1. Selected Soil Chemical Properties and Corn Grain Yield Under Different Manure Systems

The Iowa Department of Agriculture and Land Stewardship estimated 1987 farm animal populations to be 4.6 million cattle and calves and 13.8 million hogs and pigs (26% of the nation's hogs). The animals produced about 141,987 tons of plant available N if 50% of the excreted N is available the first year of application. This amounts to 22 lb of N for every corn acre in Iowa. Most of the livestock operations are intensive with high populations of animals on a sniall land area. Nutrients in feed are...