滴灌灌水量对风沙土大豆根区硝态氮及水分分布的影响

Effects of drip irrigation amounts on nitrate-N and water distribution in the root zone of soybean in a wind-sandy soil

为合理进行风沙土地区灌溉管理,将水肥控制在根区范围内并满足大豆生长需求,以灌水量为试验因素,基于作物冠层蒸发皿蒸发量设置0.4(W1)、0.6(W2)、0.8(W3)、1.0 E_(pan)(W4)和1.2 E_(pan)(W5)5个灌溉水平,研究不同灌水量对大豆根区硝态氮和水分分布的影响。结果表明:增加灌水量会使土壤水分入渗深度增加10~30 cm,增大根区土壤水分分布的不均匀性,苗期W5处理剖面水分平均值较W1处理增大40.22%,W4、W5处理能够维持大豆根区6%~7%的土壤含水率。硝态氮有明显表聚现象,随着灌水量的增大,淋洗深度增加且不均匀性增大,根区土壤硝态氮平均含量降低,当灌水量高于1.0 E_(pan)时,硝态氮含量低于10 mg·kg^(-1)。W2、W3和W4处理能保证大豆根区在生育前、中、后期处于15~22 mg·kg^(-1)的硝态氮浓度区间,垂直方向上灌水量与硝态氮呈负相关关系。风沙土土壤剖面含水率均在4%~10%之间,灌水量是影响风沙土硝态氮含量和分布的主要因素之一;各处理硝态氮含量在10~30 mg·kg^(-1)之间。综合考虑作物对根区土壤水分和硝态氮含量的需求,以及土壤水分和硝态氮在根层的分布特征,推荐灌溉水量为1.0 E_(pan)。

The objective of this study was to examine the effects of controlling water and fertilizer inside the root zone and at the same time,meeting soybean development requirements by more logically managing irrigation in wind-sandy soil environment.Based on the evapotranspiration of the crop canopy at five irrigation levels of 0.4(W1),0.6(W2),0.8(W3),1.0(W4),and 1.2 E_(pan)(W5),a field experiment was carried out to examine the effects of different irrigation levels on nitrate-N and water distribution in the root zone of soybean.Increasing the irrigation volume resulted in increase of the depth of soil moisture infiltration by 10~30 cm,increasing the uneven distribution of soil moisture in the root zone.The average water content of the W5 treatment profile during the seedling stage increased by 40.22%compared to the W1 treatment.The W4 and W5 treatments were able to maintain a soil moisture content of 6%to 7%in the soybean root zone.The nitrate-N exhibited a clear epimerization phenomenon.As irrigation volume increased,so did the depth of drenching,inhomogeneity,and average nitrate-N content of the root zone soil decreased.When irrigation volume exceeded 1.0 E_(pan),nitrate-N was lower than 10 mg·kg^(-1).In the pre-fertility,mid-fertility,and late-fertility periods,the nitrate-N concentration interval of the soybean root zone was satisfied by the W2,W3,and W4 treatments,which were in the range of 15~22 mg·kg^(-1).The irrigation volume had a stronger negative vertical correlation with the nitrate-N content of the soybean root zone.The soil profile moisture content of wind-sandy soil was between 4%and 10%,and the amount of irrigation was one of the primary parameters influencing the distribution and nitrate-N content of wind-sandy soil;the nitrate-N content of each treatment varied between 10 mg·kg^(-1) and 30 mg·kg^(-1).The recommended irrigation water amount was 1.0 E_(pan),considering the crop’s requirements for soil water and nitrate-N content in the root zone,as well as the features of soil water and nitrate-N distribution in the root layer.