Effects of organic substitution on the yield and nutrient absorption and utilization of wheat under chemical fertilizer reduction

Objectives The yield and nutrient effects of simultaneous chemical fertilizer reduction and manure substitution were studied, in order to provide a theoretical basis for the national zero growth strategy of chemical fertilizer.

Methods A localized field experiment was conducted for two consecutively wheat seasons during 2017–2019 in Shanxi Province. The conventional fertilization rate was used as control (CF), reducing 25% N, 30% P₂O₅ and 16.7% K₂O as fertilizer reduction treatment (CFR), organic substitution treatments were designed as conventional fertilizer one (CF+M, 30% N substituted by chicken manure) and reduced fertilizer one (CFR+M, 30% N substituted by chicken manure), and complete chicken manure in reduced N input level (M) was setup at the same time. Wheat yield and its components, biomass, wheat plant dry matter and N, P, K accumulation at different growth stages were investigated.

Results The yield components were not significantly affected by the fertilization treatments on average. Compared with CF, the yields in treatments CFR and CF+M were not significantly different, but those in treatments of CFR+M and M were significantly decreased. There was no significant difference in N and K absorption between CF+M and CF in each growth stage, especially after jointing stage. Compared with CF, CFR and CF+M decreased N, P translocation of stem and leaf before anthesis and N, P accumulation after anthesis, but there was no significant difference among the three treatments. Compared with CF, CF+M increased contribution proportion of N, P translocation of stem and leaf before anthesis and N, P accumulation after anthesis to grain. There was a significant or extremely significant positive correlation between grain N accumulation and N accumulation at different growth stages, N translocation from stem and leaf before anthesis and N accumulation after anthesis. P accumulation in grains only had significant positive correlation with P accumulation after anthesis. The accumulation of K in grains had significant positive correlation with the accumulation of K between re-greening stage and jointing stage, and a significant negative correlation with the accumulation and the translocation of K in spikelet and rachis before anthesis. Compared with CF, CFR and CF+M improved the absorption efficiency, utilization efficiency and production efficiency of N, P, utilization efficiency of K, and reduced the absorption efficiency and partial factor productivity of K.

Conclusions Duringthe experiment years, the reduction of chemical fertilizer or replacing 30% of N with chicken manure without reducing the total fertilizer input has not show adverse impaction on wheat yield and nutrient efficiency. While replacing 30% or 100% of N with chicken manure under reduced fertilizer input has showed significant decrease effect on wheat yield, in spite of the increased nutrient transport and use efficiencies. The proper reduction ratio of nitrogen fertilizer that used in organic replacement needs further study in a long run in Shanxi Province.