Effect of long-term fertilizer application on yield, nitrogen uptake and soil NO3--N accumulation in wheat/maize intercropping

After 14 years long-term fertilization, NO~-_3-N accumulation in soil profile, nitrogen uptake and utilization by intercropped wheat and maize was investigated. The results showed that among manure120 t/hm22(M),green manure 45 t/hm2(G),straw 10.5 t/hm2(S), N375 kg/hm2(N), manure 60 t/hm2+ N187.5 (kg/hm2), green manure 22.5 t/hm2+ N187.5kg/hm2, straw 5.25 t/hm2+ N187.5 kg/hm2and CK treatments,soil NO3--N concentration and accumulation was the highest with N 375 km/hm2 application, above-ground nitrogen concentration and nitrogen uptake were higher with N, 1/2(M+N) and 1/2(G+N) treatments, but among three treatments existed no significant difference. Grain yields and biomass of intercropped wheat were higher with M,G,1/2(M+N) and 1/2(G+N) treatments, and intercropped maize were higher with 1/2(G+N), N, M and 1/2(M+N) treatments. Nitrogen use efficiency was the highest with 1/2(S+N) treatment, 1/2(M+N) and 1/2(G+N) treatment were lower than 1/2(S+N),S and N treatments,but were higher than that of M and G treatments. It suggested that nitrogen fertilizer combined with organic matter could increase grain yields, enhance nitrogen concentration and uptake, reduce nitrate accumulation in soils.