甘蔗//大豆间作和减量施氮对甘蔗产量、植株及土壤氮素的影响

Effect of sugarcane//soybean intercropping and reduced nitrogen rates on sugarcane yield,plant and soil nitrogen

通过田间试验探讨了甘蔗//大豆1∶1、1∶2间作模式和施氮(300 kg/hm2,525 kg/hm2)水平对甘蔗鲜重产量、甘蔗单株氮含量、土壤硝态氮、铵态氮以及微生物量氮的影响。结果表明:减量施氮(300 kg/hm2)水平下,间作甘蔗鲜重产量较单作显著下降,但间作的土地当量比均大于1,且大豆产量为1.52和3.25 t/hm2。不同施氮水平对甘蔗鲜重无显著影响,施氮水平和种植模式对甘蔗单株氮吸收量、甘蔗收获后土壤硝态氮和微生物量氮均无显著影响。土壤氮素随甘蔗大豆的不同生长时期而变化,在甘蔗分蘖末期(大豆收获期)达到最低值,此时期减量施氮水平下甘蔗//大豆间作模式(1∶1)土壤硝态氮显著高于单作。综合以上结果,从提高土地利用率和保护农业生态环境考虑,甘蔗//大豆间作模式下减量施氮具有一定的可行性。

Sugarcane（Saccharum sinensis Roxb） is an important sugar crop in China which mainly produced in subtropical and tropical region of China.Wide row spacing（120 cm） and initial slow growth rate of sugarcane offers a suitable space and resources（water,nutrition,light） niche for intercropping in sugarcane.Meanwhile,over input of nitrogenous fertilizer was also a big problem which results in soil acidification and environmental pollution.How to reduce nitrogen application and design suitable sugarcane intercropping pattern is the key techniques to make the sugarcane production more sustainable in south China. In order to explore the sugarcane fresh yield and dynamic changes in nitrogen uptake by sugarcane,soil nitrate,ammonium and microbial biomass nitrogen,a field experiments were conducted in 2010 at experimental farm of South China Agricultural University（23°08′N,113°15′E）.The experiments were the randomized block design with two levels of N fertilizer（300 kg/hm2,500 kg/hm2） and four cropping patterns（sugarcane monoculture,soybean（Glycine max L.） monoculture,sugarcane//soybean（1 ∶ 1 rows） intercropping,sugarcane//soybean（1 ∶ 2 rows） intercropping）.All the treatments have three replicates,each plot（4.8×5.5 m） grows four rows of sugarcane except the soybean monoculture treatment in which grows 16 rows soybean. The results showed that sugarcane fresh yield significantly decreased in 1 ∶ 1 and 1 ∶ 2 rows intercropping systems compared to sugarcane monoculture under reduced N application（300 kg/hm2）,but the LER（land equivalent ratio） of the two intercropping treatments were bigger than 1,and harvested 1.52 and 3.25 t/hm2 soybean respectly.There is no significant difference between the sugarcane fresh yield of the two nitrogen application levels.Nitrogen rates and cropping patterns did not influence sugarcane′s nitrogen uptake,soil nitrate and microbial biomass nitrogen when the sugarcane harvested.Soil nitrogen in the plough layer changed with crops growth,the lowest content appeared at tillering（soybean harvest） growth stage of sugarcane,soil nitrate nitrogen content was remarkably higher in sugarcane//soybean intercropping（1 ∶ 1 rows） than sole cropping in this stage.In conclusion,intercropping patterns improved the LER,reduced nitrogen application did not notably affected sugarcane fresh yield,and the soil nitrogen content in plough layer was not different in all treatments.Sugarcane//soybean intercropping under reduced nitrogen application is feasible to practice in consideration of improving the utilization rate of land and agricultural environmental protection.