长期水稻-大麦轮作体系土壤供氮能力与作物需氮量研究

通过18年稻麦轮作，7个施肥处理，研究了水稻-大麦轮作系统中土壤生产力、氮素自然供应能力、作物氮素内部利用率及氮肥表观利用率。结果表明，在水旱轮作下，土壤对大麦产量的地力贡献率平均为69%，水稻为75%～81%; 肥料的增产贡献率分别为31%和19%～25%，可维持每年生产大麦2.3 t/hm2、稻谷6～7 t/hm2。土壤氮素自然供给力在大麦上平均为75.9%，比水稻的低3.3%～7.2%。在一年三熟水旱轮作制中，土壤和环境年供氮118～299 kg/hm2; 在一年二熟轮作制中为86～199 kg/hm2。施氮肥条件下，大麦的氮素内部利用率为31.0～56.3 kg/kg; 水稻在23.6～50.2 kg/kg之间变动; 大麦的氮肥利用率变幅在27.5%～41.2%，水稻为14.6%～41.2%。在稻麦轮作系统中，如果想获得作物产量12 t/hm2（4 t大麦和8 t 单季稻），需要每年施氮肥 N 226～337 kg/hm2。为获得更高的作物产量，在氮肥推荐时不但要考虑作物的目标产量，作物对氮素的需要量，还要充分考虑土壤和环境氮素供应能力。

Study on soil nitrogen supplying capacity and nitrogen requirements for crop under long-term rice-barley cropping system

Long-term (over 18 years) rice-barley crop rotation experiment with seven fertilization treatments was conducted to investigate soil natural productivity, indigenous nitrogen (N) supplying capacity, internal N use efficiency and apparent recovery efficiency of N applied. The long-term experimental results indicated the contribution of the soil natural productivity was 68.9% for barley yields and 75%-81% for rice. The contribution of chemical fertilizers increases barley yield by 31% and by 19%-25% for rice. The natural productivity of paddy soil could annual maintain 2.3 t/ha barley and 6-7 t/ha rice grain yields. The soil indigenous N supplying capacity to barley was 75.9%, which was lower 3.3%-7.2% than rice. The amount of soil and environment indigenous N supplying was 118-299 kg/ha for barley-early rice-late rice rotation cropping system and 86-199 kg/ha for barley-rice rotation system. The internal N use efficiency in soils received N fertilizer was 31.0-56.3 kg/kg for barley and 23.6-50.2 kg/kg for rice. The recovery efficiency of N applied were 27.5%-41.2% and 14.6%-41.2% for barley and rice, respectively. To produce 12 t/hm² grains, crops require N 226-337 kg/ha under the rice-barley rotation systems. Our study suggests that in order to achieve higher crop yields, yield targets, soil and environment indigenous N supplying capacity and crop N requirement should be considered when making N fertilizer recommendations and developing strategies for intensively managed rice-barley cropping systems.