滴灌均匀系数对土壤水分和氮素分布的影响

Field evaluation of drip fertigation uniformity effects on distributions of water and nitrogen in soil

为了确定滴灌均匀系数的设计与评价标准,在日光温室内研究了滴灌施肥灌溉均匀性和施氮量对土壤水氮分布特性的影响。试验中滴灌均匀系数(Cu)设置0.62、0.80和0.963个水平,施氮量设置150和300kg/hm22个水平。土壤含水率和电导率采用沿毛管均匀布置的TDR探头(Hydra Probe)连续监测,并定期取土样测试土壤硝态氮和铵态氮含量。结果表明,在作物生育期内3种滴灌均匀系数处理的土壤含水率一直保持很高的均匀系数,滴灌均匀系数和施氮量对土壤含水率均值及其均匀系数的影响均不显著(α=0.05)。土壤电导率及硝态氮含量的均匀性在很大程度上取决于土壤初始氮素含量的均匀性,其均匀系数低于土壤含水率的均匀系数,滴灌均匀系数的影响也不显著。从获得均匀的土壤水氮分布的角度出发,现行滴灌均匀系数标准尚有降低的空间。

The effects of drip fertigation uniformity and nitrogen applied on the distributions of water and nitrate in soil were investigated in a solar heated greenhouse in the growing season of Chinese cabbage to determine the design and evaluation standards of drip irrigation uniformity. Three Christiansen uniformity coefficients of 0.62,0.80 and 0.96 and two levels of nitrogen applied at 150 and 300 kg/hm2 were used. The distributions of soil water content and bulk electrical conductivity were monitored continuously by equally spaced TDR sensors （Hydra Probe） along a dripline. Gravimetric samples of soil around each TDR sensor were collected regularly to determine the distributions of nitrate and ammonium nitrogen contents. A substantially high uniformity coefficient of soil water content was observed during the whole growing season for all three fertigation uniformity tests. The effects of fertigation uniformity and nitrogen applied on the mean and the uniformity of water in soil were insignificant at a significance level of 0.05. The uniformity coefficient of soil bulk electrical conductivity and nitrate in soil was substantially lower than that of soil water content,being greatly dependent upon the nonuniformity of initial nitrogen contents in the soil. An insignificant influence of fertigation uniformity on the uniformity of soil bulk electrical conductivity and nitrate content in soil was also observed. It was supported by this study that lower uniformity values of drip irrigation system than those recommended by the current standards could be used if the system mainly aimed at producing a uniform distributions of water and nitrogen in the soil.