Dissolved Nitrogen, Chloride, and Potassium Loss from Fields in Conventional and Conservation Tillage

Abstract

Losses of soluble nutrients from cropland and their transport to surface and groundwater are a continuing water quality concern. In this study, we evaluated tillage impacts on dissolved losses of ammonium (NH4-N), nitrate nitrogen (NO3-N), chloride (Cl), and potassium (K) during rotational cotton and peanut production. Tillage treatments were strip tillage (ST), in which crops were planted into 15 cm strips tilled into cover crop residue mulch, and conventional tillage (CT), in which all crop residues were turned into the soil prior to planting. Winter cover crops were used in both tillage systems. Tillage and irrigation treatments were uniformly applied within two 0.6 ha fields located on a moderately sloping hillslope in the southern Atlantic Coastal Plain region of south-central Georgia. Tile drains were installed at the base of the slope of each field to capture and measure lateral subsurface flow. Each field was subdivided into three 0.2 ha plots, with the three plots making up a single tillage block. H-flumes were used for flow measurement and sample collection. During the five-year study, annual precipitation ranged from 910 to 1488 mm, with an annual average of 1201 mm. Annual surface runoff averaged 17% of annual rainfall from the CT field and 11% from the ST field. Because of relatively low variability in concentrations, surface runoff loads closely tracked surface runoff volumes. Annual surface runoff loadings of NH4-N, NO3-N, and Cl from the ST treatment were foun…