改性膨润土对沙地土壤改良及紫花苜蓿生物效应的影响

Amending Sandy Soils with Modified Bentonite to Improve Its Physical Properties and Crop Growth

【目的】探索改性膨润土掺量对沙地土壤结构、紫花苜蓿(Medicago sativa L)生物效应的影响,为提高沙地土壤持水性能及生产能力、紫花苜蓿产量及品质提供参考。【方法】采用室内盆栽试验,用高庙子膨润土改性后掺入沙土(采自乌兰布和沙漠)中制成试验用土,研究了改性膨润土掺量(0、3%、5%、7%、9%、11%)对土壤持水性能、土壤硬度、呼吸强度及紫花苜蓿生物效应的影响。【结果】不同掺量处理均能提高土壤持水性能、土壤硬度及呼吸强度,同时促进苗期紫花苜蓿的生长。与CK相比各掺量处理的平均日耗水量降低了18.3%、22.2%、28.1%、39.6%、40.2%,灌溉水量节约了21.7%、22.6%、28.3%、38.1%、38.3%。干物质量增加了146.4%、198.5%、-15.9%、-20.1%、-34.2%。紫花苜蓿叶片数增加了99.8%~492.9%,叶周长增加了3.6%~411.4%,叶、茎贡献率增加了1.8%~5.4%、5.9%~9.8%;比叶面积降低了55.7%~96.4%,根贡献率降低了10.1%~12.6%。【结论】改性膨润土可改善沙地土壤性状、提高持水性能,降低平均日耗水量,节约灌溉用水,同时提高了紫花苜蓿的产量,质量分数3.0%~5.0%的改性膨润土掺量为此试验沙地紫花苜蓿种植的适宜掺量。

【Objective】Sandy soil is less fertile and poor in water-holding capacity.The objective of this paper is to experimentally investigate the efficacy of amending it with modified bentonite to improve its physical properties and yield of alfalfa(Medicago sativa L.).【Method】The experiment was conducted in pots packed with sandy soil taken from the Ulan Buhdesert which was amended with the modified bentonite at ratios(weight/weight)ranging from 0 to11%.For each treatment,we measured the change in water-holding capacity,soil hardness,soil respiration,and the development and ultimate yield of the alfalfa.【Result】Adding modified bentonite to the soil increased its water holding capacity,hardness and respiration,as well as alfalfa growth,regardless of the amending ratios.Compared with CK without bentonite amendment,the amendment at ratio of 3%,5%,7%,9%and 11%reduced daily water consumption of the alfalfa by 18.3%,22.2%,28.1%,39.6%and 40.2%,respectively,saved irrigation water by 21.7%,22.6%,28.3%,38.1%and 38.3%respectively,and increased dry mass of the alfalfa by 146.4%,198.5%,-15.9%,-20.1%,-34.2%respectively.Benitoite amendment also increased the leaf numbers of the crop by between 99.8%and 492.9%,leaf circumference between 3.6%and 411.4%,depending on the amending ratio.We also found that bentonite amendment altered the composition of biomass of the alfalfa with the contribution from leaves and stems increasing from 1.8%to 5.4%,and 5.9%to 9.8%respectively,but reduced the specific leaf area ratio by 55.7%to 96.4%and fraction of root biomass by 10.1%to 12.6%,depending on the amending ratio.【Conclusion】Amending the sandy soil with modified bentonite can improve its physical properties,reduce daily water consumption of alfalfa while in the meantime increasing irrigation water use efficiency and the ultimate crop yield.For the alfalfa variety we studied,an amending ratio in the range of 3.0%~5.0%was optimal.