Study the Effects of Organic Matter from Different Sources on Soil Physico-Chemical Properties and Crop Yield.

Abstract: Soil organic materials are composed of partially or completely decomposed plant and animal residues. The soils of arid and semiarid regions of Iran are found to be deficient in organic matter. Low levels of soil organic matter results in low fertility levels. The water holding capacity of soils will decrease with decreasing levels of organic matter resulting in severe compaction, exposing the soils to high rates of erosion. Therefore by adding organic materials to the arid and semiarid soils use could greatly improve the yields of crops. One way to improve the organic matter content of our soils would be to add animal manure, green manure, composted plant residues, wastes from agricultural materials as well as municipal wastes. A randomized complete block split plot experiment was carried out to determine the effect of the type and the rate of application of organic materials on the soil physical and chemical properties and the yields of agricultural crops. The main factor included the type of organic fertilizers and the subplots contained the rates of organic fertilizers added during the first year of the experiment. Organic fertilizers included wheat straw and stubble, animal manureand (cow and sheep), poultry manure, green manure, residues from dates, sesame residues, residues from salt tolerant bambooand, rice husks, composted sugarcane bagass, residues from licorice roots, crushed bambooand, composted tomato residues, as well as composted municipal wastes. The type and rate (2.5, 5.0 and 10 tons/ha) of these materials used varied from place to place. The crop grown in each location as well as the type of rotation were based on the prevalent situations of each location. Soil samples were collected for physicochemical analysis at the beginning and the end of every growing season, and the yields were determined as the plants response to the organic fertilizers. Statistical analysis of the data on yields obtained in different years showed significant main effects of fertilizer type on the yields. Furthermore the rates of addition of organic materials showed significant effects on the yields in some locations. The results showed as a whole that the soil ECand, saturation percentages, coefficient of water conductivityand for surface as well as lower horizons were significantly different and higher as compared to the control values, while acidity and apparent bulk densities were lower as compared with the control. Other soil parameters such as organic carbon, phosphorus content, available levels of nitrogen and potassium as well as the available water content of the soils had improved in most regions but remained unchanged in other areas.