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

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.