Project ID



This study provided the first Iowa assessment of the availability of beef cattle manure phosphorus (P) for crops since the early 1970s.

Key Question

How should the current estimate of beef cattle manure phosphorus (P) crop availability in Iowa State University Extension and Outreach guidelines be updated?


This study showed that for most beef cattle manure types, and under most field conditions, the P availability is higher; ranging from 80 to 100 percent compared to fertilizer. Analysis of manure-soluble P and other fractions did not help to identify the reasons for variation in availability. To minimize risk of yield loss due to P deficiency, the lower part of the availability range should be assumed when the manure is applied to low-testing soils, and the higher part of the range assumed when the objective of the application is to maintain soil-test P in the optimum category for crops.

Principal Investigator(s)

Antonio Mallarino


Mazhar U. Haq, Nicholas E. Dagna

Year of Grant Completion