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Title: Growth of tropical legume cover crops as influenced by nitrogen fertilization and Rhizobia

Author
item FAGERIA, N - Embrapa
item FERREIRA, E - Embrapa
item Baligar, Virupax
item KNUPP, A - Embrapa

Submitted to: Communications in Soil Science and Plant Analysis
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/17/2011
Publication Date: 2/19/2013
Citation: Fageria, N.K., Ferreira, E.P., Baligar, V.C., Knupp, A.M. 2013. Growth of tropical legume cover crops as influenced by nitrogen fertilization and Rhizobia. Communications in Soil Science and Plant Analysis. 44:3103-3119.

Interpretive Summary: In South America soils are eroded and infertile. Lack of adequate nitrogen is a major crop yield limiting factor in these soils. Legume cover crops provide vegetative cover to reduce soil erosion and add nitrogen to soils through their interactions with nitrogen fixing bacteria. Growth of the cover crops lablab, gray velvet bean, jack bean and black velvet bean in eroded soils improved considerably when nitrogen fertilizer or nitrogen fixing bacteria were added. The use of legume cover crops to improve the fertility of eroded and infertile soils appears to be an important management strategy. Farmers would benefit from the use of these cover crops due to reduced soil erosion, reduced production costs, and improved yields.

Technical Abstract: Tropical legume cover crops are important components in cropping systems due to their role in improving soil quality. Information is limited on the influence of nitrogen (N) fertilization on growth of tropical legume cover crops grown on Oxisols. A greenhouse experiment was conducted to evaluate the influence of N fertilization with or without rhizobial inoculation on growth and shoot efficiency index of 10 important tropical cover crops. Nitrogen treatment were: i) 0 mg N kg-1 (control or N0), ii) 0 mg N kg-1 + inoculation with Bradyrhizobial strains (N1), iii) 100 mg N kg-1 + inoculation with Bradyrhizobial strains (N2), and iv) 200 mg N kg-1 of soil (N3). The N X cover crops interactions were significant for shoot dry weight, root dry weight, maximal root length and specific root length, indicating that cover crop performance varied with varying N rates and inoculation treatments. Shoot dry weight is considered an important growth trait in cover crops and overall, maximal shoot dry weight was produced at 100 mg N kg-1 + inoculation treatment. Based on shoot dry weight efficiency index, cover crops were classified as efficient, moderately efficient and inefficient in N use efficiency. Overall, the efficient cover crops were lablab, gray velvet bean, jack bean and black velvet bean and inefficient cover crops were pueraria, calapo, Crotalaria, smooth crotalaria and showy crotalaria. Pigeonpea was classified as moderately efficient in producing shoot dry weight.