Abstract:
Organic amendment and chemical fertilizer application are important approaches for improving wheat production, while a suitable replacement ratio of organic nitrogen for chemical fertilizer is essential. This study examined 176 winter wheat yield datasets collected from 33 published articles with chemical fertilization and chemical fertilization combined with organic fertilization treatments. The effect of substituting manure for chemical fertilizer under different fertilization measures and soil properties on yield of winter wheat was quantified by meta-analysis, and the appropriate rate of organic N substitution (RS) was explored. In general, the yield increases significantly by 5.0% - 7.4% when RS is 10% - 50%, but declines significantly by 8.0% when RS is over 90%. When RS is 10% - 20% with nitrogen rate≤150 kg·hm
−2, yield increases by 7.5%. When RS is 30% - 40% with nitrogen rate of 150 - 250 kg·hm
−2, yield increases by 7.7%. When RS is less than 50% with nitrogen rate >250 kg·hm
−2, yield increases by 6.3% - 10.3%. At low soil nutrient content levels (organic matter content ≤15 g·kg
−1, total nitrogen content ≤1 g·kg
−1, available phosphorus content ≤40 mg·kg
−1, available potassium content 50 - 150 mg·kg
−1), the optimal RS is 10% - 20% with yield gain of 7.3% - 9.8%. At medium-high nutrient content levels (soil organic matter content >25 g·kg
−1, available potassium content >150 mg·kg
−1), the optimal RS should be less than 50% with yield gain of 5.3% ~ 10.6%. The main factors affecting winter wheat yield increase are RS and fertilizer resource (importance >15%), followed by available potassium, SOM, N input (importance >10%). Therefore, preferred RS is 10% - 20% when soil’s nutrient content is low, less than 50% when soil organic matter content is >25 g·kg
−1, available potassium content is >150 mg·kg
−1. The preferred RS is 10% - 20% for nitrogen rate of <150 kg·hm
−2, 30% - 40% for nitrogen rate of 150 - 250 kg·hm
−2, and less than 50% for nitrogen rate of >250 kg·hm
−2. Bio-organic fertilizer, chicken manure and pig manure are recommended to replace chemical fertilizer.