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在京郊露地生产条件下,研究不同供N处理对秋季大白菜的生长、N吸收和土壤N矿化及损失的影响,并根据土壤-作物系统中N的“借贷”平衡原理确定大白菜N供应的合理目标值。结果表明,大白菜的产量和N吸收随施N水平的增加呈线性-平台的增长趋势。在作物的目标产量(120t/hm2)和N吸收数量(N200kg/hm2)的情况下,适宜的N素供应水平,即目标值为N350kg/hm2。大白菜的N吸收量随生育期逐渐增加,包心前期平均每周的N吸收量为N8 5kg/hm2,而在包心后期达到N22 0kg/hm2。在作物的整个生育期间土壤N的净矿化数量为N37kg/hm2,平均每周的土壤表观N损失为N7 8kg/hm2。这些参数有助于利用简单的N“借贷”平衡指导京郊秋季大白菜的推荐施肥。
Under open field conditions in Beijing suburbs, the effects of different N treatments on the growth, N uptake and N mineralization and soil loss of autumn Chinese cabbage were studied and the results were determined according to the equilibrium principle of N in the soil-crop system Cabbage N supply a reasonable target value. The results showed that the yield and N uptake of Chinese cabbage showed a linear-platform increasing trend with the increase of N application rate. In the case of crop target production (120t / hm2) and N uptake (N200kg / hm2), the appropriate N supply level, ie target value N350kg / hm2. The N uptake of Chinese cabbage gradually increased with the growth period, and the average N uptake per week of early pericarp was N8 5kg / hm2, while it reached N22 0kg / hm2 in late stage of pericardium. Net mineralization of soil N was N37 kg / hm2 throughout the crop’s entire reproductive period, with an average weekly apparent soil N loss of N7 8 kg / hm2. These parameters help to guide the recommended fertilization of autumn Chinese cabbage in the suburbs of Beijing using a simple N “lending ” balance.