co.uk