Saturday, 15 July 2006

Duration of Continuous No-Tillage Management and Soil Nitrogen Status in the Virginia Coastal Plain.

John Spargo and Marcus Alley. Virginia Tech, Dept of Crop, Soil and Environmental Sciences, Blacksburg, VA 24061

Efficient N fertilization is paramount to both economic crop production and protection of ground and surface waters. 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. In 2004, approximately 54% of the annual crop production area of Virginia was managed no-till. Little research has been conducted to investigate the N status of long-term no-tillage soils in the mid-Atlantic Coastal Plain region. 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 agronomic crop production in the region. Half of the sites received biosolids 5 years prior to the sampling date. Five surface samples where collected from 0 - 2.5 cm, 2.5 - 7.5 cm and 7.5 to 15 cm immediately 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.

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