Assessing the agronomic benefit of noninversion tillage for improving soil structure following winter grazing of cattle and sheep

摘要

Severe treading damage to soils often occurs when cattle and sheep graze standing forage crops during winter. Soil recovery is a long process that may take several months if not years. Noninversion tillage can speed up the recovery process by improving drainage and air diffusion. This research assessed the ongoing benefit of noninversion tillage for improving soil structure relative to non-tillage. This assessment was made following a land-use transition from winter forage cropping to re-establishment of seasonal pasture that was rotationally grazed by cattle or sheep. Prior to commencement of this study, the research site had poor soil structure due to four consecutive years of cattle and sheep grazing of winter forage crops [macroporosity (0-100mm) 0.075 and 0.113m(3)/m(3) under cattle and sheep, respectively]. Tillage was effective in increasing soil macroporosity to ca. 0.175m(3)/m(3) under both grazing classes, which was significantly higher than nontilled soils (ca. 0.140m(3)/m(3), 0-100mm depth). Improvements gained from tillage generally did not persist longer than 18months. Average annual pasture production in tilled plots was 22.1 and 20.9tons of dry matter per hectare (tDM/ha) for respective cattle- and sheep-grazed plots, while in the nontilled plots, it was 19.1 and 18.6tDM/ha, respectively. Results indicate noninversion tillage can provide an immediate increase in the porosity of compacted soils and improve pasture growth. However, processes involved in the formation of resilient soil aggregates are curtailed if subsequent grazing events coincide with high moisture content that causes recompaction.