Abstract
Under the environmental conditions of the central sector of Saudi Arabia, El-Gassim region, two field experiments were conducted on a sandy soil in the winter seasons of 1990-91 and 1998-92. Town refuse compost, at rates of 0.0, 16.5, 33.0, 49.5 and 66.0 t ha-1, was incorporated into the soil to a depth of 10 cm. The effect of the compost in optimizing the physical conditions of the sandy soil, as well as growth, nutrient uptake, grain and straw yields and water use efficiency of wheat were studied. The results indicated that the various application rates through the two seasons of growth were significantly correlated with improvements in the physical properties. The manure stimulated suitable conditions for plant growth and development, and acted as a good substratum for microbial activity. This was positively reflected in the magnitudes of dry weight, biological crop yield, root weight, nutrient uptake, straw and grain yields, grain protein yield and water use efficiency. Generally, 33.0 t ha-1 of the manure was considered to be the optimum application rate under the conditions of the present investigation. Moreover, the soil physical properties were significantly correlated with the results obtained for straw, grain and protein yields of wheat during both seasons. Multiple regression analysis revealed that the degree of aggregation is the important soil property for wheat production in sandy soils.