Effect of straw return with nitrogen fertilizer on photosynthetic characteristics and yield of rice in soda saline–alkali rice paddy fields

Many studies have shown that straw return to the field can promote the production of photosynthetic material for crops, and thus increase crop yields. Due to the different effects of straw return to the field in different areas, there are fewer studies on the photosynthetic characteristics and yield of rice after straw return to the field in Northeast soda saline–alkali rice area, and it is not clear whether straw return reduces the amount of nitrogen fertilizer used in the area. Using the local large-scale cultivar Baijing 1 as the material, we studied the effects of straw return with nitrogen fertilizer (0, 90, 180, 270 and 360 kg ha −1 ) on the photosynthetic characteristics and seed yield of rice in saline–sodic areas through a 2 years field trial. The results of this experiment showed that rice yield was highly significantly and positively correlated with canopy total photosynthetically active radiation (TIPAR), leaf area index (LAI), relative chlorophyll content (SPAD), net photosynthetic rate ( P n ), stomatal conductance ( g s ), transpiration rate ( T r ), Rubisco activity and PSII maximum photochemical efficiency ( F v / F m ) but significantly and negatively correlated with intercellular CO 2 concentration ( C i ). Compared with the treatment without straw return, straw return increased TIPAR, LAI, SPAD, P n , g s , T r and yield of rice when N ≥ 180 kg N ha −1 . The rice yield was the highest when the nitrogen application rate was 270 kg ha −1 . The yield of straw return treatment under this nitrogen fertilizer was 8.01 t ha −1 , and the yield of no straw return treatment was 7.52 t ha −1 (average 2 years). In addition, the results suggested that approximately 36–43% of chemical N fertilizer reduction would not affect rice yield with straw addition. Our results suggest that straw return is a promising management practice in soda saline–alkali rice areas that can reduce the application of mineral nitrogen fertilizer without losing rice yield.