不同施肥与耕作对紫色土坡耕地土壤侵蚀及氮素流失的影响

【目的】研究重庆紫色土坡耕地“冬小麦-夏玉米”种植模式在不同施肥制度和耕作模式下由降雨而引发的水土流失特征及氮素流失规律，可为该区农业生产及生态环境保护提供科学依据。【方法】设置4种施肥制度（顺坡耕作对照、顺坡耕作农家肥和化肥配合施用、顺坡耕作单施化肥、顺坡耕作单施化肥增量）和2种耕作模式（顺坡耕作单施化肥、横坡垄作单施化肥），采用野外径流小区长期（2008—2012）定位监测，研究施肥与耕作对坡面土壤侵蚀及氮素流失的影响。【结果】不同施肥制度和不同耕作模式间产流量、产沙量、氮素流失量差异均显著，不施肥处理产流量、产沙量及氮素流失量均最大，施肥、横坡垄作均能有效降低坡面产流产沙及氮素流失量。与相同施肥水平的顺坡耕作相比，横坡耕作分别减少产流量、产沙量、全氮流失量25.9%、20.5%和33.4%，与相同耕作方式的对照相比，农家肥和化肥配合施用可分别减少产流量、产沙量和全氮流失量35.7%、40.5%和41.2%。紫色土区年降雨量与年产流产沙量均呈幂函数关系（y=ax^b，a＞0，b＞0），氮素流失量与径流量呈线性关系（y=ax+b，a>0），但与降雨量相关性不显著，旱坡地氮素流失以总可消化养分（total digestible nutrients，TDN）为主，占全氮的62.1%。农家肥和化肥配合施用可以降低总可消化养分（TDN）和铵态氮（NH₄⁺-N）占全氮的比例。【结论】紫色土区不宜采取顺坡耕作和不施用任何肥料的土地管理方式。农家肥和化肥配合施用、横坡垄作是防治重庆紫色坡面水土流失及径流氮素流失的有效途径，径流中氮素流失以总可消化养分为主。

Effects of Combined Foliar Zn Application with N or P Under Different Water and Nitrogen Managements on Zn Nutritional Quality of Winter Wheat

【Objective】To alleviate the Zn deficiency problems in human population, a field experiment was conducted to investigate the effect of foliar Zn combined with N or P on grain Zn nutritional quality of wheat under different soil water managements and soil N application rates. 【Method】 The experiment was conducted in Guan-zhong Plain with a split-split plot design. The main plot treatments were three soil water management treatments: conventional planting, plastic film mulching (ridge mulching with film and furrow planting with winter wheat), and supplemental irrigation (40 mm irrigation during the over-wintering stage). And the sub-plot treatments were three N application treatments: 0, 120 and 240 kg N·hm^-2. The sub-sub-plot treatments were: CK (distilled water), foliar Zn (0.3% ZnSO₄·7H₂O), foliar Zn+N (0.3% ZnSO₄·7H₂O+1.7% CO(NH₂)₂), foliar Zn+P (0.3% ZnSO₄·7H₂O+0.2% KH₂PO₄). Grain samples were analyzed for Zn, P, and protein concentrations. 【Result】 The obtained results showed that compared to conventional planting, supplemental irrigation significantly increased grain Zn concentration, but film mulching significantly decreased grain Zn concentration in 2011-2012; Grain P/Zn molar ratio was significantly decreased by supplementary irrigation (6.8%) in 2011-2012. Compared to N0 treatment, grain Zn concentration was significantly increased by the N120 and N240 treatments in 2010-2011, with an average of 2.3% and 7.4%, respectively. Besides, N120 and N240 significantly decreased grain P/Zn molar ratio, and the decrement was higher in N240 than in N120, which resulted in a significantly decreased grain P/Zn molar ratio by 33.0% in 2010-2011 and 25.5% in 2011-2012 when compared to the N0 treatment. Furthermore, N fertilizer application resulted in a significant increase in grain protein concentration, but a significant reduction in grain P concentration. Compared with the CK treatment, foliar Zn, foliar Zn+N, and foliar Zn+P treatments significantly increased grain Zn concentrations from 20.6 mg·kg^-1 to 40.3, 39.6 and 33.7 mg·kg^-1, with an average extent of 95.5%, 96.0%, and 63.5%, respectively. These results suggest that combined foliar application of Zn with N or P fertilizers are the efficient agronomic approaches to increase grain Zn concentrations. Meanwhile, the increase in grain Zn concentration in the foliar Zn+N treatment was 5.9 mg·kg^-1 higher than in the foliar Zn+P treatment. Foliar Zn, foliar Zn+N, and foliar Zn+P significantly reduced P/Zn molar ratio by an average of 48.0%, 47.5% and 38.5%, respectively. Foliar Zn application significantly decreased P/Zn molar ratio by 66.7% in 240 kg N·hm^-2 and supplemental irrigation treatment. Grain protein concentration was significantly enhanced by foliar Zn+N treatment, with an average of 5.4% in 2010-2011 and 11.2% in 2011-2012. The foliar fertilizer application induced grain Zn accumulation was maximized by N fertilizer application and supplemental irrigation. When compared to the control treatment (foliar spraying distilled water, 0 kg N·hm^-2, and conventional planting), the foliar Zn+N with 120 kg N·hm^-2 and supplemental irrigation treatment caused the highest increase in grain Zn concentration (110.1%), and the largest decrease in grain P/Zn molar ratio (64.5%). 【Conclusion】Optimal water management practice (supplemental irrigation) and N fertilizer application promoted grain Zn accumulation and increased grain Zn bioavailability in the potentially Zn deficient soils, but there was highly significant increase in grain Zn concentration and bioavailability in the foliar Zn combined with N or P application treatments. And the increase in grain Zn nutritional quality was higher when foliar Zn combined with N than foliar Zn combined with P. Based on the economic benefit and Zn nutritional quality, timely irrigation, moderate N application and foliar Zn combined with N will be an effective method to improve grain Zn nutritional quality of wheat grain, which has a bright promoting prospect in the regions with potentially Zn-deficient or Zn deficient soils.