Case Studies of Present vs. Optimum P Use and Respective Development of Soil Test P at Selected Fields on Private Farms
In Finland about half of the cultivated fields have such high soil test P (STP) concentrations that P fertilization does not give yield increases and could be omitted for several years. In reality, P fertilization practices in farms are different, depending on whether manure or mineral P is used as P source. Generally, animal farms use more P inputs than those that rely on purchased P only. In this report we compared the present P fertilization practices to the optimum P use at farm level, and estimated the effect of adjusted P fertilization on soil test P levels in the future. We also calculated how P optimization could save P resources in the studied farms.
Most of the fertilized field parcels received more P than plants required for the 95 % of the maximum yields and this practice was more common for the parcels receiving manure P than for those fertilized with mineral P. Among the parcels fertilized with mineral P, P use was at a profitable level in two cases out of six. Three parcels did not receive any P applications due to excessive STP. Environmentally sound STP levels could be reached faster by adjusting the P fertilization according to plant requirement than with the current fertilization practices.
This report on P fertilization practices and soil test P at farm level was prepared as part of a work package 4 on manure standards in the project Baltic Manure.
Click here to read the report