Submitted to: Soil & Tillage Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 13, 1997
Publication Date: N/A
Interpretive Summary: Stubble mulch tillage and no-tillage are suited for dryland crops in the Great Plains, but there is concern if using no-tillage for a long time will harm the soil and reduce crop yields. We measured soil bulk density, penetration resistance, and water content in 1994 in plots of a study started in 1982 on Pullman soil at Bushland, Texas, where stubble mulch and dno-tillage were used for growing dryland winter wheat and grain sorghum. Soil density and penetration resistance always increased and water content often increased with depth. Soil density and pentration resistance were lower in the tillage layer in stubble mulch plots that were loosened by tillage than in no-tillage plots that were not loosened. No definite trends for soil density were found below 10 cm (4 inches). Soil penetration resistance often was greater with no-tillage than with stubble mulch tillage below 10 cm, even though water content was greater with no- tillage. Penetration resistance was related to bulk density and water content of the entire soil profile and for most depth increments with stubble mulch tillage. With no-tillage, density and water content of the profile were related to penetration resistance, but it was related only to water content for the different soil depths. We believe this is due to the stable soil pores that develop in no-tillage soils due to root channels and soil organisms. Even though penetration resistance was greater with no- tillage, crop yields have been as good or better with no-tillage than with stubble mulch tillage. Based on our measurements and crop yields for the study, we believe long-term use of no-tillage will not reduce crop yields or harm this and similar soils under dryland cropping conditions.
Technical Abstract: Stubble mulch tillage (SMT) and no-tillage (NT) are suitable for dryland crops in the Great Plains, but there is concern if long-term use of NT will affect crop yields, soil quality, and production sustainability. We determined effects of using SMT and NT in several dryland winter wheat and grain sorghum cropping systems on soil bulk density (BD), penetration resistance (PR), and water content (WC) in 1994 in plots of a study starte in 1982 on Pullman (Torrertic Paleustoll) soil at Bushland, TX. Data were analyzed to compare tillage method, cropping system, rotation phase, land condition (level or nonlevel), and crop effects on BD, PR, and WC. Soil BD and PR always increased with depth and WC often increased. The tillage X depth interaction effect also was significant. Soil BD and PR were lower in the tillage layer in SMT than in NT plots, but no definite trends occurred for BD below 10 cm. The PR often was greater with NT than with SMT below 10 cm, even though WC was greater with NT. Soil BD, PR, and WC differed also for some comparisons other than those involving tillage. Regression analyses showed PR was related to profile BD and WC and most depth increments with SMT, but to profile BD and WC and only to WC for depth increments with NT. This indicates a strength factor largely independent of BD and affected by WC influences PR of NT soil. We concluded that stable biopores reduced effects of BD differences among NT plots and that NT soils developed a rigid structure independent of BD. Although PR was greater with NT, it has not resulted in lower crop yields in plots used for the study. Results of this study and associated crop yields, therefore, suggest long-term use of NT will not impair the quality and production sustainability of this and similar soils under dryland cropping conditions.