农田沙漠化过程对土壤性质和作物产量的影响

地处北方半干旱农牧交错带东端的科尔沁沙地,是我国现代沙漠化最严重的地区之一。选择科尔沁沙地不同沙漠化阶段（非沙漠化、轻度、中度、重度和严重沙漠化）农田,研究了沙漠化发展过程对土壤有机碳、全氮、颗粒组成、土壤温度、土壤持水能力以及作物生物量的影响。结果表明,随着农田的风蚀,土壤发生粗化和有机质含量下降,土壤环境明显恶化,导致生物产量大幅度下降。从非沙漠化农田分别到轻度、中度、重度和严重沙漠化农田,100 cm深土壤有机碳含量下降34.4%、52.8%、81.6%和90.9%,全氮含量下降42.4%、58.5%、82.7%和92.6%。从非沙漠化农田到严重沙漠化农田,2～0.1 mm的土壤颗粒含量从64.4%增加到96.1%,0.1～0.05 mm的颗粒含量从28.8%减少到2.7%,小于0.05 mm的颗粒含量从5.9%减少到0.7%。严重沙漠化农田土壤温度比非沙漠化农田高3.0℃,土壤饱和持水量和田间持水量分别比非沙漠化农田低45%和53%,单株地上部生物量比非沙漠化农田低31%。非沙漠化、轻度、中度和重度沙漠化农田单位面积玉米产量分别比严重沙漠化农田高3.4、3.5、2.5和1.5倍。在科尔沁沙地,加强农田防护林建设,实施保护性耕作和增施有机肥是防止农田沙漠化和提高作物产量的根本措施。

Effects of desertification process on soil properties and crop yield of farmland

The Horqin Sandy Land,is located in the agro-pastoral transitional zone between the Inner Mongolian Plateau and the Northeast Plains of China（42°41＇ to 45°15＇ N,118°35＇ to 123°30＇ E）,and is one of the most seriously desertified regions of China.Five types of farmland along a desertification gradient（Non-,Light,Moderate,Severe,and Most severe desertification） in the Horqin Sandy Land were selected to investigate the effects of desertification on soil properties including carbon and nitrogen content,particle size distribution,temperature,and water holding capacity,and crop yield of farmland.The results showed that the coarse grain content in soil increased and organic matter decreased along the desertification development.The desertification process worsened the soil environment and resulted in the decrease of biomass conspicuously.From non-desertification to light,moderate,severe,and most-severe desertification farmland,soil organic carbon content decreased by 34.4%,52.8%,81.6%,and 90.9%,respectively,while total nitrogen content decreased by 42.4%,58.5%,82.7%,and 92.6%.From non-desertification to most-severe desertification farmland,soil particle content of 2～0.1 mm ranged from 64.4% to 96.1%,0.1～0.05 mm from 28.8% to 2.7%,and less than 0.05 from 5.9% to 0.7%.Compared with the non-desertification farmland,soil temperature in most-severe desertification farmland increased by 3.0 ℃,soil saturated water content and field moisture capacity decreased by 45% and 53%,and above-ground biomass decreased by 31%.The crop yield in non-desertification,light,moderate and severe desertification farmland was 3.4,3.5,2.5 and 1.5 times of that in most-severe desertification farmland,respectively.For preventing farmland from desertification and raising crop production in Horqin Sandy Land,it is essential to build farmland shelter belt,practice conservation tillage measures,and apply more organic fertilizer.