|Spargo, John - VA TECH, BLACKSBURG, VA|
|Alley, Marcus - VA TECH, BLACKSBURG, VA|
|Wallace, James - COLNIAL SWCD, QUINTON,VA|
Submitted to: Nutrient Cycling in Agroecosystems
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 9, 2008
Publication Date: July 19, 2008
Citation: Spargo, J.T., Alley, M.M., Follett, R.F., Wallace, J. 2008. Soil nitrogen conservation with continuous no-till management. Nutrient Cycling in Agroecosystems. 82:283-297. Interpretive Summary: Continuous no-till is an effective management practice in the Virginia middle coastal plain to conserve soil N. We found that the implementation of continuous no-till on farms previously using rotational or intermittent tillage resulted in the sequestration of 22.2 ± 21.2 kg N ha-1 yr-1 (0 – 15 cm). These data provide a quantitative estimate of the N sequestration rate within the top 15 cm for the region based upon on-farm observations. The conservation of soil N with continuous no-till management indicates improved N use efficiency of the cropping system. A substantial portion of the soil N conserved with continuous no-till management can become rapidly available and potentially lost from the system when intermittent tillage is used as a modifier to address perceived soil compaction, remove ruts, control weeds or incorporate residues. Therefore, the use of periodic or intermittent tillage of no-till cropping systems should only be practiced when absolutely necessary. When intermittent tillage is used, it should be synchronized with cropping to maximize the capture of mineralized soil N by growing vegetation. A portion of the additional N retained as SOM in no-till soils may potentially become available for crops. A soil based approach that quantifies organic N turnover may be necessary to improve the precision of fertilizer N recommendations in these systems.
Technical Abstract: Tillage management is an important regulator of organic matter decomposition and N mineralization in agroecosystems. Tillage has resulted in the loss of substantial amounts of organic N from the 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 sequestration rate with continuous no-till management of grain cropping systems and evaluate its impact on mineralizable and inorganic soil N. Samples were collected from 63 sites in 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 that ranged from 0 to 14 yrs. Forty-one of the sites had a history of biosolids application. Five soil cores were collected at each site 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 surprisingly 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. The implementation of continuous no-till management in this cropping system has resulted in conservation of soil N. [GRACEnet publication].