施氮对不同栽培模式旱地土壤有机碳氮和供氮能力的影响

Effects of nitrogen fertilizer application on soil organic carbon and nitrogen accumulation and mineralization under different cultivations in northwest dryland

【目的】研究不同栽培模式下,施氮量对西北旱地土壤有机碳氮累积及供氮能力的影响。【方法】通过5年(2002-2007年)定位大田试验,以不施氮为对照,比较不同施氮量(120,240kg/hm2)对常规、覆草和覆膜3种栽培模式土壤有机碳氮累积和供氮能力的影响。【结果】施氮0,120,240kg/hm2时,覆草栽培土壤有机碳含量分别为9.74,9.57,9.19g/kg,全氮含量为0.99,1.02,1.03g/kg,土壤氮素矿化势为25.0,26.7,29.7mg/kg,矿化速率常数为0.053,0.062,0.056/d;覆膜栽培土壤有机碳含量分别为9.82,8.78,9.80g/kg,全氮含量为0.98,0.98,0.95g/kg,土壤氮素矿化势为23.2,25.8,24.1mg/kg,矿化速率常数为0.058,0.061,0.072/d;常规栽培土壤有机碳含量分别为9.79,9.93,9.20g/kg,全氮含量为0.93,0.99,0.96g/kg,土壤氮素矿化势为23.2,26.2,25.7mg/kg,矿化速率常数为0.057,0.061,0.063/d。【结论】施氮能提高3个栽培模式土壤的供氮能力,促进土壤氮素的矿化。适量氮肥能够提高常规模式土壤的有机碳含量,但会降低覆草和覆膜土壤的有机碳含量,故在采用地表覆盖模式栽培时需配施有机肥。

[Objective] Effects of nitrogen application rates on organic carbon and nitrogen accumulation and mineralization in dryland soil were investigated in this paper. [Method] Using soils from a 5-year long nitrogen fertilizer experiment with fixed blocks in Yangling,Shaanxi, we conducted an indoor incubation experiment to study the effects of nitrogen fertilizer rates on organic carbon and nitrogen accumulation and mineralization at 0,120,240 kg N/hm^2 under three cultivations as straw mulch,plastic-film mulch and no-mulch. [Result] Under the three nitrogen application rates of 0,120,240 kg/hm^2, soil organic carbon contents under straw mulch were 9.74,9.57,9.19 g/kg, total soil nitrogen contents 0. 99 ,1. 02 ,1. 03 g/kg, soil nitrogen mineralization potential 25. 0,26. 7,29. 7 mg/kg, and nitrogen mineralization rates 0. 053, 0. 062,0. 056 /d. Correspondingly, contents of soil organic carbon under plastic-film mulch were 9.82, 8.78,9.80 g/kg, total soil nitrogen contents 0. 98,0. 98,0. 95 g/kg, soil nitrogen mineralization potential 23.2,25.8,24.1 mg/kg, and nitrogen mineralized rates 0. 058,0. 061,0. 072 /d. Under conventional cultivation （no-mulch）, soil organic carbon contents were 9.79,9.93,9.20 g/kg, soil total nitrogen contents 0. 93,0. 99,0. 96 g/kg, soil nitrogen mineralization potential 23.2,26.2,25.7 mg/kg, nitrogen mineraliza- tion rates 0. 057,0. 061,0. 063/d. [Conclusion] Nitrogen application could improve organic nitrogen mineralization potential and rates of soils from three cultivations. Proper amount of nitrogen fertilizer could increase organic carbon content of the no-mulch soil, but decrease the straw mulch and plastic-film soil. Both cultivation models of straw mulch and plastic-film mulch need to apply organic fertilizer when nitrogen fertilizer is applied.