Effects of continuous cultivation on ferrosols in subtropical southeast Queensland, 1. Site characterization, crop yields and soil chemical status
1995
Bell, M.J. | Harch, G.R. (Queensland Dept. of Primary Industries, Kingaroy (Australia)) | Bridge, B.J. (Commonwealth Scientific and Industrial Research Organisation, Toowoomba (Australia). Div. of Soils)
A range of crops grown in on-farm situations during 1986-90 were examined using paired sites to assess the extent of yield decline with time under cropping. All locations showed evidence of a significant reduction in crop growth (50-100 percent) where continuously cropped sites were compared with sites which had either never been cropped or which had been under grazed grass pasture for more than 20 years. In the absence of severe late season water deficits, this reduced growth rate was always reflected in lower (21-72 percent) crop yields at maturity. However, crop dry matter (DM) could interact with crop water use under conditions of late-season water deficiency to negate, or even reverse, early growth advantages on previously untilled soil. At least part of the observed yield reduction on continuously cropped soil was due to nutrient deficiencies resulting from depletion of both surface and subsurface reserves during cropping. Long-term cropping has resulted in depletion of soil K and Zn, organic C and total N status, and caused significant acidification. The reduction in soil organic C due to cropping was extreme, with continuously cropped areas having organic C levels of only 0.9 to 1.5 percent in the 0-10 cm layer-values which were only 25-40 percent of levels in untilled soil. Grazed grass leys were only partly successful in restoration of soil organic C status.
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