SPRING WHEAT-STRAW PRODUCTION AND COMPOSITION AS INFLUENCED BY TOPSOIL REMOVAL

Wind and water erosion have resulted in reduced crop productivity and created soil management problems. Management of crop residues can be e ffective for soil erosion control, but influences of soil erosion on c rop residue production is unknown. The purpose of this study was to de termine total residue production and residue N and P concentration and content for 8 yr as influenced by topsoil removal and additions of N and P fertilizer for a spring wheat (Triticum aestivum L.)-fallow syst em. Total straw production for the first increment of P increased appr oximate to 14% for 0.00- and 0.06-m soil removal treatments compared w ith approximate to 33% for 0.12- and 0.18-m soil removal treatments. T otal straw production was increased more than total grain production w ith the addition of N and P fertilizer. Total straw production for 0.1 2- and 0.18-m soil removal treatments needed at least 20 kg P ha(-1) a nd 35 kg N ha(-1) to equal or exceed that for 0.00-m soil removal trea tment with no fertilizer additions. Total straw N content decreased 33 % as soil removal increased from 0.00 to 0.18 m. While total straw P c ontent was considerably less than total straw N content, both decrease d about 32% for 0.18 m compared with 0.00-m soil removal treatments. G reater total straw N and P content for the 0.00-m soil removal treatme nt was due to greater total straw production as well as greater N and P concentrations. Consequently, cycling of N and P may be reduced for eroded soils due to low quantities of residue as well as low N and P c oncentrations in the residues.