THE ROLE OF MANURE IN THE MANAGEMENT OF PHOSPHORUS RESOURCES AT AN ITALIAN CROP-LIVESTOCK PRODUCTION FARM

A quantitative knowledge of P cycling in dairy farms during a producti on cycle is the basis for optimizing fertilizer P management, because utilization of P by farm animals and its transfer to barn products are incomplete; animal manure represents a valuable source of P to sustai n crop requirements. The nutrient content of manure is always difficul t to determine precisely, because of the variability and fluctuation i n daily water content and composition. Estimates of the P content of e ach material that moves to, from and within a dairy farm located in Lo mbardy were determined for one year by collecting farm data, sampling and analyzing farm materials (feeds, beddings, milk, hays and silage, etc.) and estimating through model calculation P retained in animals a nd in farm wastes. Two subcycles were investigated: the barn subcycle and the soil-crop subcycle, connected together by wastes, grasses and corn silage. The overall P balance in the farm studied with total stoc king of 1.1 t of liveweight/ha, indicated a high manure potential for crop-needs that excludes use of inorganic P fertilizers. Moreover, det ailed analysis of the various P pools has shown the relative contribut ion of each component to P cycling at the farm. (C) 1997 Elsevier Scie nce B.V.