Effects of establishment technique and number of management passes on winter wheat production costs

Abstract

A 4-year study was undertaken with the aim of reducing the unit costs of consecutive wheat crop production without reducing output, by focusing on the interactions between lower-cost establishment and minimum pass husbandry. Replicated large block trials were conducted in fields at Andover (light chalkland soil), Cirencester (medium loam soil) and Biggleswade (heavy chalky clay loam), starting in autumn 1998 as second wheats and progressing to fourth or fifth wheats. Variables examined were establishment method (direct sowing, minimal tillage and ploughing, all in the presence of chopped straw, and all sown with the same cultivation drill), use of a take-all seed treatment (silthiofam), and number of in-crop husbandry passes. The input strategies varied slightly, but essentially compared two 'minimum' pass systems (3 and 4 core passes) with a control treatment (7 core passes), for application of nitrogen fertiliser and crop protection spray inputs.

On the chalkland soil, minimal tillage gave the highest yields and margins in all years. On the medium loam, ploughing gave the highest yield in 2001, but overall differences were small and direct sowing was the most cost-effective. No single technique was consistently best on the heavy chalky clay loam, but direct sowing was lower yielding in the second and third years, and minimal tillage gave the highest average margin over the three seasons. Direct sowing had the lowest energy cost of establishment, but gave the lowest plant populations. Minimal tillage had the lowest total energy costs per tonne of grain on both the light and heavy soils. Direct sowing resulted in less broad-leaved weeds than ploughing, but higher blackgrass and brome populations. There was also a lower incidence of eyespot and Septoria tritici after direct sowing than after ploughing.

The largest yield response to seed treatment was obtained in 1999, when it reduced take-all incidence by half. Despite having had the highest take-all levels in that first year, direct sowing showed the smallest average yield benefit on the light and medium soils. Reducing the number of input passes from 7 to 3 decreased yields at all sites in 2000. This was associated with inferior disease control, only one fungicide having been applied. There was no disadvantage to minimum pass in 2001, under lower disease pressure. However, with application and establishment costs included, the minimum pass strategies were most cost-effective overall. There were some interactions between establishment method and pass number. After ploughing, the 4-pass (with split nitrogen) was as cost-effective as the 3-pass system, whereas after direct sowing it was no better than the 7-pass. At Biggleswade, the direct-sown blocks benefited more from the 7-pass than the other establishment methods.

In a consecutive wheat crop situation, minimal tillage or direct sowing can deliver yields equal to or higher than ploughing on a range of soil types. The greatest benefit from ploughing is likely to be on medium or heavy soils after a wet autumn, or where grass weeds are a problem. Adopting minimum pass husbandry can improve profitability, when the cost of each pass is taken into account. However, for a single fungicide spray to be effective, correct application timing (at flag leaf) is vital. Lower cost establishment does not dictate that a minimum pass approach will be less successful, and the combined benefits could range from £36 to £120/ha.