Effect of moisture, nitrogen rates, and soil acidity on seed yield and chemical composition of winter oilseed rape cultivars

Abstract

Seven cultivars and strains of winter oilseed rape (Brassica napus L.) were tested for tolerance to drought and soil acidity and for response to nitrogen fertilization. Plants were grown in ceramic cylinders (with no bottoms) buried to ground level at a field site in Poland. Cylinders contained a gray brown podzolic soil having a medium sandy texture and variable pH due to history of fertilization. Periodic drought (from early budding to late flowering) was imposed by covering the field plots with polythene film. Rainfall excluded by the film was compensated by watering the non‐stressed plants. Based on seed yields, rape cultivars and strains differed significantly in tolerance to drought. ‘Jet Neuf’ was most tolerant and ‘Bolko’ least tolerant. Cultivars also differed significantly in response to N fertilization, with Bolko being the most responsive cultivar tested. Rapeseed yields were generally reduced by 20% at a soil pH of 4.2, compared with pH 6.2 (determined in 1M KC1), but cultivars did not differ significantly in acid soil tolerance. Specific yield‐limiting factors in the acid soil were not identified, but a mild A1 toxicity was suspected. A higher level of acid soil (A1) toxicity will be needed to study A1 × drought × rape genotype interactions. Reductions in soil moisture or pH levels did not significantly affect the fat and protein contents of rapeseed. Variations in fat and protein contents observed were due largely to cultivar differences. Jet Neuf tended to have the highest protein and the lowest fat content. ‘Jantar’ was the highest in fat content and one of the lowest in protein content.