Evaluation of tropical legume cover crops for copper use efficiency

Authors: FAGERIA, N - Embrapa; Baligar, Virupax

Submitted to: American Journal of Plant Sciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/20/2014
Publication Date: 4/1/2014
Publication URL: https://handle.nal.usda.gov/10113/59058
Citation: Fageria, N.K., Baligar, V.C. 2014. Evaluation of tropical legume cover crops for copper use efficiency. American Journal of Plant Sciences. 5:1236-1247.

Interpretive Summary: In the Andean region, cacao is invariably established on newly cleared forest land. Lack of vegetative cover in early cacao establishment leads to soil degradation due to loss of soil and nutrients by erosion. Establishment of legume cover crops in early stages of cacao planting could prevent further soil degradation. Success of the cover crops in early cacao plantations is dependent on the level of soil micronutrients such as copper. In this paper we report the influence of soil applied copper fertilizer on growth responses, uptake and use efficiency of copper by cover crops. We also report the effects of soil applied copper on chemical properties of an acidic Oxisol soil. At varying soil copper levels, interspecific differences were observed for shoot and root growth, root length, and uptake and use efficiency of copper. Increasing copper levels overall increased growth of cover crop species. Cacao growers can use this information in the selection of cover crops that will grow best in copper deficient or copper rich soils. Efficient cover crops will improve ground vegetative cover in early stages of cacao establishment thereby preventing nutrient loss by erosion, improving soil fertility and increasing yield potentials of cacao plantations. This research also provides needed information on managing copper levels in tropical soils.

Technical Abstract: Cover crops are important components of cropping systems due to their role in improving soil quality. Lack of adequate levels of soil micronutrients prevent the success of cover crops in highly weathered tropical soils. A greenhouse experiment was conducted with the objective to evaluate copper use efficiency of nine tropical legume cover crops. The copper levels used were 0, 5, 10 and 20 mg Cu kg-1 of soil. Shoot dry weight, maximum root length and root dry weight significantly increased in a quadratic fashion with increasing soil Cu levels in the range of 0 to 20 mg kg-1 soil. Cu x cover crops interactions for shoot dry weight, root dry weight, maximum root length and contribution of root to the total dry weight were significant, indicating different responses of cover crops with the variation in soil Cu levels. Overall, maximum shoot dry weight was obtained with the application of 13 mg Cu kg-1. Similarly, maximum root dry weight and maximum root length were obtained with the application of 12 and 14 mg Cu kg-1 of soil. Root dry weight and maximum root length were significantly and positively related to shoot dry weight, indicating a vigorous root system is important for improving productivity of cover crops grown on Brazilian Oxisols, especially where deficiency of micronutrients such as Cu exists. The Cu concentration in the plant tissue decreased in a quadratic fashion whereas, Cu uptake increased with increasing Cu application rates from 0 to 20 mg kg-1 soil. There was a significant variation observed in Cu use efficiency among cover crop species. Increasing applied Cu levels significantly increased soil pH and Mehlich 1 extractable soil Cu, Zn, Mn and Fe concentrations in the soil solution.