CropTec show round up

The seminars at the recently-held CropTec event covered topics including crop protection, crop nutrition, crop breeding and crop establishment, and were a popular destination for farmers and agronomists alike. Heather Briggs reports.

Sulphur is an often overlooked yet essential plant nutrient which is a building block of crop yield and quality, said Yara UK agronomist Natalie Wood. 

Sulphur is also linked with nitrogen efficiency; which may be because both elements are involved in the formation of protein and chlorophyll and are linked in the conversion of nitrate to amino acids.

Sources of sulphur include mineralisation from organic matter in the soil, but in many cases these are now depleted, and using organic manure is not a reliable source, she said.

“Even if sulphur is present in the soil it does not mean it is available for the plant to uptake. This makes it hard to build reserves in the soil.”

Deposition from the atmosphere used to be one of the main sources of the mineral, but with the fall in pollution levels it can no longer be considered a viable source.

“Mineral fertilisers are the most reliable way to ensure the crop has a supply of sulphur; those which contain sulphate sulphur are the best because it means that the sulphur is already available rather than having to mineralise in the soil before being taken up.”

Soil type can also make a difference to uptake; lighter soils are more prone to deficiency as they are more prone to leaching, said Ms Wood.

“Loamy sand could see up to 85 per cent of sulphur being leached; so if you apply 60kg/ha of SO3 in February, 51kg/ha could have leached by May, which is right in the period of active growth.”

She would normally recommend 40–50Kg/ha for cereals and 70–80kg/ha for oilseed rape, but if growers are on a responsive site, they may find they need up to a further 30kg/ha. 

However, detecting insufficient supply can be challenging as soil analysis tests are not always reliable, so grain analysis tends to be undertaken after harvest to find out how well the sulphur strategy had worked. 

“This is not ideal, but it gives you an idea so you can tweak your strategy for the next year.”

Potassium (K) is another important mineral, playing a key role in water use efficiency, which becomes more evident under drought conditions.

“It is present in the guard cells of the stomata, which control water regulation. As a result, if it is deficient, these will not work as efficiently and the plant will lose more water through transpiration.

“This is increasingly important as we are pushing N rates and getting bigger crops but have recently had increasingly dry springs.”

Compared with N and P, K is taken up in a short time-space, with uptake of up to 7.7kg/ha/K/day during the rapid growth phase. During this time, N uptake is 4.5kg/ha/day and P is 1.6kg/ha/day.

“Independent of soil indices, I would recommend applications of 35kg/K/ha in spring, so it is available to the plant at this crucial time. 

“If you are below Index 1, you will need an autumn application as well for establishment, as well as the necessary 35kg/ha in spring when crop demand is so high,” she concluded.

Better spraying accuracy

Hitting your target when spraying is crucial to efficacy, according to Syngenta New Farming Technologies specialist Sam Stephenson.

Wind speed, which can fluctuate dramatically even while the spray operator is in the field, will have a huge influence on spray pattern and coverage, along with potential drift. 

“The mantra is ‘Go low; Go slow; Get covered’,” said Mr Stephenson.

“The slower you go, the better; Dutch farmers typically travel at just 6kph. It is much easier for the active to hit target at this speed, but would have huge implications for sprayer output and covering large acreages.” 

Where spray operators are travelling at 16kph or more, however, boom stability and resulting turbulence behind the sprayer will affect how much active hits the target. 

“It’s about finding the optimum compromise between efficiency and efficacy, which will be different for all farms and situations.”

When it comes to black-grass control, he reported Syngenta trials have repeatedly shown higher water volumes can help improve coverage and results.

“In perfect conditions 100-litres/ha may deliver adequate results, but where chemistry is applied at 200-litres/ha, we have seen consistently better and more reliable control. 

“Working at 400-litres/ha has shown marginal further improvements, but is really time-consuming to do; in practice it is probably only worthwhile with very high value crops.  

“Future precision application is likely to improve as innovations in spore traps, weather stations, management systems and application maps become commercially available,” he added. 

Future-proofed Lists 

Increasing pest resistance and withdrawal of plant protection products means that technical solutions from crop genetics are likely to play an increasingly important role in the Recommended List (RL), said AHDB senior crop production systems scientist and RL lead Jenna Watts.

The current RL project is due to stay in place until 2021, but it needs to continue to provide useful information on appropriate varieties for regional, agronomic and end-use requirements.

“We are taking a close look at our systems; while the treated yields show genetic potential, there are other areas that growers would like to see such as yields under commercial situations,” said Dr Watts.

Additionally, as control of septoria tritici using azoles and SDHIs is becoming more difficult, and there is mounting light leaf spot resistance to azoles in oilseed rape, the agronomic package may need to have a different weighting in the future, she added.

The RL may also need to include varietal resistance to new pests and diseases, or those whose geographical spread has broadened. 

Explaining a little of how the RL works, she emphasised that getting a variety onto the RL is challenging, as from over 800 which enter the initial trials, 3–6 are finally accepted after 5 years.

“We are looking for a balance of features; first we have a yield target; if it is above the comparator varieties, it can expect to be recommended unless it has important weaknesses. 

“If it is below that, it would need to have additional strengths – if it is more than two per cent below the comparator’s yield, it would only be recommended if it had something special, such as innovative traits. 

“As we move forward we may also be looking for better photosynthetic efficiency, drought tolerance, early flowering as well as insect and disease resistance,” she added. 

Designing future wheat

Lack of genetic diversity makes the design of future wheat more difficult, warned NIAB director of genetics and breeding Alison Bentley.

Wheat is subject to demanding end-use requirements, which has led to focused breeding programmes, she explained, adding that one of the most important lines is from Robigus which is a parent, grandparent, or great-grandparent of many of the varieties currently grown.

“Understanding the reasons behind the popularity of Robigus is key, but it also reflects the narrow genetic base we have for wheat to work from.”  

To address this and help drive development of new wheat germplasm containing the next generation of key traits, a five-year project looking at genetic materials has been funded by BBSRC.

“Modern wheat occurred from a chance hybridisation between Wild Emmer (triticum dicoccoides) and Wild Goat Grass (Aegilops tauschii),” explained Dr Bentley. 

“Wild Emmer also developed into durum wheat and these goat grasses still grow naturally in the wild, so we have been able to recreate the natural event by crossing durum wheat with goat grass; and then crossing it with Robigus.

“We hope they will provide useful variation for disease and agronomic traits , especially nutrient use.”

Other work being done within the project includes exploring the possibility of increasing efficiency and sustainability, enhanced health benefits and durable pest and disease resistance.

Soil science

Soil, engineering and hydrological datasets are being combined to update and improve a free-to-use UK Soil Observatory website, said British Geological Survey’s Henry Holbrook.

New soil descriptions are planned, to provide useful information for growers and agronomists on soil characteristics and the foundations that influence texture, structure, drainage and chemistry across our landscape.

The work will highlight areas of soils likely to be prone to compaction and run-off. Both these problems can occur as a result of physical properties such as clay content and aggregate stability of the soil.

Soil moisture and its variation between fields is another area of focus, with the aim of building better understanding of soil-water processes to provide real-time values to forecast possible changes in soil moisture. 

“Knowing soil moisture levels and how they are likely to change will help growers make decisions about when to take heavy machinery on the land.”