2008 Annual Report 1a.Objectives (from AD-416) (i) Estimate biomass production and nutrient reserve in leguminous cover crops, i.e. sunn hemp, and velvetbean, under an arid temperate vs. humid tropical climatic condition in vegetable production systems. (ii) Estimate mineralization rates of the above cover crops and carbon sequestration rates under the above agroclimatic vegetable production systems. (iii) Trace gas emissions and ammonia volatilization with different nutrient and residue management practices in a vegetable rotation system. (iv) Estimate nutrient transformation, trace gas emissions, and carbon sequestration during decomposition and residue turnover from biofuel coproducts and other agricultural wastes. 1b.Approach (from AD-416) Field studies will be conducted in Columbia Basin irrigated production region in WA (arid, temperate) and near Homestead, FL (humid, subtropical). Sunn hemp and velvetbean cover crops will be grown following the standard production practices for each of the above production regions. Total biomass production and nutrient reserves in each of the cover crops will be estimated. Following the incorporation of the cover crops, the decomposition of the residue, rate of mineralization, and carbon sequestration rate will be estimated. Trace gas emissions and ammonia volatilization will be evaluated under different fertilizers and residue management for potatoes, including fertigation, controlled resease fertilizer, and during decomposition and mineralization of organic amendments including biofuel coproducts and animal manures. 3.Progress Report Cover crops which grow and accumulate biomass at a rapid rate offer a great potential to sequestor carbon in soils. Biomass productions of Triticale, Ryegrass, Bellbean, Mustard, Purple Vetch, and White Clover were evaluated in a sandy soil (Quincy fine sand) from major potato production region in Washington, and a loamy soil (Krome gravelly soil) from Florida at either 25/20, 15/10, or 10/8 degree C - day/night temperatures. Biomass production of the above cover crops decreased at 10/8 degree C as compared to that at the higher temperature regimes. Biomass production was greater for Triticale, Ryegrass, and Bellbean than that for the rest of the cover crops. In field condition in south Florida, highest biomass production (2368 kg/ha) was obtained with Triticale and White Clover mixture which contributed upto 1000 kg/ha carbon. Progress on this project was monitored by the ADODR via phone and email correspondence.