Location: Sustainable Perennial Crops Laboratory2017 Annual Report
The overall goal of this project is to develop sustainable management systems to improve the productivity and sustainability of cacao (Theobroma cacao L) 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. [NP 301, C1, PS 1A] Sub-objective 1A: Evaluate and identify cacao genotypes with superior tolerance to soil acidity. Sub-objective 1B: Determine key physiological and growth responses of selected cacao genotypes under different levels of irradiance (shade). Sub-objective 1C: Evaluate and identify selected cacao genotypes with superior drought tolerance. Objective 2: Characterize and manage soil nutritional components essential for optimal cacao yields. [NP 305, C1, PS 1C] Sub-objective 2A: Determine the residual effects of cover crops with and without NPK fertilizers on production potentials and bean quality. Sub-objective 2B: Determine the effectiveness of controlled release fertilizer formulations on improving growth, production, and cocoa bean quality of selected cacao genotypes grown in specific soil types. Sub-objective 2C: Determine optimum concentrations and nutrient use efficiencies of macro and micro-nutrients in selected cacao genotypes. Objective 3: Develop environmentally sustainable cacao management systems that improve soil quality and yield. [NP 305, C1, PS1C] Sub-objective 3A: Integrate improved canopy management, phytosanitation, and other management practices into cacao field experiments to evaluate their combined effect on yield. Sub-objective 3B: Develop an improved cacao rejuvenation system that integrates improved management practices and evaluates its effect on cacao yield.
The major emphasis of this project is to identify cacao genotypes tolerant to abiotic stresses (drought, infertile acidic soils, and high/low irradiance) and develop sustainable management systems to improve their productivity and bean quality. The residual effects of cover crop cultivation and improved management systems (agroforestry planting, high density planting, fertilization, sanitary and phyto-sanitary practices) on the changes of soil quality parameters (physical, chemical, biological) and bean yield and quality will also be determined. Nutrient use efficiency of macro-micronutrients of elite cacao genotypes and cover crops at various abiotic stresses and management systems will be evaluated. Enhanced nutrient use efficiency and sustainable high productivity of cacao will be achieved through improved management practices. To achieve these objectives we have established collaborative research programs under specific cooperative agreements with government and non-government organizations (NGO) and national and international agricultural universities in cacao growing regions of Peru, Brazil, and Ecuador, and the University of Florida at Fort Pierce as well as the USDA ARS in Puerto Rico to establish controlled studies in greenhouses and large scale field trials. University of Reading (UR), UK will be collaborating on abiotic stress assessment. 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 further soil degradation.
Collaborative research was undertaken with scientists from the Tropical Crop Research Institute (ICT) in Tarapoto, Peru and National University of Agraria La Molina (UNALM) Lima, Peru under a funded agreement to develop sustainable production systems for tropical tree crops and assess cacao germplasm to improve cacao sustainability under various abiotic stresses. Progress was made toward Objectives 1.A, B, and C to assess the performances of cacao varieties or genotypes collected from various Peruvian river basins, national and international cacao genotypes to abiotic stresses (drought, soil acidity, and light quality) and soil cadmium toxicity. Various morphological, physiological plant traits have been recorded and plant samples have been submitted for macro-micronutrient analysis. This research is focused around the identification of abiotic stress tolerant genotypes. Progress was made (Objective 2A) to evaluate the effects of 10 years of cover crop residue on cacao genotypes performance and the soil samples have been collected and are being analyzed to evaluate soil quality factors. Substantial progress was made to address Objective 3A through long term field studies that have been established to evaluate cacao genotypic responses to different agroforestry management systems. Data was compiled on soil physical and chemical quality factors. Overall soil nutrient status was much higher in the improved traditional agroforestry system than in improved natural agroforestry systems. Therefore success of sustainable cacao production systems in the Peruvian Amazon areas is dependent on the proper management of the physical and chemical properties of these soils. In collaborations with ARS scientists in Beltsville, Maryland, the effects of long term cacao genotypes management and the influence of cover crops on soil biological quality factors were analyzed. In tropical agroforestry systems microbial community structure was significantly affected by management systems and cover cropping (Objective 3A). Long term field studies continue to evaluate cacao genotypic performance for growth, diseases and insect intensities, and yield under different agroforestry systems. Improved canopy management and phytosanitory practices have been implemented on these field experiments. A clonal garden has been established to evaluate wild cacao accessions collected from the Amazon River basins of Peru and Common Fund for Commodities (CFC) clones from the University of Reading, United Kingdom. Seedlings of different clones are being prepared for field evaluation and green house studies. Studies on heavy metal accumulations in leaves and beans of cacao in major cacao growing regions of Peru was completed. The mean values of heavy metals with the exception of cadmium in leaf and bean samples were below the critical limits; however high levels of cadmium in beans were found in some cacao growing regions of Peru. Collaborative research conducted through a funded agreement was undertaken with scientists from the State University of Santa Cruz (UESC), and Cacao Research Institute (CEPLAC/CEPEC) Bahia, Brazil to assess the cacao genotypic response to abiotic stresses (drought, light, elemental toxicities and deficiencies) and to evaluate the effects of the cabruca cacao agroforestry management systems on soil quality factors. Progress was made in the evaluation of cacao genotypes response to (1) flooding under low light intensities, (2) soil potassium levels, (3) drought and (4) toxic levels of cadmium (Objective 1A, B, C). Morphological and physiological plant traits and root plasticity were evaluated. The root volume was the growth variable most influenced by the change in water regime. Cacao quality index and biochemical attributes of cacao beans were evaluated from different agroecosystems. Cacao quality indexes and biochemical attributes of cacao beans were evaluated from different agroecosystems and the cacao system that utilized rubber as the shade tree on Latosol Red-Yellow soil showed the best quality characteristics in dry cacao beans. (Objective 3A). Substantial progress has been made to address Objective 1A in collaborations with ARS researchers in Mayaguez, Puerto Rico to assess soil acidity complexes on the performance of different cacao genotypes. The third year of a field study was completed and data was collected on plant growth traits and soil acidity tolerance indexes to assess the range of tolerance among the tested cacao genotypes. Plant and soil samples have been submitted to determine the chemical composition. Further progress was made studying the response of cacao genotypes from South America and Puerto Rico to abiotic stresses such as drought, low light, and elevated carbon dioxide. A growth chamber study with two cacao genotypes (Hybrid 27-1420, Amelonado) from Puerto Rico differing in acid soil tolerance were evaluated for their response (growth, physiology and biochemical) to adequate and deficit soil moisture levels. Plant samples were prepared for determination of nutrient composition. In collaborations with the Adaptive Cropping System Laboratory at Beltsville, Maryland, metabolites compositions in cacao leaf samples were completed. Water and nutrient use efficiency, drought tolerance indexes, growth and physiological parameters are being determined. To achieve sustainably high yielding cacao production it is essential to understand the nutrient status of plants subjected to abiotic stresses under different management systems. Changes to soil quality factors under different cacao management systems are critical to correct soil fertility limitations and to formulation of fertilizer management practices. Considerable progress was made though collaborative research undertaken with scientists from the University of Florida Indian River Research and Education Center (IRREC) Fort Pierce, Florida, under a funded agreement to evaluate nutrient use efficiency of cacao genotypes subjected to abiotic stresses (Objective 1). Changes in the elemental composition of macro (nitrogen, phosphorus, potassium, calcium, magnesium) and micronutrients (boron, copper, manganese, iron, zinc) of different cacao genotypes are being analyzed as a response to deficit soil moisture levels.
1. Ambient and elevated carbon dioxide and low light on growth, physiological and nutrient uptake parameters of perennial tropical leguminous cover crops. In the tropics, soil degradation is a major cause of poor plantation crop establishment and low productivity. Inclusions of quick growing legume cover crops during the early establishment of tropical plantation crops reduce soil degradation due to erosion and nutrient leaching. Adaptability and optimum growth of cover crops in plantation crops is affected by the inherent nature of the cover crop species and the light intensity at canopy levels. Global concentrations of atmospheric carbon dioxide are increasing and have an implication on crop growth. A better understanding of required light intensity in these changing carbon dioxide levels will help in increasing the success of cover crops utilization in plantation crops. The growth and essential nutrient uptake parameters of five important perennial tropical legume cover crops (Calopo/frisolla, Jack bean, Brazilian Lucerne, Leucaena, and Mucuna) were analyzed and were found to be significantly influenced by light intensity and by the carbon dioxide level. Brazilian Lucerne and Jack bean were more efficient in nutrient use efficiency of nitrogen, potassium, magnesium, copper, iron, and manganese, while Calopo and Leuacena were more efficient in zinc use efficiency and Leucaena was more efficient in potassium use efficiency under elevated carbon dioxide levels. Overall, the total growth parameters measured were significantly influenced by the higher carbon dioxide levels. This information allows farmers, extension specialists and researchers to select the appropriate tropical cover crops to reduce soil degradation and improve soil fertility and crop yields.
Baligar, V.C., Fageria, N.K. 2017. Nitrogen forms and levels influence on growth and nutrition of cacao. Journal of Plant Nutrition. 40:709-718.
Baligar, V.C., Elson, M.K., He, Z.L., Li, Y.C., Paiva, A.D., Ahnert, D., Fageria, N.K. 2017. Ambient and elevated carbon dioxide on growth, physiological and nutrient uptake parameters of perennial leguminous cover crops under low light intensities. International Journal of Plant and Soil Science. 15:1-16.
Nkengafac, N., Baligar, V.C. 2016. Soil physical and chemical properties of cacao farms in the south western region of cameroon. International Journal of Plant and Soil Science. 16:1-10.
Arevalo-Guardini, E., Cerpa, M., Cernades, L., Baligar, V.C., He, Z. 2016. Heavy metals in soils of cocoa plantation (Theobroma cacao L.). Journal of Applied Ecology. 15:81-89.
Silva Branco, M.C., Almeida, A.A., Dalmolin, A.C., Ahnert, D., Baligar, V.C. 2017. Influence of low light intensity and soil flooding on cacao physiology. Scientia Horticulturae. 217:243-257.
Chavez, E., He, Z.L., Stoffella, P., Mylavarapu, R., Li, Y., Baligar, V.C. 2016. Evaluation of soil amendments as a remediation alternative for cadmium contaminated soils under cacao plantations. Environmental Science and Pollution Research. 23:17571-17580.
Santos, E.A., Almeida, A.A., Ahnert, D., White, M.C., Valle, R.R., Baligar, V.C. 2016. Diallel analysis and growth parameters as selection tools for drought tolerance in young Theobroma cacao plants. PLoS One. doi:10.1371/journal.pone.0160647.