Effect of Different Irrigation Methods on Soil Organic Matter and Nitrogen Forms in Protected Field

The effects of different irrigation methods(subsurface irrigation,drip irrigation and furrow irrigation) on soil N forms and its profile distribution were studied in a protected field by determining the content of soil organic matter,total N,inorganic N and soil organic N.The same irrigation experiment was conducted for seven years and soils were sampled at different depths within 0-80cm.The result showed that soil organic matter changed from 8.47 to 36.48 g kg-1.The change of soil organic matter in soil profile was similar in subsurface irrigation and drip irrigation,however,great difference was found in furrow irrigation compared with other irrigation methods in 0-80cm soil layer.The content of soil organic matter in furrow irrigation was higher than that in subsurface irrigation and drip irrigation except at the depth of 30-40 cm.There are significant differences in soil total N and inorganic N at the depth of 0-20 cm with the highest content in subsurface irrigation,furrow irrigation secondly and drip irrigation thirdly.Soil total N,NO3——N,NH4+-N and organic N changed from 0.72 to 3.97 g kg-1,19.16 to 1442.06 mg kg-1,0 to 15.28 mg kg-1 and 683.79 to 2512.87 mg kg-1 respectively.Soil organic N was the highest in subsurface irrigation at the depth of 0-10 cm,the furrow irrigation was the next,and the drip irrigation was the last.But soil organic N was the highest in furrow irrigation at the depth of 10-30.