Location: Sustainable Perennial Crops Laboratory2012 Annual Report
1a. Objectives (from AD-416):
The goal of this project is to develop sustainable management systems to improve the productivity and sustainability of cacao cultivation. To accomplish this goal the following objectives will be addressed. Objective 1: Identify cacao genotypes with superior ability for establishment under conditions of environmental stress. Objective 2: Evaluate effects of tropical legume cover crops on factors affecting yield of cacao. Objective 3: Characterize and manage soil nutritional components essential for optimal cacao yield. Objective 4: Develop improved cacao crop management systems that maintain or improve environmental conditions.
1b. Approach (from AD-416):
The goal of this project is to identify cacao genotypes with superior ability for establishment under prevailing environmental stresses, and to develop sustainable management systems to improve the productivity and sustainability of cacao cultivation. Leguminous cover crops in early cacao establishment can protect soil from degradation by erosion and prevent weed infestation; therefore the influences of shade, soil acidity and micronutrients on growth and development of cover crops will be determined. Influences of cacao and cover crop management practices on changes of soil quality parameters (physical, chemical, biological) and nutrient components essential for maximum cacao production will be determined. Work will be conducted in controlled environmental chambers, greenhouses and field plots. We have developed collaboration with government and non-governmental research institutes, and universities in Peru, Brazil, Puerto Rico, and Ecuador to establish large scale field trials. Cacao genotypes with superior ability for establishment under abiotic stresses will be identified and incorporated in cacao improvement programs. Improved management systems will be developed, based on the results of this research, to enhance cacao yield potentials and bean quality and further improve soil fertility and halt the soil degradation.
3. Progress Report:
In FY 2012, progress was made in implementation of field research at the Tropical Crop Research Institute (ICT) in Tarapoto, Peru in establishing a clonal cacao garden to evaluate the performance of national and international cacao genotypes. International cacao clones from University of Reading, UK have been transferred to ICT, Peru and these clones and wild clones collected from the Peruvian Amazon river basins are being established in the clonal gardens for further evaluations. At this location long term field study has been established to evaluate cacao genotypic response to management. Soil quality parameters are being determined and related to bean production and quality. In collaboration with scientists of USDA-ARS Mayaguez, Peru, a field study is being established to evaluate cacao genotypic response to varying levels of soil acidity. In collaborative work at the State University of Santa Cruz (UESC) Bahia, Brazil under a specific cooperative agreement, greenhouse experiments are being conducted to assess the selected cacao genotypes response to drought and micronutrients. We collaborated with scientists from Brazilian Cacao Research Institute (CEPLAC) and the State University of Santa Cruz (UESC) in Bahia, Brazil under a Specific Cooperative Agreement to evaluate the relationship between soil quality and bean quality in 15 cacao management systems. At the initial stages of cacao establishment, soil is subjected to degradation due to soil loss by erosion and leaching. Providing vegetative cover by use of legume cover crops could reduce soil degradation processes and improve soil fertility. However, persistence of cover crops is controlled by the quality of light. At Beltsville, MD a greenhouse experiment was carried out to evaluate three light intensity effects on growth and physiological traits of 9 legume cover crops. Growth and physiological parameters and chemical composition of macro and micronutrients are being determined. In growth chambers, three cacao genotypes (Amelonado, EET 400, ICS 95) were evaluated for deficient and excess levels of potassium at Beltsville, MD. Plant chemical compositions for macro-micronutrients are being determined at University of Florida Indian River Research and Education Center (IRREC) under a Specific Cooperative Agreement. In Ecuador, selection of national hybrid clones needed for grafting on existing trees was completed and farmers are being selected to implement field research.
1. Agroforestry system improves carbon sequestration in soils under cacao. Cacao is a shade tolerant plant and is invariably grown as an understory plant in agroforestry systems. Under such systems of management maintenance of soil organic carbon is vital for better soil quality and higher cacao productivity. An increased understanding of the nature of soil organic matter that has different susceptibility to microbial decomposition could help in the management of soil carbon dynamics in agroforestry systems. In collaboration with scientists at the State University of North Fluminense (UENF), Campos RJ, Brazil field research in Bahia Brazil was carried out under a Specific Cooperative Agreement to evaluate carbon sequestrations in various cacao agroforestry systems. This work established that in agroforestry system with cacao production on highly weathered soils, physical protection of organic carbon within macroaggregate (large soil particles) appears to be the main mechanisms of carbon stabilization. This is a very important finding because it shows that microaggregates play a significant role in carbon stabilization in highly weathered tropical soils. This information will be of use to farmers, scientists and policy makers who need to improve carbon sequestrations in highly weathered degraded tropical soils under perennial tropical tree crops.
2. Light, temperature and carbon dioxide influence photosynthesis of the legume cover crop, crotalaria. Perennial legume cover crops grown as understory plants in cacao plantations could improve soil quality and suppress weeds. However, survivability and persistence of understory cover crops depends largely on the amount and quality of light reaching their canopies. This research was carried in collaborations with scientists from government and non government and universities in Peru and Brazil. Research was undertaken in a climatically controlled growth room to evaluate the effects of light intensity, external temperature, and carbon dioxide concentrations on the rate of photosynthesis in four crotalaria cover crop species. Increasing light intensity, temperature and carbon dioxide enhanced photosynthesis in all the crotalaria species. This is an important finding because it shows the amount of shade and associated temperature can have a significant impact on the growth, survivability and effectiveness of crotalaria cover crops in plantation crops. These findings show that canopy management of overstory trees to increase light levels is very critical to maintain the persistence and productivity of crotalaria as a cover crop in cacao plantations. Findings of this study could assist cacao farmers to develop shade management systems to improve growth and persistence of crotalaria cover crops to enhance soil fertility and there by improve cacao productivity in degraded tropical soils.
3. Reclaimed water could be useful for irrigation of tree crops in drought prone areas. Success of perennial crops under prolonged drought depends on providing supplemental irrigation. Reuse of urban reclaimed wastewater (RWW) appears to be an attractive alternative where availability of fresh water is a problem. Even though RWW is a good source of plant essential nutrients, concerns remain regarding its effects on soil quality. Field research was undertaken under a Specific Cooperative Agreement with the University of Florida Indian River Research and Education Center, Fort Pierce, FL to evaluate long term effects of RWW as compared to well water (WW) on soil quality under citrus trees. Although RWW irrigation affected the majority of evaluated soil quality parameters, the risk of negative impact from RWW irrigation on soil quality appears to be minimal. In years of prolonged drought supplemental irrigation of perennial crops with RWW appears to be beneficial in saving the crops from drought damage and additional benefits include saving fresh water and fertilizer cost. Findings of this study are very useful to sustain the productivity of perennial crops in areas where droughts are occurring very frequently thereby keeping steady economic returns for resource poor farmers of tropical region. This information will be used by researchers, agronomists, physiologists, extension personnel, and farmers who are developing and using methods to reduce the impact of drought on cacao.
4. Dry bean genotypes tolerant to soil acidity are good cover crops on degraded soils. Soil acidity and low soil fertility are the major constraints for crop production in the tropical regions of the world. Soil acidity is a major yield limiting factor for bean production in the tropical regions. Using soil acidity tolerant genotypes is an important strategy in improving bean yields and reducing the cost of production. Greenhouse research was implemented under a Specific Cooperative Agreement with the National Research Center for Rice and Bean (CNPAF) from the Brazilian Government Research Organization (EMBRAPA), to assess the differential acidity tolerance among dry bean genotypes. In acid soils, dry bean genotypes differed significantly in shoot weight and grain yield. Furthermore, a soil acidity tolerance index based on grain yield differentiated the range of acidity tolerance among bean genotypes. Acid soil tolerant genotypes identified in this research will be useful in the development of high yielding bean cultivars for acid infertile soils of South America. Such bean cultivars could help to reduce costly inputs such as lime and fertilizers for the resource poor farmers of the tropics and useful as effective cover crops to improve degraded infertile acidic soils found throughout the tropics.
Fageria, N.K., Baligar, V.C., Meio, L.C., De Oliveira, J.P. 2012. Differential soil acidity tolerance of dry bean genotypes. Communications in Soil Science and Plant Analysis. 43:1523-1531.