Yield and oil variability in modern varieties of high-erucic winter oilseed rape ( Brassica napus L. var. oleifera) and Ethiopian mustard ( Brassica carinata A. Braun) under reduced agricultural inputs

Increasing interest in vegetable oils for use in green chemistry has stimulated research into high-erucic Brassicaceae species such as winter oilseed rape ( Brassica napus L. var. oleifera) and Ethiopian mustard ( Brassica carinata A. Braun). The objective of this study was to determine the yield response of recently released cultivars of these species under high and low production inputs. The varieties Maplus and Hearty of B. napus, and BRK1 of B. carinata were cultivated with autumn sowing in a large-scale field trial at the experimental farm of the University of Padova in Legnaro (NE Italy, 45°21′N). The genotypes were compared under high and low input management systems: high input was characterised by conventional soil tillage, chemical weed control, and high N–P–K fertilization, and low input by minimum tillage, mechanical weed control, and limited N–P–K fertilization. Oilseed rape varieties had greater seed yield than BRK1, and interactions with input level and cultivation year were significant. Maplus yielded most at high input (3.78 vs. 3.31 t ha −1 DM at low; average of two years), whereas Hearty showed no significant differences between inputs (3.49 t ha −1; average of years and inputs), indicating its better adaptability to extensive agricultural management. Yield performance of BRK1 B. carinata was very stable at varying agricultural managements, but not very high (2.73 t ha −1 on average) – a fact that may limit its competitiveness with oilseed rape in autumn sowing, especially at higher latitudes. B. carinata was also more variable across the years than oilseed rape in terms of seed yield, oil content, and percentage of erucic acid. This was mainly due to the particular climatic conditions of the second year of the experiment (mild winter; hot, dry spring) which led to considerable winter elongation and pre-flowering, and later to incomplete seed filling. In these conditions, BRK1 had both lower oil seed content (36.7% vs. 47.1%) and erucic acid (41.3% vs. 49.1%) than oilseed rapes. In general, with few exceptions, the reduction in inputs did not affect either seed oil content or the amount of erucic acid, regardless of variety and year, but seed crude proteins were reduced mainly because of N shortage.