Increasing plant vigour will be key to getting the best out of stressed crops this spring, says Agrovista agronomist Craig Green
Some key plant nutrients are likely to be in short supply this spring after one of the wettest winters on record.
Many autumn-sown crops look pale and stressed after prolonged rainfall moved key elements down the soil profile. These crops also have smaller root volumes, making matters worse, says Mr Green. Spring crops are also at risk unless following cover crops, which have done an excellent job in capturing nutrients this winter. Even in the drier east, leaf tissue samples of both winter cereals and oilseed rape submitted last month flagged up widespread potassium deficiency, with boron, manganese, magnesium, sulphur, zinc and copper also in short supply in many fields.
To help alleviate or prevent stress Mr Green recommends Terra-Sorb, an amino-acid based biostimulant that helps plants recover from stress by boosting nutrient uptake, photosynthetic activity and root and shoot growth.
“It can be used in any situation to increase vigour and plant development in spring – I describe it as Red Bull for crops,” says Craig.
“It can be applied any time a crop needs a pick-me-up. It is compatible with fungicides so in winter cereals we tend to use it at the end of tillering at 1.5-2 litres/ha so plants are in good shape before entering stem extension.”
However, he recommends it most frequently in spring crops, particularly sugar beet and maize.
“Two years of trials in the UK have shown significant potential to increase yield and sugar content in beet, especially on lighter soils and sands that are prone to drought,” he notes.
“The aim should be to apply it when the crop has 2–4 leaves at 0.3 litres/ha, tank-mixed with a post-emergence herbicide. Plants are more vigorous and put down bigger roots and are better able to grow away and withstand stress.”
Independent (CMi) trials have shown 2 litres/ha of Terrasorb increased sugar content by 0.43% as a single dose at the four-leaf stage, and yield by 1.42t/ha, says Craig. He also uses it on maize crops for biogas to promote root and cob development. “Maize is a C4 plant so cool May temperatures can slow growth and cause yellowing as roots struggle to develop and access nutrients, particularly phosphate. This is particularly the case with maize grown in arable rotations which haven’t received FYM,” he explains. “Terra-Sorb can also be used with fungicides, so can be applied later on to provide the crop with extra energy three to four weeks ahead of tassling to extend the cobbing period.”
Keeping nitrogen where it’s needed
Maintaining sufficient nitrogen in the top few inches of the soil early on is critical for optimum crop performance, says Mr Green. Wet weather after early N applications won’t have helped efforts to restore soils depleted by the winter deluge.
“Most nitrogen is generally applied to winter crops in the early stages of crop development – for example, about 75% goes onto wheat by GS 32. Spring crops such as maize often receive all of it in the seed-bed.
“We need to ensure there is enough for plants to make optimum use of it when they start building yield, particularly on light soils prone to leaching, soils prone to waterlogging or cold soils where N has been applied early.”
In these cases Mr Green recommends N-Lock, a nitrogen stabiliser that slows the bacterial conversion of ammonium(bagged N) to nitrite for up to six weeks.
“Ammonium is positively charged, so is attracted to negatively charged soil particles so it can’t be leached from the rooting zone after heavy rain,” he explains. “Nitrate is negatively charged so is more prone to leaching.”
Winter wheats, particularly second and bread-making wheats, as well as feed barley, are likely to give reliable benefits where nitrogen is the key limiting factor for yield, he notes.
“Agrovista grower trials have shown a 0.7t/ha increase when targeted at situations likely to give the best responses, a 4:1 return on investment.”
High yielding maize varieties also produce good responses – most N is applied in the seed-bed or at establishment so they can run short of N during cob fill. Agrovista trials carried out at Great Ellingham, Norfolk on 56 varieties grown on a sandy loam soil and given 60kg N by early post emergence produced a consistently higher average cob weight, with marked increases in Ramirez, Kougar, Dualto, Hobbit and Absalonf. Whatever the crop, N-Lock should be applied near the time of maximum N application, says Craig. “In winter wheat, for example, it can be tank-mixed with the T1 fungicide, while in maize it can be applied straight after drilling the pre-emergence herbicide.
“The only proviso is that the crop does need rain within 10 days of application to ensure product gets washed onto the soil, so that should be borne in mind.”
While many growers are questioning the value of inputs even more than usual given the current economic climate, Mr Green maintains they have already made the biggest investment by planting the crop.
“I’d argue that investment needs protecting – yield is king, especially when prices are under pressure.”