Article taken from Agronomist & Arable Farmer, July 2018, written by Agrovista Technical Manager Chris Martin.
The theoretical yield potential of wheat across the UK over the past five years has been around 20t/ha.
The average farm yield over this period is around 40% of this potential, while the highest yielders have achieved 60%, and in some years even 70%, of that figure.
Wheat yield is determined by three key factors. Firstly, available natural resources such as solar energy, carbon dioxide and water, secondly their capture and thirdly their conversion to harvestable grain.
Within a region, we receive similar available natural resources, and the conversion to harvestable grain (harvest index) is believed to be more determined by variety choice than by crop husbandry. This means top growers must be excelling in the capture of these natural resources.
In a normal season in the UK, on a moisture retentive soil, light is normally the limiting factor. As yields rise, however, water limitation becomes more common.
Light capture is determined by maintaining a green healthy canopy for as long as possible. The theory would tell us that for every day we maintain green leaf area above 37%, we should produce an extra yield of 150 kg/ha per day.
This is very much borne out in fungicide trials, where an extra week of good disease protection is regularly producing an extra tonne per hectare. Therefore, appropriate fungicide and nutrition programmes are obviously key to prolonging green canopy longevity and hence improve light capture.
Water capture depends mainly on rooting depth, which in turn is very closely linked to soil structure. Agrovista has set up a series of regional trials across the UK to explore how to practically improve capture of our natural resources and bridge this gap between the average and best performers.
To complement the regional trial sites and really get a handle on what is happening at farm level, this autumn Agrovista is launching a national yield competition designed to combine the best theoretical and practical approaches in agronomy and crop husbandry.
From this, we will create blueprints on how best to capture our available natural resources in individual varieties across a range of different growing scenarios.
This follows a prototype competition in the north of the UK, launched this spring, which already has over 60 entries.
The idea of the competition is for farmers and agronomists to work closely together to explore opportunities to maximise crop potential. The aim is to push crops a bit harder, looking at establishment, nutrition and bioscience from the soil upwards.
During the competition, several measurements will be taken at key growth stages, including plant numbers, tiller counts, ear number assessments and, ultimately, a final yield figure. The findings could also be linked to cultivation techniques.
Approaches and results can then be compared to those achieved under the farm standard on other parts of the field or farm, to identify which principles could be adopted or warrant further investigation.
The intention is to pull all this together at a grower conference the autumn after the competition to discuss findings, share experiences and to host a range of experts who can relay the latest thoughts and insights on soil health, crop establishment and input agronomy.
While benchmarks have been used for many years and are a good guide to assess crop growth throughout the season, indications from the top yielders in the ADAS YEN competition over the past few seasons are that for significantly higher yields, some of these benchmarks may need re-addressing.
For example, to achieve an nt/ha crop HGCA guidelines suggest 460 fertile ears/m2, whereas the top yielders in the YEN competition had significantly thicker crops, with over 700 fertile ears/m2.
I hope, among other things, the competition will highlight if and where changes to established benchmarks need to be made. This approach is likely to require increased nutrition, growth regulation and fungicide programmes, as well as better rooting to allow more water uptake, and it's the viability of this sort of system which we are looking to evaluate from this yield competition.
Contact your local Agrovista agronomist to find out more, to enter the competition this autumn and help to maximise your farm's agronomic potential.
Appropriate input programmes
Fungicide programmes can be heavily influenced by seasonal factors, with due regard for weather, disease pressure, variety and drilling date.
However, a comprehensive strategy that includes SDHI chemistry at TI and T2 plus a multisite product, backed up by suitable rates of triazoles chemistry (higher than they used to be due to shifts in S tritici resistance) has been shown to give the biggest yield response.
Where high outputs are expected, such programmes will almost always pay. They are very likely to feature widely in the competition.
Comprehensive nutrition management will also be vital. Nutrition levels should be based on a realistic potential yield - using the farm's five-year average as a good start.
It is worth remembering that some fertiliser recommendations are based on average yields of around 8-9t/ha and must be adjusted upwards to match higher potential yields.
Many fields are capable of producing up to 15t/ha these days.
All key nutrients, not just macronutrients, must be managed. In addition to carbon, hydrogen and nitrogen, there are 13 essential nutrients that need to be readily available to produce a healthy wheat crop. If just one is in short supply, yield potential can be compromised.
Soil sampling and ongoing leaf tissue analysis should be used to fine-tune nutrient inputs to ensure an adequate supply at all times.
A comprehensive P_GR programme is excellent insurance, certainly on highyielding crops. Being well fed and well protected, they will be lush and green for longer, all other things considered, and could well be more prone to lodging later in the season.
Soil health
It is becoming very clear that we have been abusing soils for far too long, often overcultivating in unsuitable conditions which has led to a loss of structure and poor drainage.
The resulting tight, anaerobic soils can drastically limit yield potential. We need to focus on regenerative programmes that will restore our soils to the healthy, biologically rich medium our grandfathers started out with.
It is very likely that the competition will highlight the restrictive nature of many of our arable soils.
Metal will never improve a soil unless it has an inherent structural problem, and only then initially, providing the channels that will allow biology - roots, worms, bacteria, fungi - to restore the porosity that enables a soil to live and breathe. Using metal on a healthy soil can damage it, rather than offering any benefit.
That said, we know zero-till is not for everyone, but we can all do less when it comes to cultivations, and that is the avenue we should all be exploring, in combination with other proven beneficial techniques such as cover crops.