暗管控制排水棉田NO_3^--N和NH_4^+-N运移转化试验

Experiment of the nitrogen transformation and transportation in controlled pipe-drainage cotton field

为了研究控制排水条件下土壤剖面NH4+-N和NO3--N之间的转化运移规律,2008、2009年在荆州丫角排灌试验站棉花生育期内进行大田暗管控制排水对比试验:2008年全生育期内固定排水出口埋深、2009年分生育阶段调整出口埋深。结果发现:无论调整出口埋深与否,NO3--N含量在土壤垂直剖面上都随土层深度增加而减少。NH4+-N含量2008年随土层深度增加无明显变化规律、2009年在20、40cm处较60、80cm高。控制排水小区表层和20cm土层NO3--N含量较自由排水小区高;同层土控制排水小区NH4+-N含量比自由排水小区高。2008年各处理NO3--N含量高于2009年,NH4+-N含量低于2009年,NO3--N与NH4+-N同层土平均含量之比大于2009年。分生育阶段调整排水出口埋深可减小田间地下水位波动,更能使田间氮素形态稳定、减少氮素流失。

A filed contrastive experiment project was set up at Drainage and Irrigation Experimental Station,Jingzhou Yajiao to study how controlled pipe-drainage influence the N transformation and transportation.The depth of outlet was fixed through the whole growth period in 2008 and adjusted according to different stages in 2009.The results showed that nitrate concentration in the vertical soil profile decreased with the depth increase.Ammonia concentration had no obvious variation with depth in 2008 and was higher in 20,40 cm layers than that in 60,80 cm layers.Nitrate concentration was higher in surface and 20 cm layers in controlled treatments.Ammonia concentration was higher in the same layers in controlled treatments than that in conditional treatment.The ratio between nitrate and ammonia concentration was larger in 2008 than that in 2009.Adjusting the depth of the drainage outlet according to the growth stages could keep the nitrogen content more stable than fixing the depth in the whole growth period,and reduce nitrogen losses.