Straw and nitrogen amendments improve soil, rice yield, and roots in a saline sodic soil

Straw return can improve the physical properties and nutrient status of the soil. However, there are few studies on straw return coupled with nitrogen (N) fertilizer for rice planting in saline sodic areas. Therefore, we conducted a two-year field experiment to evaluate the effects of straw management (retention or removal) with N fertilizer (0, 90, 180, 270 and 360 kg N ha−1) on soil properties, root characteristics, rice yield and N use efficiency in a saline sodic rice growing area. The results showed that straw return significantly reduced soil bulk density, pH, soil electrical conductivity of saturated paste extraction (ECe), exchangeable sodium (ENa+), exchangeable sodium percentage (ESP), and also significantly increased soil organic matter and cation exchange capacity (CEC). Compared with straw removal, straw return reduced soil pH, ECe, ENa+, and ESP by 2.97%, 10.90%, 8.95%, and 13.78%, respectively. At the same N level, straw retention reduced rice root morphology and root vigor at mid-tillering and panicle initiation, but N fertilizer was able to alleviate root inhibition by straw return. Straw return improved root morphology and root vigor in mid and late rice growth and promoted nutrient uptake. Compared with straw removal, the agronomic efficiency nitrogen and partial factor productivity were significantly increased by 13.97% and 4.59%, respectively, in the straw return treatment. With or without straw retention, rice yield increased and then decreased with increasing N fertilizer application rate, and was maximum at 270 kg N ha−1. Compared to straw removal, rice yield was significantly increased by 4.37% (2020) and 7.17% (2021) for straw return treatments, respectively. Meanwhile, straw return can reduce mineral N fertilizer inputs by about 36–43% without affecting rice yield. Under straw return conditions, soil characteristics, root characteristics, and rice yield were optimal at 270 kg N ha−1. Our results suggest that straw return combined with nitrogen fertilization may be a promising management practice to reduce mineral N application without loss of rice yield in saline sodic soils. Among them, straw return combined with 270 kg N ha−1 was most effective in the early stages of straw return in saline sodic rice growing areas.