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

Abstract

【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 Buh desert 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.

Keywords

• soil amendment
• modified bentonite
• alfalfa
• growth and yield