The effect of substituting the nitrogen fertilizer with farmyard manure on the growth and yield of winter rapeseed in a drought-prone region

Reducing nitrogenous chemical fertilizers (CF) by partially substituting CF with farmyard manure (FYM) can increase the effectiveness of CF and improve environmental conditions by enhancing soil quality. A field trial was conducted to evaluate the effects of different rates of FYM (0, 10, 20, 30, and 40 t ha –1 , designated as FYM 0 , FYM 10 , FYM 20, FYM 30 , and FYM 40 , respectively) combined with various levels of nitrogen fertilizer (0, 50%, 75%, and 100% of the recommended dose, designated as N 0 , N 50 , N 75 , and N 100 , respectively) on the growth and yield of winter rapeseed in northwest Iran. Increasing the application of FYM and nitrogen improved the greenness index, plant height, and days to maturity. Plants grown with FYM 40 and FYM 30 had the highest number of lateral branches. Application of FYM above 20 t ha –1 significantly increased growth characteristics and economic yield. However, there was no significant difference between N 75 and N 100 . Application of high fertilizer levels of reduced silique length. The highest number of siliques was recorded under FYM 40 + N 75 (178) and FYM 40 + N 100 (175). The highest grain yield was observed with FYM 40 + N 75 (1,221 kg ha –1 ). The highest oil content was recorded with FYM 20 + N 100 (44%). The results showed that FYM above 10 t ha –1 , combined with 75% of the recommended nitrogen dose, provide acceptable rapeseed performance. Replacing 25% of CF with FYM 20 can increase rapeseed yield.