|PAPPAS, E - Retired ARS Employee|
Submitted to: Soil and Tillage Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/10/2015
Publication Date: 6/23/2015
Publication URL: http://handle.nal.usda.gov/10113/61155
Citation: Smith, D.R., Pappas, E.A. 2015. Vertical tillage impacts on water quality derived from rainfall simulations. Soil and Tillage Research. 153:155-160.
Interpretive Summary: Agriculture has been identified as the number one contributor to sediment and nutrient (nitrogen and phosphorus) loss to rivers, streams, reservoirs and estuaries. Farming without tilling the soil has helped reduce the amount of sediment entering the surface water network, however some are blaming no-till farming on increasing the amount of soluble nutrients (the form most readily available to aquatic life such as algae) leaving farm fields. A light tillage technique, known as vertical tillage, that only works in the upper 1-2 inches of soil has been promoted by some conservationists as one method to take advantage of no-till’s sediment reduction benefits and the incorporation of fertilizer nutrients that occurs with tillage. This study was conducted to test the influence of vertical tillage on sediment and nutrient losses from fields. Runoff was delayed on vertical till plots compared to no-till plots, however, the rate of runoff from the vertical tillage treatment once it started was much greater. Vertical tillage resulted in greater sediment loads (>3 fold increase) and total phosphorus (>2 fold increase) when compared to no-till. Our results showed that vertical tillage may have negative impacts on sediment and nutrient loadings to surface runoff. Additional research is needed to better understand the overall impacts of vertical tillage before a broad recommendation to adopt this practice should be made.
Technical Abstract: Increasing soluble phosphorus (P) loads to Lake Erie occurring around the same time that the implementation of no-tillage in the watershed has led to speculation that this important conservation practice is a primary cause of the soluble P loading. Thus, conservationists are interesting in finding farming practices that will minimize stratification of P, which may be common in no-tillage, while also minimizing erosion losses that result from conventional tillage practices. This study was conducted to determine if a shallow vertical tillage practice was sufficient to minimize P loading from long-term no-tillage fields, while optimizing for erosion. Rainfall simulations were performed on no-tillage and vertical tillage plots (5 X 1 m) sufficient to produce 30 min of runoff. Runoff was collected every 2.5 min, and analyzed for sediment and nutrients (NH4-N, NO3-N, TKN, soluble P and total P). Runoff was delayed by 17 minutes using vertical tillage; however, the steady-state rate of runoff was significantly greater from vertical tillage compared to no-tillage. There were no differences for N from runoff (NH4-N, NO3-N, or TKN). There was a trend of slightly higher soluble P loads from vertical tillage than no-tillage. Total P losses were correlated with sediment, and were observed to be higher from vertical tillage than no-tillage. The primary advantage that vertical tillage has with respect to nutrient losses is in delaying runoff initiation, however this effect could be nullified in subsequent runoff events. If P loadings to surface waters is the primary concern, such as is the case in the Great Lakes basin, it would appear from the data presented in this study that vertical tillage is not the solution to the problem, and in fact may impose greater risks due to greater erosion and associated total P losses.