Submitted to: Soil Science Society of America Journal
Publication Type: Peer reviewed journal
Publication Acceptance Date: 7/1/2001
Publication Date: 7/1/2002
Citation: Shaver, T.M., Peterson, G.A., Ahuja, L.R., Westfall, D.G., Sherrod, L.A., Dunn, G.H. 2002. Surfaces soil physical properties after twelve years of dryland no-till management. Soil Science Society of America Journal. (2002) 66:1296-1303. Interpretive Summary: The traditional dryland cropping system in this region was conventional tillage management of crop-fallow, commonly wheat-fallow, which produced 1 crop every two years. In order for the fallow period to be successful, weeds and volunteer plants need to be controlled by tillage to provide soil profile water storage. Summer fallowing every other year can be economically and environmentally costly. After conversion to a no-tillage system 12 years ago, physical properties of the surface 2.5 cm of soil were improved by more intensive cropping systems when compared with WF. Cropping systems which increase residue levels returning to the soil greater than WF improved surface soil physical properties by reducing bulk density and increasing total and effective porosity and macroaggregates.
Technical Abstract: Water is the principle limiting factor in dryland cropping systems. Surface soil physical properties influence infiltration and cropping systems under no-till management may affect these properties through residue addition. The objectives of this study were: (i) to determine how cropping intensity and topographic position affect soil bulk density, porosity, sorptivity, and aggregate stability in the surface 2.5 cm of soils at three eastern Colorado sites; and (ii) to relate these properties to crop residue returned to the soil surface. No-till cropping systems had been in place on three slope positions, at three sites, for 12 yr prior to this study. Wheat (Triticum aestivum L.) Corn (Zea mays L.) - fallow (WCF) and continuous cropping cropping (CC) systems were compared with wheat-fallow (WF) on summit and toeslope positions at two sites (Sterling and Stratton), and at the third site (Walsh) wheat-sorghum [Sorghum bicolor (L.) Moench] - fallow (WSF) replaced WCF. Cropping systems (CC and WCF of WSF) that returned more crop residue decreased bulkdentisy and increased total and effective porosities compared with WF. Site and slope positions that produced more crop residue also improved these properties. However, sorptivity developed no significant differences as a result of cropping system. Macroaggregates made up a higher percentage of total aggregates in CC and WCF or WSF compared with WF in proportion to residue added and were also a function of clay content of the soil at different sites and slope positions. These factors enhance the potential for greater infiltration and hence greater water availability for crops.