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United States Department of Agriculture

Agricultural Research Service



2011 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. (v) Investigate real-time changes in soil water contents and temperature that influence the cover crops residue decomposition, N mineralization and transport, and carbon sequestration. (vi) Estimation of soil water mass balance to predict leaching of water and nutrients below the rootzone. (vii) Collection of field data for validation of potato growth simulation model in commercial growing conditions to incorporate nutrient and water dynamics component to enhance nutrient and water uptake efficiencies.

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 release fertilizer, and during decomposition and mineralization of organic amendments including biofuel coproducts and animal manures. Formerly 5354-21660-001-06S (10/08). Soil water, temperature and conductivity sensors will be installed in irrigated potato field for real-time measurement and estimation of soil water mass balance. Biomass samples will be taken for evaluation of crop growth, nutrient distribution and validation of growth simulation model predictions.

3. Progress Report
A field experiment was conducted 6 cover crop species (sunnhemp, velvetbean, sorghum, sudangras, okra, cowpea, and caster bean) in mono- and bi -culture along with a fallow treatment. These cover crops were mowed and incorporated into the soil in November, 2010, and snap bean cultivar - Inspiration was grown from December, 2010 to March, 2011. The major results are: 1) Sunn hemp produced the largest amount of biomass (over 12 Mg/ha); 2)Bi-culture of legume with non-legume significantly improved the total amount of biomass compared to the monoculture of the same species; 3)The total amount of N accumulated by sunnhemp was about 280 kg/ha in contrast to less than 50 kg/ha N by sorghum sudangrass, and 20 kg/ha by okra; 4)Soil fertility based on subsequent crop growth status was improved significantly by growing and incorporation of all cover crops, especially the legume cover crops; and 5) The yield of snap bean ranged from 6.9 to 11.0 Mg/ha when following the monoculture of cover crops, and from 6.7 to 12.8 Mg/ha when following the bi-culture of cover crops, and 2.5 Mg/ha when grown after fallow. This project contributes to objective 1b of the parent project plan. Monitoring of the project was accomplished by phone and email contact with the cooperators.

4. Accomplishments

Last Modified: 2/23/2016
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