密度与氮量对复种油菜土壤肥力性状的影响

通过田间小区试验,研究了不同油菜种植密度与施氮肥对麦茬复种油菜苗期和收获期耕层土壤(0~15cm)肥力性状的影响.结果表明,复种饲料油菜能明显提高耕层土壤有机质、速效钾、碱解氮、速效磷、有机碳(OC)和易氧化有机碳(ROOC)质量分数以及氮利用效率,而土壤稳定性有机碳(SOC)质量分数与有机碳氧化稳定系数(K_(os))明显降低.在油菜苗期,随种植密度提高,土壤有机质先增后减,全氮不断减少,氮效率以及碱解氮、全磷、速效磷质量分数逐渐提高,随增施氮肥水平提高,土壤有机质、全氮、全磷和碱解氮质量分数均不断提高,氮效率与速效磷质量分数不断减少;在收获期,随种植密度提高,土壤有机质先增后减,全氮、全磷不断减少,碱解氮、速效磷和氮效率不断增加,随增施氮肥水平提高,土壤有机质、全氮、全磷、碱解氮和速效磷质量分数逐渐提高,氮效率却不断降低,差异分析均无统计学意义.随种植密度和施氮肥水平提高,耕层土壤中OC,ROOC和ROOC百分比均不断提高,而SOC,SOC百分比和K_(os)均逐渐降低,差异分析均有统计学意义.耕层土壤OC和K_(os)分别与有机质、碱解氮、速效磷、速效钾呈明显的正相关性和负相关性(p0.05或p0.01),表明土壤OC和K_(os)可作为土壤有效养分利用潜力的表征指标.

Effect of Planting Density and Nitrogen Fertilizer on Soil Fertility Properties with Wheat/Forage Rape Multiple Cropping

A field experiment was conducted in Lanzhou, China to study the effects of rape planting density and nitrogen fertilizer rate on the soil fertility properties of the topsoil (0~15 cm) of wheat stubble multiple cropping rape. The results showed that topsoil soil organic matter, available K, alkali-hydrozable N, available P, organic carbon (OC), readily oxidizable organic carbon (ROOC) content and N utilization efficiency increased significantly and soil stability organic carbon (SOC) content and oxidation stability coefficient (Kos) decreased significantly by planting rape after wheat, which suggested that the plant pattern of wheat/forage rape multiple cropping could improve soil fertility of cropland. During the seedling stage of the rape crop, soil organic matter first increased, followed then by a decline, total N decreased steadily, and N utilization efficiency, alkali-hydrozable N, total P and available P increased gradually with the increase in planting density; soil organic matter, total N, total P and alkali-hydrozable N content in the topsoil were enhanced but N utilization efficiency and available P decreased continuously with increasing nitrogen rates. During the harvest stage of rape, soil organic matter first increased and then decreased, total N and total P steadily decreased in the topsoil, while alkali-hydrozable N, available P and N utilization efficiency increased continuously with increasing planting density; soil organic matter, total N, total P, alkali-hydrozable N and available P content gradually increased, but N utilization efficiency dropped continuously with increasing nitrogen rates, though the difference was non-significant statistically. Throughout the growth stages of the rape plants, soil OC, ROOC and ROOC percent all increased gradually while SOC, SOC percent and Kos decreased continuously, and the difference was highly significant statistically (p < 0.05, PLSD). Soil OC on the topsoil and soil Kos were in highly significant positive and negative correlation, respectively, with soil organic matter, alkali-hydrozable N, available P and available K, indicating that soil OC and Kos can be used as indicators for characterization of the utilization potential of soil available nutrients.