Trials show value of stronger varieties in ‘lower input’ regimes

John Miles, Agrii seed technical manager, explains why variety choice is the primary consideration when planning cultivation regime, drilling date and fungicide strategy

Not all varieties perform equally.  It may seem an obvious statement to make, but it promotes the bigger question: which will do well on my farm, and which won’t?  Given the interest in reduced tillage and other lower input forms of production, this seemed a question worthy of investigation.

Through a series of fully replicated trials at farms in Huntingdon, Essex, Kent and Dorset in 2021-22, Agrii investigated the relative performance of wheat varieties under different establishment regimes and crop protection programmes.  The objective was to understand the impact on output from direct drilling over deep cultivations and how does this influence disease pressure and, specifically, the opportunity to incorporate biological crop protection agents in place of conventional fungicides.

Direct drilled crops did better at the Huntingdon trial site largely due to good conditions at the time of sowing

On the face of it there was little to separate either establishment regime.  Across all 18 varieties grown side-by-side in Huntingdon and Essex, the average yield under direct drilling and plough-based regimes were almost identical at 10.6t/ha.  But this average hid a wide range in performance and there were clear differences between the sites, varieties and regimes. The seed rate for direct drilled plots was raised to 425 seeds per metre compared with the plough at 350. The aim was to achieve the same plant stand in both techniques.

On the Hanslope series clay at the Huntingdon site, direct drilled crops faired best, but the question is why? Ear counts were only slightly better at +7% and while plant counts were similar ahead of the winter.  NDVI aerial imagery captured by Bayer in the New Year reveal the impact that the wet weather in January had on plant biomass.  The result, where the direct drilled plots outyielded those sown following the plough, was not entirely unexpected given the biomass differences which remained all season. We believe in this instance the ploughed ground held onto too much moisture, so the plant environment became adverse during February resulting in loss of biomass shown by the NDVI image. 

The NDVI image reveals the impact of the wet winter on plant biomass in the plots sown after drilling. Picture courtesy of Bayer.

Agrii Huntingdon variety establishment trial

 Average yield (t/ha)Plant count (plants/m2)Establishment rate (%)Ear count (ears/m2)
Direct drilled12.418242447

Reference: Agrii, 2022

In Essex, also on Hanslope series clay, plant populations and ear counts were similar, but the average yield was lower at 9.17t/ha, down 2.87t/ha on Huntingdon. On this site, the plough-based approach produced the better result.  This may in part be due to the establishment challenges the direct drilled plots faced as a result of large quantities of chaff in the straw swath even though the straw was removed.

This farm has been in continuous wheat for 40 years and damp conditions at drilling and persistent slug activity were evident.  Unsurprisingly, the ploughing effectively buried this impediment (trash) giving a uniform crop.  Plant and ear counts were not taken from any bare patches, so where establishment is good, it is comparable across systems. Like the Huntingdon site, seed rate adjustments have given similar plant stands and emergence percentages.

Agrii Essex variety establishment trial

 Average yield (t/ha)Plant count (plants/m2)Establishment rate (%)Ear count
Direct drilled8.919746435

Reference: Agrii, 2022

The variety performance at both the Essex and Huntingdon sites was also telling.  On the higher-yielding Huntingdon site, the varieties standing out for relatively better direct drill versus plough performance were similar to those that stood-out overall.  Their direct drilling advantage was, however, much greater here at more than 1 t/ha.  Equally, only three varieties performed less well under direct drilling.

Good and bad performers in the Agrii direct-drilled variety trials

Varieties that yielded at least 0.25t/ha over the trial averageVarieties that yielded at least 0.25t/ha under the trial average
GrahamLG SkyscraperSkyfallRGT Wolverine
GleamGrahamLG TapestryMayflower
LG SkyscraperKWS ExtaseKWS CraniumLG Typhoon
KWS ExtaseTheodoreRGT Silversurfer 
KWS DawsumGleamMayflower 
RGT WolverineKWS ZyattLG Astronomer 
Theodore LG Typhoon 

Reference: Agrii, 2022

On the lower yielding Essex site where the direct drilling challenge was greater due to the quantity of surface trash, every variety performed better after ploughing than direct drilling.  Those returning the least variation (no more than 0.4t/ha) in comparison with their yield under the plough-based regime were: LG Astronomer, RGT Saki, KWS Zyatt, Crusoe and Gleam.

This is only a single year, so the performance of the different varieties could have as much to do with their relative suitability to the season as to the different regimes.  Even so, it appears that where establishment conditions are good, direct drilling can be advantageous for almost all varieties, with some doing especially well.  

Where direct drilling establishment conditions are more challenging, it looks like the more vigorous varieties are better able to compensate.  This is knowledge growers can use to their advantage when planning cultivation strategies and cropping plans. Growers know when they are likely to push the limits of drilling date, soil type, crop or weed residues or cover crop trash, so can respond accordingly by choosing varieties better suited to these conditions.  It is also worth noting that across the trials, there were several varieties that did well regardless.  KWS Extase, Gleam, Graham and LG Skyscraper were all consistently among the best performing varieties. They may not be the most best performing when conditions are perfect, but they can be relied on when it matters.  

Early versus late drilling

The Dorset trial followed the same protocols as those in Huntingdon and Essex, but investigated the performance of two, high-yielding feed wheats: Gleam and Fitzroy.  The findings were much the same: the more robust the variety, the better suited it is to direct drilling.

Across the two regimes – early and late sowing and direct drilling versus after ploughing – both varieties averaged about 12.75t/ha on the light land. The site is well-suited to direct drilling given the high sand content of the soil and is reasonably black-grass-free.  This perhaps explains the owner’s preference for direct drilling over deep cultivations.

Unsurprisingly, early October drilling gave a yield advantage of almost 2t/ha over drilling almost exactly a month later.  And the 2.7t/ha advantage shown by Fitzroy was more than twice that of the 1.1 t/ha of much less disease-resistant, Gleam (see figure 1).  This serves as an example of the having a drilling strategy that matches variety choice to drilling date and establishment regime.

Figure 1: Agrii Dorset establishment trial
Reference: Agrii, 2022

The quirk of the autumn weather also forced a change in plans that served as an opportunity to explore the relative value of disease resistance under each establishment regime.  While we were able to direct drill the Dorset ground under the well-established no-till regime at the end of the first week in October, we couldn’t sow the ploughed land for a further month.  This gave us a golden opportunity to show how delayed drilling influenced Septoria pressure in what turned out to be a dry season.

Across both varieties in the untreated plots, just over 36% of the area of the top three leaves was suffering from Septoria tritici in the earlier-sown crops by mid-June compared with around 26% in the later-sown ones.  Reflecting their different levels of Septoria resistance, this varied from 28% and 22% respectively with Fiztroy to 45% and 30% with Gleam.

A robust fungicide programme reduced Septoria levels to an average of 10% and 3% for the earlier and later sowings, improving average variety yields by over 1t/ha.

The difference in both yield and fungicide response between the two varieties in the earlier drilling, higher-Septoria-pressure-slot, was most revelling.  Under the robust programme, Fitzroy averaged 14.18t/ha – just over 0.5t/ha up on its untreated performance – while, at 13.35t/ha, Gleam gave a response of fully 1.9t/ha.  The yield response of Gleam is impressive, but it also highlights the risks that occur when the level of variety resistance is towards the lower end of suitability for the situation.

This underlines the value of a variety like Fitzroy with its Septoria – not to mention yellow and brown rust – resistance superiority.  Its robustness allowed the variety to take much greater advantage of the extra performance opportunity offered by earlier drilling than Gleam.

Where the regime and conditions allow earlier drilling, there can be little doubt about the extra value of the likes of Fitzroy – not least in providing leeway to cope when even the best laid plans are interrupted.

The opportunity that more robust varieties offer extends beyond drilling date and establishment regime. For growers wishing to incorporate biological products in place of traditional fungicide chemistry the value of stronger varieties was further demonstrated in a large-scale 14-variety trial with a broad range of treatment programmes at a separate Kent site invariably hit by all the main foliar diseases.

All the programmes involved four treatments at three-weekly intervals in a season in which early disease pressures were relatively low. Despite this, the average response across all varieties to the Agrii strong fungicide programme was over 2t/ha.

This varied from an average of almost 3t/ha for the three varieties with the lowest untreated yields to only 1t/ha for three with the best untreated performance (see figure 2).

Figure 2: Agrii Kent disease management trials

Reference: Agrii, 2022

At 2022 season costs and crop values, the margin advantage from employing the strong fungicide programme increased from just under £500/ha with the most robust varieties to almost £1000/ha with the least robust.

Replacing multi-site folpet with the biologicals, Iodus (laminarin) at T0 and Thiopron (sulphur) at T1 had a slightly negative effect on yield and margins with the least robust varieties.  And replacing all the chemistry with biologicals at T0 and T1 in our reduced fungicide with crop health treatment knocked performance even further.

The fact that yields were still well above untreated levels in both cases shows the contribution of the biologicals in the context of the 2022 season and with the backup of robust T2 and T3 chemistry in protecting performance once infection levels increased.

With the more robust varieties, however, there was little loss in performance from the reduced fungicide programme with better crop health and the strong fungicide programme replacing folpet performing better on average than the strong programme alone.

This underlines the greater opportunity growers have for incorporating biological products in place of chemistry in their treatment programme where they have the most robust varieties – providing, of course, early disease pressures are not too high, and they are able to maintain a well-timed programme and are prepared to use fungicides at T2 and T3.

It also reinforces the risk run by those trying to do the same thing with less robust wheats despite favourable early season conditions and a similarly well-timed and robust T2 and T3 programmes.