Corn Fertility Treatments and the Surface Structure of a Poorly Drained Soil

Abstract

AbstractFertility treatment effects on annual measurements of bulk density, total porosity, and air‐filled porosity taken from the 0.05‐ to 0.15‐m depth of a Brookston clay loam soil (clayey, mixed, mexic Typic Haplaquolls), inclusive from 1957 to 1982, were evaluated. Additional bulk density, porosity, stability, and penetration resistance measurements were made on samples taken from the 0.05‐ to 0.15‐m and 0.15‐ to 0.25‐m depths in 1983. The treatments were (i) continuous corn (Zea mays L.) with no fertilizer; (ii) continuous corn with 298 kg/ha NH4NO3 annually; (iii) continuous corn as in (ii) plus 672 kg/ha of 5–8.8–16.6 (5–20–20) annually; and (iv) a corn, oats (Avena sativa L.), and alfalfa (Medicago sativa L.) rotation receiving 168 kg/ha of 5–8.8–16.6 (5–20–20) for oats. In general, bulk density increased as total and air‐filled porosities decreased with time for all treatments. However, the rotation treatment had lower bulk densities and higher total porosities than the continuous corn treatments. There were no significant differences in bulk density or porosity among the continuous corn treatments. The 1983 stability and penetration data did not show any meaningful treatment effects. However, the stability data illustrate the weak structure of this soil. Monoculture corn appears to play a minor role in the structural deterioration of this poorly drained, weakly structured soil.