秸秆还田与全膜双垄集雨沟播耦合对半干旱黄土高原玉米产量和土壤有机碳库的影响

Effects of coupling film-mulched furrow-ridge cropping with maize straw soil incorporation on maize yields and soil organic carbon pool at a semiarid loess site of China

全膜双垄集雨沟播是我国旱作农业上的一项创新技术。该技术因集覆膜垄面集雨沟播、覆盖抑蒸和增加土壤温度为一体,在半干旱黄土高原地区玉米种植中增产效果突出而被大面积推广。但是目前该技术连续使用下土壤肥力的可持续性及其调控途径不清楚。通过将田间实验与土壤有机碳的物理分组技术相结合,研究全膜双垄集雨沟播对土壤有机碳库的影响,来评估将秸秆还田纳入全膜双垄集雨沟播玉米种植体系的可行性。实验地点位于甘肃省榆中县小康营乡(35°54'N,104°05'E;海拔2013 m;多年平均降雨量388 mm)。实验在垄沟种植方式的基础上设置秸秆不还田不覆膜(对照,CK)、秸秆还田(S)、地膜覆盖(M)和秸秆还田+地膜覆盖(S+M)4个处理,重复3次。实验于2009年3月开始2010年10月结束。除了对玉米籽粒产量进行测定之外,分别于每年的播种和收获时对表层15 cm土壤总有机碳、颗粒有机碳(粒径2—0.05 mm)和轻组有机碳(密度<1.8 g/cm3)含量进行了测定。同时在玉米不同生育时期对表层15 cm土壤微生物量碳、"-葡萄糖苷酶活性、碱性磷酸酶活性和脲酶活性动态进行了测定。研究结果表明,与CK处理相比M和S+M处理分别增加玉米产量89%-105%和93%-136%,但是S处理对玉米产量没有影响。综合2a的测定结果,与CK相比较S、M和S+M处理对土壤总有机碳含量没有影响,但是M处理具有降低土壤颗粒有机碳和轻组有机碳含量的趋势,而S或者S+M处理具有明显的增加土壤颗粒有机碳和轻组有机碳含量的趋势。与M处理相比较,S+M处理增加土壤颗粒有机碳和轻组有机碳含量的效果比与CK处理相比较的效果更明显。与CK相比较,S、M和S+M处理都能够不同程度地增加土壤微生物量碳和"-葡萄糖苷酶、碱性磷酸酶和脲酶的活性,尤其以S+M处理的增加效果更明显。相关分析结果显示,不同处理土壤中3种酶活性与微生物量碳含量均呈极显著正相关关系。研究结果说明全膜双垄集雨沟播可以显著增加玉米产量,但是连续使用可能对土壤有机碳库有不利影响;而纳入秸秆还田对于全膜双垄集雨沟播技术引用下土壤有机碳库和微生物活性的维持或者提高具有积极作用。

Plastic film mulched furrow-ridge cropping is a recent modification of maize cropping pattern. By excluding evaporation, redistributing precipitation from ridges to furrows and increasing soil temperature, plastic film mulched furrow- ridge pattern can significantly enhance maize grain yields and thus it has been widely extended on semiarid Loess Plateau formaize production. However, the sustainability of soil fertility, and related soil managemental practices have been limitedly studied under continuous application of this cropping pattern. This research was therefore designed to investigate effects of plastic film mulched furrow-ridge maize cropping on soil organic carbon pools and the possibility of introducing the soil incorporation of maize straws into this cropping pattern. The research site （35°54＇N, 104°05＇ E） was located at Xiaokangying, Yuzhong County of Gansu Province, with an altitude of 2013 m and annual precipitation of 388 mm. The experimental design included four treatments, namely, nil-straw incorporation plus nil-mulch （ control）, straw incorporation（S）, film mulch （M） , and straw incorporation plus film mulch （S＋M）, with 3 replicates on a furrow-ridge micro-relief- prepared field. The experiment started in March 2009 and ended in October 2010. In addition to the measurement of maize grain yields, soil samples were taken from the top 15 cm layer at sowing and harvesting in each experimental year for determininaions of total soil organic carbon, particulate organic carbon （particle size 2- 0. 005 mm） and light organic carbon （density 〈 1.8 g./cm^3） concentrations. Soil microbial biomass carbon and activities of β-glucosidase, alkaline phosphatase and urease were also periodically analyzed for the top 15 cm layer under different treatments through maize growth season each year. Compared to control, M and S＋M treatments improved maize grain yields by 89%- 105% and 93%-- 136%, whereas S treatment did not affected maize grain yields. Over two years, total soil organic carbonconcentration was not changed by S, M or S＋M, compared with control. However, M inclined towards decreasing but S or S ＋M treatment showed increasing, particulate organic carbon and light organic carbon concentrations in soils. The increasing effect in particulate or light organic carbon pool with S ＋ M treatment was more significant when compared to M than compared to control. Soil microbial biomass carbon and activities of 13-glucosidase, alkaline phosphatase and urease were increased by S, M or S＋M, compared to control. The increasing effect in soil microbial biomass carbon or activities of three enzymes with S ＋ M treatment was more significant when compared to S or M. Further, soil 13-glucosidase, alkaline phosphatase and urease activities all positively correlated to soil microbial biomass carbon concentration over treatments and periodical measurements for two experiment years, respectively. Our preliminary results showed although plastic film mulched furrow-ridge cropping markedly increased maize grain yields but may have a potential to decrease soil organic carbon pool; it was feasible to introduce maize straw into this cropping system for a favorable soil organic carbon balance and microbial activity.