Tuesday, November 14, 2006

Nitrogen Status in Continuous No-till Soils of the Virginia Coastal Plain.

John Spargo, B44N Smyth Hall, Virginia Tech, Virginia Tech University, Crop & Soil Environmental Sciences- 0404, Blacksburg, VA 24061 and Marcus Alley, Crop & Soil Env Sci Dept, VPI & SU, 416 Smyth Hall, Blacksburg, VA 24061-0403.

Elevated soil organic matter in long-term no-tillage soils may significantly influence N cycling and potentially result in reduced N fertilizer requirements for crops where N uptake patterns match N mineralization.  The objective of this research was to determine the relationship between duration of no-tillage management and soil N status.  Thirty-two sites where selected across three soil series in the Virginia Middle Coastal Plain with a history of no-tillage ranging from 2 to 14 years. All sites were in a corn (Zea mays L.) / wheat (Triticum aestivum L.) or barley (Hordeum vulgare L.) / double-crop soybean (Glysine max L.) rotation. The three soils series, Bojac loamy sand (Coarse-loamy, mixed, semiactive, thermic Typic Hapludults), Altavista sandy loam (Fine-loamy, mixed semiactive, thermic Aquic Hapludults), and Kempsville sandy loam (Fine-loamy, siliceous, subactive, thermic Typic Hapludults), represent a significant portion of the land area used for crop production in the region. Half of the sites received biosolids 5 years prior to the sampling date. Samples where collected from 0 - 2.5 cm, 2.5 - 7.5 cm and 7.5 to 15 cm following corn harvest in 2005 and analyzed for total C and N, 2 N KCl extractable [NH4+1 + NO3-1]–N and amino sugar N. Total C, N, and amino sugar N increased with increasing duration of no-tillage management, particularly in the 0 – 2.5 cm layer. Soils receiving biosolids had higher levels of total C and N, and amino sugar N, regardless of tillage or soil texture. Total C and N, and amino sugar N tended to be higher in the finer textured Altavista and Emporia soils regardless of tillage or biosolids history.  Future research will determine if increased N status of no-tillage soils results in decreased fertilizer N response and if changes in N fertilizer needs can be predicted using simple laboratory procedures.