长期不均衡施肥对紫色土肥力质量的影响

Effect of long-term imbalanced fertilization on purple soil fertility

利用长期定位试验研究了不均衡施肥对紫色土土壤肥力、肥料利用率和养分平衡状况的影响。结果表明，连续11年不施肥，耕层土壤有机质和全氮含量降低，施用化肥的各个处理土壤有机质和氮素含量稳中有升，其中以NPK均衡施用增幅最大。所有施磷处理，土壤速效磷含量与试验前相比都有大幅度提高；无论施钾与否，土壤缓效钾含量均比试验前降低，稻草还田土壤缓效钾下降最少。不均衡施肥降低了肥料利用率和肥料的增产效果。每季施N 150kg／hm^2，维持了土壤氮素肥力；每季施P2O5 60～75kg／hm^2，磷素都有赢余；除秸秆还田处理钾素有盈余外，其余各处理钾都亏缺。

A long-term field experiment with fixed site was conducted to study the effects of imbalanced fertilization on soil fertility, fertilizer use efficiency and nutrient balance in rice-wheat cropping systems was studied. The results showed that the content of soil organic matter and total nitrogen declined in the treatment without fertilization for 11 years, while it were increased in each treatment with chemical fertilizer application, among which organic matter content for NPK balanced fertilization treatment was the highest. Soil available P content was substantially increased for all treatments with phosphate fertilizer application compared with background value before experiment. Soil slowly available K content was lower than background value before experiment in all treatments whether potash fertilizer was applied or not, among which soil slowly available K was highest with straw returning to the soil. Imbalanced application of N, P and K induced a reduction of crop yield and the efficiency of chemical fertilizer, as well as depletion of soil nutrients. Applying N 150 kg/ha per cropping season could maintain soil nitrogen fertility; Applying P2O5 60-75 kg/ha per cropping season could cause P surplus. Soil potassium was deficient for all treatments except the treatment of straw returning in rice-wheat crop- ping systems.