Location: Sustainable Perennial Crops LaboratoryTitle: Zinc requirements of tropical legume cover crops
Submitted to: American Journal of Plant Sciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/21/2014
Publication Date: 5/1/2014
Publication URL: http://handle.nal.usda.gov/10113/63026
Citation: Fageria, N.K., Baligar, V.C., Elson, M.K. 2014. Zinc requirements of tropical legume cover crops. American Journal of Plant Sciences. 5:1721-1732.
Interpretive Summary: Nutrient loss by erosion and leaching and weed infestations are major soil degradation factors that reduce crop yield potentials in tropical soils. Cover crops protect the soil thereby reducing nutrient loss by erosion and suppressing weed infestation. However, many cover crops are influenced by the level of zinc in the soil and the response of most cover crops to zinc fertilization in acidic soils of South America is unknown. In this paper we report differences in growth and zinc use efficiency of perennial legume cover crops subjected to deficient and adequate levels of zinc in tropical acidic soils. Jack bean, black velvet bean, kudzu and gray velvet bean were found to have high zinc use efficiency, which would make them suitable cover crops for low zinc soils. These cover crops could be used for ground cover in the early stages of crop establishment, thereby preventing nutrient loss by erosion, improving soil fertility, suppressing weed infestation and increasing yield potentials. This information will be useful for row crop and plantation growers who need to select cover crops that will grow best in zinc deficient or zinc rich soils. This research also provides needed information on managing zinc levels in low fertility tropical soils.
Technical Abstract: Tropical soils are deficient in essential plant nutrients, including zinc (Zn). Using cover crops in cropping systems is an important option to improve soil fertility for sustainable crop production. However, success of cover crops in highly weathered tropical infertile acid soils is greatly influenced by adequate levels of available soil micronutrients. A greenhouse experiment was conducted to evaluate the Zn requirements of ten major tropical legume cover crops. The Zn levels used were 0, 10, 20 and 40 mg kg-1 soil. Overall, shoot and root dry weight and maximum root length increased significantly in a quadratic fashion with increasing Zn rates in the range of 0 to 40 mg kg-1. The Zn X cover crops interactions for shoot and root dry weight, maximum root length, Zn concentration (content per unit dry weight), Zn uptake (concentration X dry weight) and Zn use efficiency (dry weight per unit Zn uptake) were significant, indicating variation in these traits with the change in soil Zn levels. Collectively, maximum shoot dry weight was achieved with the application of 22 mg Zn kg-1 of soil. Similarly, maximum root dry weight and root length were obtained with the addition of 22 and 17 mg Zn kg-1 soil, respectively. Overall, Zn concentration and Zn uptake were significantly increased in a quadratic manner with the increase in the soil Zn levels in the range of 0 to 40 mg kg-1. However, Zn use efficiency (dry weight per unit Zn uptake) decreased in a quadratic fashion with the increasing soil Zn levels from 0 to 40 mg kg-1. Jack bean, black velvet bean, pueraria, and gray velvet bean with high Zn use efficiency appear to be suitable cover crops for low Zn soils.