Physical environment near the surface of plowed and no-tilled soils

Abstract

Mechanical tillage is a dynamic soil process that influences the physical environment near the surface, thus affecting biological processes in the soil. Water content, bulk density, air permeability, hydraulic conductivity and organic carbon were compared for moldboard plowed and non-tilled conditions at five locations from east-central U.S.A. to the Great Plains. Soils were Blount, Maury, Nicollet, Webster and Crete-Butler cropped to continuous corn ( Zea mays L.), and Alliance and Duroc cropped to wheat/fallow ( Triticum aestivum L.). Major differences in soil physical characteristics between tillage practices were largely confined to the top 75 mm of soil. The volumetric water and organic carbon (C) contents of the 0–150-mm layer at time of sampling ranged from 8 to 66% and 12 to 75% higher, respectively, in no-tilled than in plowed soils. Bulk density was greater and total porosity in the surface layer was as much as 10% less for no-tilled than for plowed treatments. Because of generally higher water contents and/or lower porosity, the water-filled pore space (WFPS) in the 0–150-mm layer of no-tilled soils was 6–28% higher than that of plowed soils. Air permeability in the surface layer of no-tilled soil was less than for plowed, but there were no differences due to tillage in the 75–150-mm depth. Physical soil characteristics influence the soil water regime, and thereby affect rate of biological reactions in the soil. At many points in the soil drying cycle, water added to a no-tilled soil usually creates a less aerobic environment compared to adding the same amount of water to plowed counterpart.