Response of Sunflower to Uniformity of Plant Spacing1

Abstract

AbstractPlant spacing in the row is variable in most sunflower (Helianthus annuus L.) fields. The amount of yield loss from moderately uneven stands of sunflower should be known before undertaking expensive techniques to increase uniformity of plant distribution. The objective of this research was to measure the effects of uniformity of plant distribution on sunflower seed yield, plant growth, and seed quality. Four plant distributions of oilseed and nonoilseed cultivars in rows 76 cm apart and in a population of 49,000 plants/ha were established at five locations in Minnesota in 1979 and 1980. Soils were Typic Haplaquolls, Aerie Calciaquolls, and Aerie Haplaquepts. Plant distributions were: single plants 27 cm apart; paired plants 53 cm apart; five plants each 13 cm apart, 80‐cm space; seven plants each 9 cm apart, 80‐cm space, single plant, 80 cm space. Uniformly spaced, single plants lodged least and produced heads of lowest moisture percentage at harvest and seed of highest yield and oil percentage. Yield reductions from uneven plant distributions ranged from none to 31% and averaged 10%. Greater lodging was the most consistent detriment of nonuniform plant spacing. The magnitude of differences in seed quality among the plant distributions was small and consequently of relatively little economic importance.