| Popis: |
A seven-year no-tillage study was conducted at the North Carolina A&T State University Farm, Greensboro, North Carolina, from 1995 to 2001. The treatments were no-tillage controlled traffic (NC) and no-tillage full traffic (NF). No-tillage consists of opening a small slit in the soil by means of a coulter running ahead of a planter with openers. Wheel-traffic is controlled in NC by using alternate interrow areas such as traffic lanes. In the spring of each year, a 4.5-tonnes tractor was used to compact the soil surface in NF plots. The plots were planted on a corn-corn-soybean-soybean rotation. NF runoff and soil loss were not significantly different (p > 0.05) from NC in six of the seven years. The one year of difference occurred in 1997 when NF runoff and soil loss were significantly higher than NC. This was due to a series of high intensity rainstorms in July of 1997, which had return periods of 50 and 100 years. Without this event, there are no significant differences in NF and NC runoff and soil loss in all of the years. Total runoff and soil loss of NF is respectively, 1.2 and 2 times more than NC. This may indicate that NC represents a better management practice than NF. However, these differences are mostly caused by the single event (July 1997) of very low probability. Therefore, the long-term differences in runoff and soil loss between NF and NC may not be critical. Hence, for this case, farmers may use whichever system fits their management pattern; and runoff and soil erosion should not be significantly impacted. |
