Soil Nitrogen Conservation with Continuous No-Till Management of Grain Cropping Systems in the Virginia Coastal Plain.

Tillage management is an important regulator of organic matter decomposition and N mineralization in agroecosystems. Tillage has resulted in the loss of considerable organic N from surface soils. There is potential to rebuild and conserve substantial amounts of soil N where no-till management is implemented in crop production systems. The objectives of our research were to measure N conservation rate with continuous no-till management and evaluate its impact on mineralizable and inorganic soil N. Samples were collected from 63 production fields using a rotation of corn (Zea mays L.) – wheat (Triticum aestivum L.) or barley (Hordeum vulgare L.) – double-crop soybean (Glysine max L.) across three soil series [Bojac (Coarse-loamy, mixed, semiactive, thermic Typic Hapludults), Altavista (Fine-loamy, mixed semiactive, thermic Aquic Hapludults), and Kempsville (Fine-loamy, siliceous, subactive, thermic Typic Hapludults)] with a history of continuous no-till ranging from 0 to 14 yrs. Thirty-one of the sites had a history of biosolids application. Soil cores were collected from 0 – 2.5, 2.5 – 7.5 and 7.5 – 15 cm and analyzed for total N, Illinois soil N test-N (ISNT-N), and [NH₄+NO₃]-N. A history of biosolids application increased the concentration of total soil N by 154 ± 66.8 mg N kg^-1 (310 ± 140 kg N ha^-1) but did not increase ISNT-N in the surface 0 – 15 cm. Continuous no-till increased the concentration of total soil N by 9.98 mg N kg^-1 yr^-1 (22.2 ± 21.2 kg N ha^-1 yr^-1) and ISNT-N by 1.68 mg N kg^-1 yr^-1 in the surface 0 – 15 cm.