Effect of Type and Amount of Organic Solid Waste Composts on Physical Properties of Two Different Soils

Unsuitable agronomic management, such as intensive cropping and removal of whole crop residue from soils, has caused a gradual and continuous decline of soil organic matter in many arid and semi-arid regions. This mismanagement has resulted in improper soil physical properties. Application of organic wastes composts containing municipal solid waste and sewage sludge composts could solve the problem. Addition of composts to soil leads to the development and stability of soil structure. In order to study the effect of organic compounds on soil physical properties, this study was carried out with a completely randomized design in a factorial experiment in three replications. The treatments included soil type (silty loam and clay), type of compost (municipal solid waste, sewage sludge, and cow manure), and the amount of organic fertilizers (0, 75, 150, and 300 m3 / ha equivalent to 0, 175, 350, and 700 cm3/pot). Soil samples were air-dried, passed through 2 mm sieve, and mixed with composts treatments and filled in 7-liter pots. Physical properties of soil samples including bulk density, particle density, porosity, dispersible clay content and wet and dry mean weight diameter of aggregates (MWD) were measured. The highest decrease in soil bulk density and dispersible clays and an increase in wet MWD were observed in the highest rate of sewage sludge application. Effects of organic amendments on soil particle density, porosity, and dry MWD were not significant. Decrease in bulk density and dispersible clay content was more in the silty loam soil, while the increase in dry and wet MWD was higher in the clay soil.