Effect of Topdressing Different Nitrogen Fertilizers on the Growth, Physiology and Yield of Rapeseed (Brassica napus L.)

PurposeA reasonable application of nitrogen (N) fertilizer plays an important role in improving rapeseed cultivation and promoting oilseed yield. Therefore, the application effect of topdressing different N forms in dryland soil on the growth, physiology and yield of rapeseed were investigated.

MethodsOne cultivar rapeseed Xiangyou 15 was cultured in dryland soil under topdressing the same N rate and three treatments were set up, including single application of nitrate N (NO₃⁻) (A), 1∶1 application of nitrate and ammonium N (B) and single application of ammonium N (NH₄⁺) (C). The agronomic traits, seed yields, oil content, dry weight, N accumulations, photosynthesis and nitrate reductase (NR) activity in rapeseed were analyzed at different growth stages.

ResultsCompared with A treatment, effective pod per plant and seed yield were significantly improved under C treatment (P<0.05); the flower (pod), stalk and total above-ground biomass and N accumulation of flower (pod), leaf, stalk, seed, above-ground organ at the flowering and harvest period were significantly increased under B and C treatment (P<0.05), respectively; the SPAD values, net photosynthetic rate, stomatal conductance, intercellular CO₂ concentration at the seedling and flowering period, and NR activity in leaf at the flowering period were strengthened under B and C treatment, but NR activity at the seedling period was lowered.

Conclutions Compared with single application of nitrate, the aboveground biomass and grain yield of rapeseed could be significantly improved by single application of ammonium in dryland soil.