Can seed rate decisions be improved by improved prediction of establishment

Summary Recent HGCA-funded research has demonstrated that optimum plant populations are lower than was previously thought. A lack of confidence in the prediction of the number of plants that will be established from any given seed rate has however, reduced the degree to which this knowledge can be applied. The work reported here attempts to identify and quantify the main factors affecting crop establishment, through a review of the literature and collation and analysis of extant datasets. Average establishment in the data review was 67%, significantly lower than the generally accepted benchmark of 85%, but also hiding a huge variation from 2-100%. Factors that had a large effect on establishment included drilling depth, soil aggregate size, soil moisture content, soil temperature, pests (slugs, frit fly, leatherjackets, wheat bulb fly and wireworm) and disease (fusarium and septoria). The data review highlighted drilling date, soil type, soil temperature, secondary cultivations, rolling, seed rate and variety. Whilst we could have predicted that all of these factors could be important, the magnitude of their effects was greater that we would usually allow for when making seed rate decisions. Additionally some of the factors have the scope to be monitored ‘onthe-move’ and could be used to account for within-field variability.