Managing early-drilled winter wheat: Seed rates, varieties and disease control

Abstract

This project assessed the effects of varieties, seed rate and fungicide regimes on the performance of early September sown crops of winter wheat at five sites during four growing seasons.  In the first year thirteen varieties, sown at three seed rates, were compared under a standard, three fungicide programme at four sites. In subsequent seasons the varieties Claire, Consort and Equinox were sown at two seed rates and subjected to five fungicide programmes to determine the need for adequate disease control over the longer growing season. These trials were carried out over five sites throughout England.

Seed rate effects : In general, across the five sites and four seasons, reducing seed rates led to reduced plant population, Septoria tritici and eyespot infection. Overall, however, there were consistent and significant increases in yield at the higher seed rate of between 0.3 and 0.4 t ha-1. This was achieved through an increase in ears m-2. Assuming a TGW of 44 g, and seed costs of £230 t-1 a cost-benefit analysis was made on the yield differences between seed rates of 100 and 200 or 250 seeds m2. In the season where lodging occurred, increasing seed rate led to increasing costs, due to greater lodging at the higher seed rate. In subsequent years increasing seed rate generally led to benefits, of the order of £34 ha-1 at a feed wheat price of £70 t-1.

Varietal effects :  The three varieties included in trials for detailed evaluation, Claire, Consort and Equinox, were selected on the basis of their suitability for early sowing, especially standing power, disease resistance and tillering capacity. Claire gave the highest yields and Equinox the largest TGW, and these effects were consistent across sites and seasons. Consort and Equinox had higher levels of Septoria tritici, whereas Claire was more susceptible to mildew. These results reflect ratings given in HGCA recommended lists. In 1999/00, a wider range of varieties were included in the trials; there were statistically significant interactions but these were related to lodging resistance rather than any intrinsic developmental or growth characteristics.

Fungicide effects :  During the duration of this project over five sites, covering a wide geographic area only small traces of mildew were recorded. The main disease encountered was Septoria tritici. In all seasons there were high levels of S. tritici early in the season on the lower leaves. In two seasons disease levels remained low as the year progressed; only in one season (2002/03) was there an appreciable increase in disease levels from June onwards at some sites. Additional spring fungicides only had lasting effects under conditions of high disease pressure and in the majority of site and season combinations resulted in only small yield benefits. Similarly, additional autumn fungicides had only transitory effects on disease levels and rarely led to economic yield increases. Effects of the different fungicide treatments were not influenced by seed rate whilst varietal response corresponded closely to resistance rankings to individual pathogens, but these were only seen in years of high disease pressure. Only at the Kent site in one season was there a significant economic benefit from the application of an additional spring fungicide.

This is the final report of a 51-month project that started in August 1999. The work was funded by a contract of £252,797 from HGCA.