Estimating loss in grain yield due to suboptimal plant density and non-uniformity in plant spacing

Abstract

The percentage loss in grain yield for a crop of raingrown sunflower was quantified, using a multiple regression technique, for 9 combinations of plant density and uniformity in plant spacing. For each combination, partitioning loss in grain yield involved the reduction in grain yield (g/m2), the number of plants involved and the effective area of crop which those plants represented (m2). Relative to an achievable yield potential of 692 kg/ha, any reduction in grain yield was mainly due to the lack of plants at a density less than 5.00/m2 (7.4% yield reduction) and to non-uniformity in plant spacing at a density greater than 5.001m2 (5.6% yield reduction). The multiple regression technique is considered more valuable than other methods because it provides quantitative estimates of per cent loss in grain yield attributable to suboptimal plant density and non-uniformity in plant spacing. The technique should be of value in assessing the effect of poor crop establishment at a site or in evaluating improved crop establishment. A more general relationship capable of predicting per cent loss in grain yield based on data taken at the time of establishment is still required.