Adapting agronomy to the season’s challenges
With wet conditions limiting drilling opportunities and crop vigour, how should farmers adapt management this spring? ...
Martin Rickatson joined a farmer and agronomist group convened by Hutchinsons to share views.
While bare land and backward crops dominate the combinable crop landscape as spring approaches, taking some bold management decisions in areas such as fertiliser and nutrient investment could help to get the most out of cereals with potential and help cut losses on others.
That was the consensus among a group convened recently by agronomy firm Hutchinsons to discuss ways farmers can plan for the spring and for the remainder of this crop year.
BASIS-qualified farmer Andrew Pitts hosted Hutchinsons agronomist Michael Shemilt, plus the firm’s UK technical manager Dick Neale and UK technical support manager Neil Watson, to discuss what this means for crop care this spring.
Keeping a cool head will be essential this spring, because messing up field management – whether on an existing winter crop or ahead of a spring one – will have long-term effects, said Mr Neale.
“For those still with bare ground, whether they are considering a spring crop, a break crop or even fallow as an entry for winter wheat, the variation in margin can be relatively minimal, at about £10-15/hectare, but might be more like £100/ha if soils are further damaged and there is a legacy for the next crop,” he said.
“Calculate whether you are doing the right thing. Farming is not about one year and this is a new ‘year one’ in many rotations.”
ROOTING, TILLERING AND SOILS
Setting the scene to illustrate how soil health influences early growth and a wheat crop’s ultimate performance, Mr Watson pointed to the importance of GS30-31, when tiller and spikelet production take place.
“The foundation period from drilling to GS30, when the crop moves from vegetative to apical growth, is critical, but at GS30 it will have only 10 per cent of its final biomass,” he said.
“It needs sufficient root development to sustain this, and make use of available water and nutrition to develop it through the next critical stages, with a hectare of wheat putting on a tonne of biomass every five days after GS30.
Many crops currently may look green on top, but they do not have the root mass underneath to absorb sufficient nutrients and support this.
While many early-drilled crops have more than enough tillers to support decent yield potential, it is a different story for the later-sown ones-the majority.”
The number of leaves emerged determines tiller production, and once plants are beyond the three-leaf stage, every additional leaf axial produces a tiller, these then also produce tillers, explained Mr Watson.
“But while tillers can be managed and manipulated, they cannot be created, so tiller number is pretty much fixed by establishment date, and the difference can be significant,” he said.
“A September-drilled crop planted in warmer soils could perhaps emerge in seven days, and produce nine leaves and maybe 37-38 tillers – although crop competition will limit this potential.
In contrast, a November-sown crop may produce perhaps five leaves and 10 or 11 tillers, because soil temperatures will have probably halved over that time, and this will limit its photosynthetic ability.”
Mr Neale acknowledged that having soils with good structure and drainage gives crops a head start, but that this will not compensate for the many other challenges they face.
“Well-structured soil will recover quickly even if the crop above might not yet be looking so good, but late establishment meant many crops lost thermal time, and a poor foundation, with difficult conditions, wet and cold weather and other issues, means good 2020 harvest yields are already unlikely,” he said.
Role for PGRs:
With the number of leaves emerged determining tiller production, and this in turn depending on drilling date and the weather that follows, tiller numbers cannot be boosted thereafter, but they can be protected, said Mr Watson.
“Use the AHDB wheat growth guide to help gauge your crop potential based on when it was drilled, thermal time since drilling, and how many leaves and tillers the crop will produce,” he said.
“Nutrition is key to tiller survival and development, and plants must have enough nitrogen around their roots to support growth. While utilisation varies depending on factors such as root structure, soil structure and soil moisture, if they cannot detect sufficient nutrition below ground plants will sacrifice tillers above it.
This is where, although they are unlikely to be needed this year to control straw height and lodging, PGRs have a role to play in tiller survival and size. If there are say five tiller buds on a plant, with the main stem plus three tillers growing but two tiller buds yet to burst, the former will dominate and demand food, depriving the latter and limiting their potential.
That is why growth regulation is critical to suppress apical dominance in the main stem and established tillers, and ensure sufficient nutrition is made available to the tiller buds waiting to burst.
But remember, there is no point applying PGR to manipulate tillers if you have not applied sufficient nitrogen to drive the growth.”
Wheats will require a good dose of nitrogen early to give them a kick, but no more than 80kg/hectare, suggested Mr Neale.
“Because we have had so much rain, it may be advisable to use NPK+S almost regardless of index, and second wheats especially will need the sulphur to boost leaf size and tiller survival,” he said. “A dose of 20kg/ha as soon as travel is possible will help roots as they deepen.
“Adding phosphite pre-GS31 – ideally mid-tillering to GS30 – with a PGR will also help counter take-all and drive growth of root tips, the short-lived but most efficient root parts.
A product such as Advance 66 combines phosphite with zinc – which is manipulative rather than nutritional, keeping paths open for other nutrients-and a trinexapac-ethyl PGR will work faster and be less aggressive than chlormequat in cold temperatures.”
Mr Neale suggested this is not the season for cheaper forms of nitrogen because of their long-release time. “Crops may need an early slug of nitrogen to kick them on, and few can afford urea’s conversion lag of up to two weeks,” he said.
“In addition, in cold soils bacteria will become dormant over winter and in spring may still be locking up nitrogen to break down chopped straw.
If you have already bought a cheaper product, consider storing it until next year, and investing in good quality ammonium nitrate.”
Phosphate and potash:
Mr Neale said: “Phosphate should be the next most important concern, with more than 100 of 200 crops in the Yield Enhancement Network showing an average 0.7 tonnes/ha yield response to additional early P.
Potassium is not stored within the plant, and crops generally do not take off anywhere near the amount the plant requires during growth, so while K enhances N activity and helps reduce lodging, if indices are sound then additional K is not required.
Whatever you do, look beyond last year. Aim to maximise the performance this year of your best crops, but perhaps reduce inputs on the poorest fields and cut your losses on unestablished ones where sensible, to look ahead to next year.”