Submitted to: Australian Journal of Agricultural Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/20/2007
Publication Date: 1/1/2008
Citation: Vieira, F.C., He, Z.L., Wislon, P.C., Bayer, C., Stoffella, P.J., Baligar, V.C. 2008. Response of representative cover crops to aluminum toxicity, phosphorus deprivation, and organic amendment. Australian Journal of Agricultural Research. 59:52-6. Interpretive Summary: Aluminum (Al) toxicity in plants is a major problem in acidic soils. The presence of organic substances often alleviates Al totoxicity. Added organic matter forms bind with Al, thereby reducing its activity in acidic soils. Cover crops are capable of adding high amounts of organic matter, and is a promising strategy for alleviating Al toxicity without using a large amount of costly lime in this experiment. Aqueous extracts of residues from three cover crop (cowpea, black oats and lablab) residues grown with or without aluminum, phosphorous and organic matter were used to see their effect on growth and performance of the cover crops. Organic extracts alleviated aluminum toxicity, improving plant growth and inproved the overall plant nutritional status. The findings of this study will be useful in the development of a low cost technology to manage acid soils found in tropical region. This information will be used by farmers, research organizations and governmental agencies.
Technical Abstract: This study aimed to: a) determine the effect of P depletion and presence of Al on root and shoot growth of representative cover crops, and on their nutrient uptake; b) characterize the composition of root exudation under P and Al stress in nutrient solution; c) evaluate the ability of aqueous extracts of composts in reducing Al phytotoxicity. Plants of cowpea (Vigna unguiculata subsp. Unguiculata), black oat (Avena strigosa), and lablab (Lablab purpureous) were cultivated in different nutrient solution compositions and concentrations for 3 weeks. It was found that Al at concentration of 20 and 200 µmol/L increased citrate exudation at least 8 and 24 times, respectively, for cowpea and 18 and 36 times, respectively, for lablab, as compared with the blank. However, no release of organic acids occurred due to P deprivation, suggesting that citrate exudation was a specific response to excess Al. No response in organic acid release was observed for black oat under the stress of P deficiency or Al toxicity. Although the presence of Al in solution did not significantly affect chlorophyll content in leaves, it decreased root and shoot weight, as well as root length, surface area, volume, and number of tips. Organic extracts alleviated aluminum toxicity, improving plant growth and ameliorating plant nutrition status. Yard waste extract was more effective in enhancing plant growth than GreenEdge extract in plants under Al stress.