The effects of organic and inorganic materials on some physical properties of a sodic soil

The presence of excessive amounts of exchangeable sodium on sodic soils adversely affects the physico-chemical properties of these soils. Organic matter and minerals amendments were used to improve the properties of sodic soils. To study the effects of different levels (0, 2.5, and 5%) of alfalfa residue without or with gypsum and aluminum sulfate on physical properties of a sodic soil a greenhouse experiment with 9 treatments was conducted in Zanjan University using a completely randomized design and three replications. After addition of different treatments to soil samples, they were incubated for four months at moisture content of field capacity. Physical properties of the soil samples including stability of soil aggregates (measured as mean weight diameter), hydraulic conductivity and plant available water were measured after incubation of two and four months intervals. Aggregates with diameters of 250-500 μm and 500-1000 μm increased significantly with respect to control after 2 and 4 months of incubation respectively. The highest plant available water was obtained from treatments with 5% alfalfa residue+ gypsum or 5% alfalfa residue+ aluminum sulfate and these treatments increased this attribute by 26.5% and 23.5% respectively compared to control. The most effective treatment in increasing hydraulic conductivity was aluminum+ 5% alfalfa residue stood in second place. The results of this research indicate the importance of organic matter and calcium bearing compounds for improving physical properties of sodic soils.