ABSTRACT
Application of animal manures to cultivated soils has been increasing steadily in the last decades because of the need for lower disposal costs and for the recycling of nutrient elements in the soil crop system. Few studies are available on the effects of long-term application of animal manures on soil physical properties that may influence soil productivity and prevent soil degradation. The addition of manures to soil has been found to be an effective management practice not only to increase the aggregation but also to increase the aggregate stability. The magnitude of the improvement of aggregate stability and of the other physical properties depends not only on the amount of organic matter but also on the type and quality of organic materials present in the manures added to the soil. Generally, the addition of organic manures to soil significantly reduced penetration resistance when compared with control and chemical-fertilizer amended soils.
