Water erosion, Crop development stages, Conservation tillage, Soil loss tolerance - T value
Abstract
Water erosion was recorded during a four-year period (1994-1998.) on Luvic stagnosol (pseudogley), in the Daruvar area (Central Croatia), in different crop development stages according to USLE, under six tillage treatments in growing common arable crops in the common crop sequence. A much higher rate of erosion, higher than Soil loss tolerance (T value) was recorded in the growing of spring crops (row crops) than in winter crops of high plant density, where it was below the T value. In the growing of spring crops, the critical period with maximal water erosion was the period of seedbed preparation (SB period according of USLE), the period just after sowing. In the growing of maize and soybean, this is the period when over 80% of the overall annual erosion occurs in all tillage variants. As expected, the maximal rate of soil erosion, higher than the T value, was recorded in the standard plot according to USLE, followed by the variant of conventional up/down the slope tillage. Soil erosion was much smaller and below the T value in the no-tillage variant and in all variants with tillage across the slope. This means that these variants of soil tillage can be defined as conservation tillage in agroecological conditions of this part of Croatia. In growing winter crops of high density (wheat and oil seed rape), no critical periods were observed and erosion was much below the T value and was uniformly distributed throughout the whole growing season. According to the results, to reduce soil erosion below the T value on slopes of inclination higher than 9%, soil conservation practices are all tillage operations across the slope and/or a reduced crop rotation, without row crops.
