Influence of Tillage On Nitrate Leaching Losses in the Virginia Coastal Plain.

Due to conservation awareness, improved technology, and increased fuel costs, no-till management has been implemented on a significant portion of U.S. cropland. Continuous no-till management can have a significant influence on soil N cycling and fertilizer N use efficiency. It has also been suggested that NO₃-N leaching losses may be increased with no-till cultivation since infiltration rates are generally increased. Little research has been conducted to investigate NO₃-N leaching from soils managed using continuous no-till in the Mid-Atlantic Coastal Plain and studies conducted in other regions have produced conflicting results. In order to compare NO₃-N leaching losses between tillage systems, four long-term no-till sites paired with four rotational tillage sites across four soil series were selected. The soils selected for study represent the majority of land area used for agronomic crop production in the region. Cropping sequence at all locations was a corn (Zea mays) – wheat (Triticum aestivum) or barley (Hordeum vulgare) – double crop soybean (Glycine max) rotation. Three passive capillary wick samplers were installed 100 cm below the soil surface at each site. Leachate samples were collected from September 2005 through September 2009, analyzed for NO₃-N and reported on a concentration and mass basis.  There were no consistent effects of tillage management on the concentration or mass loss of NO₃-N leached. There was a rotational effect, with most of the NO₃-N losses occurring during periods of low evapotranspiration (i.e., fallow period following soybean harvest). This illustrates the value of cover crops during fallow periods to minimize NO₃-N leaching losses.