不同施肥及杂草处理下半湿润冬小麦田NO3^-N的动态变化

Dynamic changes of soil NO_3^--N as affected by different N fertilizer application and weed treatments in semi-humid winter wheat field

以中等肥力土垫旱耕人为土为供试土壤,在冬小麦(Triticumaestivum)不同生育期采集0—100 cm土层土壤样品,研究不同施肥及杂草处理对半湿润农田生态系统土壤NO3--N动态变化的影响。结果表明,1)土壤剖面NO3--N含量随施氮量增加而显著增加,0—100 cm土层NO3--N累积量与施氮量线性相关;在越冬期、返青期和拔节期,相关系数r分别为0.995、0.971和0.949。2)冬小麦生长过程中,土体NO3--N含量先降低后回升,在拔节期最低;成熟期土壤有机氮矿化产生的NO3--N是收获后土壤剖面残留NO3--N的主要贡献者。3)在越冬期、返青期、拔节期和成熟期,施磷(PN135)与不施磷(P0N135)处理相比,施磷可显著减少土体NO3--N累积量,减少量分别为N61.4、26.9、36.6和5.5 kg/hm2;磷肥对土壤NO3--N残留累积量的削减效应以越冬期表现最为显著,成熟期表现不显著。4)在施磷的基础上,不同杂草处理土壤剖面NO3--N累积量在施氮量为45 kg/hm2(PN45)及90 kg/hm2(PN90)时差异不显著;而在施氮量为180 kg/hm2(即PN180)的高氮处理下差异显著。每公顷施氮135 kg(PN135)的中氮处理,在越冬期清除杂草后土壤剖面中NO3--N累积量在拔节期显著高于其它杂草处理。

Application of nitrogen （N） fertilizer is one of the most important measures to increase grain yield and improve grain quality of winter wheat. However, it is common that excessive N fertilizer is applied in fertile field, which results in higher amount of nitrate （NO3^--N） accumulation in the soil, bringing potential risks to the environment. Nitrogen （N） application strategies were evaluated to determine the extent to which these treatments could reduce nitrate （NO3^--N） leaching. With normal density treatments, six fertilizer treatments （P0N0, PN0, PN45, PN90, PN135 and PN180） were applied, and with lower density treatments, four levels of fertilizer P0N0, PN0, PN135 and P0N135 were applied. Within each of these treatment combinations, different weed treatments were imposed. This experiment was carried out in Eum- Orthic Anthrosol located in the semi-humid farmland ecological system. Soil samples of 0-100 cm layer were collected during different growth stages of winter wheat to study the dynamic changes of NO3^--N as affected by different fertilizer and weed treatments in semi-humid winter wheat（ Tritcum aestivum）field. The results showed that NO3^--N accumulation in soil profile remarkably increased with N application rate, and NO3^--N accumulation of 0-100 cm soil profile was linearly related with N rate. The correlation coefficients at over-wintering, regreening and jointing stage were 0.995, 0.971 and 0.949, respectively. 2） During the whole growth stage of winter wheat, soil NO3^--N content decreased first, and then increased. NO3^--N content at jointing stage was the lowest. NO3^--N resulted from organic nitrogen mineralization at maturity was a major contributor to soil residual NO3^--N after harvesting. 3） During over-winter, regreening, jointing stage and after harvest, NO3^--N of P application （PN135） was reduced by N 61.4（ P 〈 0.05）, 26.9（ P 〈 0.05）, 36.6（ P 〈 0.05） and 5.5 kg/ha, compared with P0N135. 4） In different weed treatments of low level N （PN45, PN90）, NO3^--N accumulation was not significantly different, but there was significant difference at high level N （PN180） （ P 〈 0.05 ） among different weed treatments. After removing weeds in the over-winter stage, the NO3^--N content of PN135 was remarkably higher than other weed treatments at jointing stage.