Reduced chemical application with bio-organic fertilizer to improve grain filling characteristics and fertilizer partial productivity of highland barley under irrigation regimes

Reduction of nitrogen fertilizer and simultaneously application of bio-organic fertilizer is regarded as an essential approach for realizing sustainable agricultural development. Substituting partial chemical N with bio-organic fertilizer is an environmentally friendly; reduce the risk of environmental pollution due to N losses. However, the appropriate rate of bio-organic fertilizer of highland barley in China is unknown. To clarify the effect of reducing chemical fertilizer and adding bio-organic fertilizer on the grain filling characteristics and yield of highland barley after anthesis under different deficit irrigation amounts in Hexi irrigation area. Under the field test environment for two consecutive years, the differences in grain dry weight after anthesis, grain filling rate, fertilizer partial productivity and yield of highland barley were determined by irrigating once (W1) and twice (W2) during the whole growth period under the no fertilizer T1, N, P, K recommended fertilization T2, T3, T4 and T5 (the total amount of N, P, K recommended fertilizer was reduced by 15%, 30%, and 45%, and bio-organic fertilizer was increased by 30%, 60% and 90%, respectively. Grain filling under different fertilization treatments the filling duration of W2 was extended by 3-8 days compared with W1, and the grain dry weight was higher 25 days after anthesis. The maximum and average filling rates of T3 and T4 were large, the filling duration was short, and the filling rate in each period was significantly positively correlated with the thousand-grain weight. Under the recommended fertilization level T2, there is a large improvement in the partial productivity of highland barley. When the amount of chemical fertilizer was reduced by 45% and organic fertilizer was applied, the partial productivity of chemical fertilizer increased significantly. The average yield of each fertilization treatment with W2 increased by 7.48% in (2019) and 7.06% in (2020) compared with W1. Under the same irrigation, the yield of T4 was always significantly increased compared with other fertilization treatments. The results show that on the basis of the current recommended fertilization level (T2), reducing chemical fertilizer by 15% to 30%, and applying bio-organic fertilizer by 30% to 60%, the T3 and T4, can significantly increase the grain filling rate of highland barley, shorten the filling duration, and increase yield. It is also the optimized water and fertilizer management mode for highland barley cultivation regions. This study serves as an important reference for the optimal management of N fertilizer with irrigation regimes and the promotion of sustainable agricultural development of highland barley cultivation.