EFFECTS OF FERTILIZER, BARNYARD MANURE, AND CROP RESIDUES ON IRRIGATED CROP YIELDS AND SOIL CHEMICAL PROPERTIES

Abstract

Barnyard manure, N fertilizer, corn stovers, and sugar beet tops were incorporated into the soil singly and in combination in an irrigated four-course rotation (sweet corn, soft spring wheat, sugar beets, and sugar beets) that completed four cycles. The application of manure at 27 t/ha every 4 yr increased the organic matter (OM), N, P, and K of the soil and increased yields of 1st-yr sugar beets by 31% in the last cycle. When 66 kg N/ha was combined with the manure, yields of 1st-yr sugar beets increased by 53%. The responses by the 2nd-yr sugar beets were smaller. Manure, and manure plus N fertilizer, increased yields of sweet corn by 11 and 28%, but wheat yields were unaffected. The benefits of manure and N fertilizer became apparent during the second cycle and increased with advancing years. The effects of the crop residue treatments were less pronounced than those of the fertility treatments and took longer to become manifest. Incorporating sugar beet tops or corn stovers into the soil increased beet and corn yields but not wheat yields. Sugar beet yields responded more to the residue treatments when grown without manure or N fertilizer than when the fertility treatments were included. Soil Ca and Mg were not affected by fertility or residue treatments. The soil amendments affected the chemical characteristics of the OM.