Effect of fresh and composted cattle manure on phosphate retention in soil

In an adsorption study P was added as fresh or composted cattle manure or as inorganic P to soil suspensions with different P status. P added with fresh and composted manure was adsorbed to a lesser degree on the soil than the added inorganic P. Fresh manure reduced P adsorption more than did composted manure, Both types of manure contained simple organic acids, which have earlier been shown to influence P sorption. The amount of organic acids was greater in the fresh manure than in the composted manure. The efficiency of the manure in reducing P retention increased with increasing manure additions and with increasing P status of the soil. In soils with a very high level of plant-available P (P-AL), manure additions resulted in a net desorption of P.