关键词: 氮肥, 磷肥, 羊草割草场, 土壤养分

Abstract: [Objective] To investigate the effects of combinative application of nitrogen （N） and phosphorus （P） fertilizers based on improvement by root cutting on soil nutrient of Leymus chinensis mowing meadow in Horqin grassland. [Method] On the basis of root cutting, a field experiment of adding N and P fertilizers at different concentrations was conducted in the Leymus chinensis mowing meadow. Using a randomized block design, four treatment levels of N and P fertilizers, including CK （control）, NP1 （urea 75 kg/hm²+diammonium phosphate 45 kg/hm²）, NP2 （urea 150 kg/hm²+diammonium phosphate 90 kg/hm²）, and NP3 （urea 225 kg/hm²+diammonium phosphate 135 kg/hm²), were set. There were 3 blocks as repeats for each treatment, and there was a total of 12 experimental plots. In mid-August 2014, a 1 m × 1 m quadrat was randomly set in each plot, and the soil samples were collected after cutting the plant samples at 0 cm stubble; three sampling points were randomly chosen, and the contents of soil N, P and potassium （K） as well as soil organic matter were determined by Kjeldahl method, alkaline hydrolysis method, molybdenum-antimony anti-colorimetric method, acid dissolution-molybdenum-antimony anti-colorimetric method, sodium hydroxide fusion method, ammonium acetate extraction-flame photometric method, and potassium dichromate titrimetric method.[Result] Compared with CK, NP3 treatment induced the significant （P<0.05） reduction of total N content in 10-20 cm soil layer; the 3 fertilization treatments significantly （P<0.05） increased the available N content in 0-10 cm and 10-20 cm soil layers; NP3 treatment significantly （P<0.05） increased the contents of total P and available P in 0-10 cm soil layer, and NP2 treatment significantly （P<0.05） increased the available P contents in 0-10 cm and 20-30 cm soil layers; NP2 and NP3 treatments induced the significant （P<0.05） reduction of total K contents in 10-20 cm and 20-30 cm soil layers, and NP3 treatment induced the significant （P<0.05） reduction of available K content in 0-10 cm soil layer; the 3 fertilization treatments significantly （P<0.05） increased the organic matter contents in different soil layers.[Conclusion] Considering the changes in soil nutrient contents after applying N and P fertilizers, a combinative application of K fertilizer at a certain level is necessary to improve the soil nutrient status of the Leymus chinensis mowing meadow in Horqin grassland.

Key words: nitrogen fertilization, phosphorus fertilizer, Leymus chinensis mowing meadow, soil nutrient