制种玉米连作恒量施磷对灌漠土与潮土中磷素利用的影响

目的]研究恒量外源磷施用对玉米种子生产的影响,为合理施磷提供依据。方法]通过大田定位与实验室分析相结合,选用河西走廊石灰性潮土及灌漠土定位施肥。结果]制种玉米连作8a,恒量磷二铵525kg/(hm^2·a)施用,除无机态二钙磷(Ca_2-P)外,2种不同土类总磷(T-P)、速效性磷(Av-P)、总无机磷(T-IP)、总有机磷(T-OP),以及其他各分级无机、有机磷组分均显著增加。无机磷占全磷总量65.2%~70.2%,有机磷占全磷总量6.5%~11.4%。无机磷中十钙磷(Ca₁₀-P)>八钙磷(Ca8-P)>铝磷(Al-P)>铁磷(Fe-P)>闭蓄态磷(O-P)。有机磷中活性有机磷(MLO-P)>高稳性(HRO-P)>中稳性有机磷(MROP)>活性有机磷(LO-P)。随连作年限增加,灌漠土Ca₁₀-P在连作第5a达到最大,Al-P,O-P均持续增加;潮土Ca₁₀-P持续增加,Fe-P,O-P在连作第5a达到最大,磷增加量为3.94%~37.28%。0—60cm土层,两种土类无机磷各组分含量均呈现由表层至下层递减特点,但不同分级磷在不同土层所占比例不同,Ca₁₀-P,Al-P,O-P,MRO-P底聚,Ca_2-P,HRO-P表聚,制种玉米连作生产8a,磷肥最大表观利用率为4.89%,磷素活化系数<2%,外源磷肥以174.3kg/(hm^2·a)残余在土壤中。结论]制种玉米连作,总磷转化率低,磷素移动缓慢,大部分以溶解性较低的磷素形态在土壤表层积累,但随连作年限增加,土壤对磷素的固持及转化率下降,表现底聚趋势,对生态环境健康存在极大风险,应减量或停止施磷。潮土磷肥施用应采取更加合理措施。

Effects of Constant Phosphorus Fertilization and Continuous Cropping of Corn Seed on Phosphorus Utilization of Irrigated Desert Soil and Alluvial Soil

Objective] The effects of constant phosphorus fertilization on corn seed production were studied to provide the basis for reasonable phosphorus fertilizer application.Methods] Field experiments and laboratory analysis were conducted in irrigated desert soil and alluvial soil.Results] Except for Ca₂-P, total phosphorus, available phosphorus, total inorganic phosphorus, total organic phosphorus, and the other fractions of inorganic and organic phosphorus increased significantly under 8 years continuous cropping of corn seed with 525 kg/(hm²·a) of chemical phosphorus fertilizer. The inorganic phosphorus amounted to 65.2%~70.2% of total phosphorus, while organic phosphorus accounted for 6.5%~11.4%. Ca₁₀-P > Ca₈-P > Al-P > Fe-P > O-P. MLO-P > HRO-P > MRO-P > LO-P. Ca₁₀-P reached to the highest at 5th year, and Al-P and O-P increased constantly in irrigated desert soil. Ca₁₀-P increased constantly while Al-P and O-P reached to the highest at 5th year in alluvial soil. The phosphorus increased by 3.94%~37.38%. Inorganic phosphorus declined from soil surface downward to a depth of 60 cm. The proportion of different fraction varied in different soil layers. Ca₁₀-P, O-P, Al-P and MRO-P was gathered in soil layer of 40-60 cm while Ca₂-P and HRO-P gathered in soil layer of 0-20 cm. The highest apparent efficiency of phosphorus fertilizer was 4.89% and phosphorus active coefficient was lower than 2% after 8 years continuous cropping. And the residual of exogenous phosphorus was 174.3 kg/(hm²·a) which means the lower conversion ratio of total phosphorus.Conclusion] The movement of phosphorus was slow in two soils and accumulated with lower soluble fractions in surface soil layer with continuous cropping. The proportion of attachment and retention and the transportation of phosphorus by soil decreased constantly and possibly gathered toward bottom layer, which will cause high ecological risks on healthy development of ecological environment. Phosphorus fertilizer should be decreased or stop to use, also some suitable methods should be used for phosphorus utilization on alluvial soil.