Location: Sustainable Perennial Crops Laboratory2016 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.
In the Andean region of South America increasing abiotic stresses such as drought due to lack of rains, high light due to loss of shade trees and low soil fertility due to soil degradation are severely affecting the sustainable production of cacao and other economically valuable tree crops. Collaborative research was undertaken with scientists from Tropical Crop Research Institute (ICT) in Tarapoto, 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). Various morphological and physiological plant traits have been assessed. Leaf samples have been collected for determination of elemental content. This research will assist in the identification of abiotic stress tolerant genotypes. Progress was made (Objective 2A) to develop a soil fertility study in an area where various cover crops were grown for 10 years and where cover crop residue were incorporated into the soil. Fertilizers have been applied and the soil samples have been collected and are being analyzed for evaluation of soil quality factors. Substantial progress was made to address Objective 2B through a long duration, field experiments to determine the effectiveness of controlled released fertilizer on two systems of cacao production. Experiments were completed and data are being compiled. Substantial progress was made to address Objective 3A through long term field studies that have been established to evaluate cacao genotypic responses to Andean and agroforestry management systems. Soil physical and chemical quality factors of soil samples from the 8th year were completed at the University of Florida, Indian River Research Education Center (IRREC), Fort Pierce, Florida and at the Tropical Crop Research Institute (ICT), Tarapoto, Peru. Surface soil biological components of these soil samples are being assessed at ARS-Sustainable Agricultural Systems Laboratory in Beltsville, Maryland. Diversity of soil fungal communities in this field study was completed. Long range field studies established at ICT, continue to evaluate cacao genotypic performance for growth, diseases and insect intensities, and yield in different agroforestry systems. Improved canopy management and phytosanitory practices have been imposed on these field experiments. In the Atlantic region of Brazil, frequent occurrence of drought, low light quality at the crop canopy level, soil infertility and lack of proper management systems are preventing the development of sustainable high production cacao management systems. Furthermore, a lack of suitable cacao genotypes adapted to various prevailing abiotic stresses is affecting the cacao improvement program for the region. Collaborative research was undertaken with scientists from State University of Santa Cruz (UESC), Brazilian Cacao Research Institute (CEPLAC),and Institute Cabruca, Bahia along with the National Rice and Bean Center of Empresa Brasileira de Pesquisa Agropecuária (EMBRAPA), Santo de Antonio, GO, Brazil in a funded Agreement that has been implemented to evaluate the cacao genotypic and cover crop species response to abiotic stresses (drought, light, elemental toxicities and deficiencies) and to evaluate the effects of cacao agroforestry (cabruca) management systems on soil quality factors. Progress was made in the evaluation of leaf pigments on photoinhibition, leaf anthocyanins contents provided no protection against photoinhibition in cacao accessions (Objective 1B). Substantial progress was made (Objective 1C) in using growth parameters (stem diameter and biomass, root biomass and length, total dry biomass) as selection tools for drought tolerance in young cacao plants derived from hybrid crosses of varying drought tolerant cacao accessions. Progress was made (Objective 2C) to evaluate the mineral element composition (essential, non essential, toxic) of dried cacao beans of PH 16 grown under different agroforesty management systems in Bahia Brazil. Influence of soil zinc levels on growth and nutrition of the cacao clone PH 16 in three acidic oxisol soils was completed (Objective 2C). Soil acidity complexes (low pH, deficiency of essential nutrients, toxicities of Mn and Al) are major growth limiting factors for cacao in low fertility soils of the tropics. Substantial progress has been made to address Objective 1A in collaborations with a USDA-ARS scientist from the Tropical Research Station, Mayaguez, Puerto Rico, through the assessment of cacao genotypic responses to soil acidity. The third and final year of a field study to evaluate selected elite cacao genotypic response to varying levels of soil acidity was concluded. In this study, data were collected on plant growth traits such as shoot and roots growth parameters and soil acidity tolerance index to assess the range of tolerance among the tested cacao genotypes. Plant and soil samples are being weighed to determine biomass accumulation and the samples will be further analyzed to determine the chemical composition in various plant tissues. Under Objective 1A and C, scientists at the Beltsville Agricultural Research Center in Beltsville, Maryland are studying the response of cacao genotypes from South America and Puerto Rico to abiotic stresses such as drought, low light, and elevated CO2. A growth chamber study with three cacao genotypes from CEPLAC and UESC Bahia, Brazil differing in drought tolerance were evaluated for their response (growth, physiology and biochemical) to adequate and deficit soil moisture levels. Plant samples were prepared and determination of nutrient composition for macro and micronutrients were completed. In collaborations with Crop Systems Global change 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. In collaborations with scientists from Institute of Agriculture Research for Development (IRAD) of Cameroon, soil fertility status assessments for cacao farms from the South-Western region of the country were completed. 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 fertilizer management practices. Collaborative research is being undertaken with scientists from the University of Florida Indian River Research and Education Center (IRREC) Fort Pierce, Florida, under a funded agreement. Under Objective 1, 2 and 3 considerable progress was made to evaluate elemental composition of macro (N, P, K, Ca, Mg) and micronutrients (B, Cu, Mn, Fe, Zn) of cacao grown in field and controlled conditions. Furthermore, in this collaboration research evaluations of the cadmium status in soil-plant systems of Southern Ecuador was conducted. Soil samples were collected under selected cacao plantations and were evaluated for various forms of soil cadmium, the levels of Cd in cacao beans and their relationship with soil cadmium levels.
1. Effects of different forms of iron on cacao nutrition and physiology. Cacao is grown on highly weathered acidic infertile Oxisols and Ultisols and in these soils iron (Fe) deficiency is one of the major nutrient responsible for reduction of yields and its sustainability. It is important to select the right source of Fe to improve its stability and availability to cacao in these acidic infertile soils. ARS scientists in Beltsville, Maryland reporting that right sources of iron fertilizers have significant effect on growth, photosynthesis, and nutrient uptake parameters of young cacao plants. Chelated forms of Fe are the best sources of Fe for improving growth, and physiological traits of cacao. This information will be useful in nutrient management to avoid iron nutrient deficiency and for improved sustainable production systems for cacao. Farmers, scientists and extension workers who need to develop improved nutrient management systems for infertile acidic soils will benefit from this research.
2. Long-term agroforestry cacao management systems have effects on soil quality. Slash and burning of native vegetation and planting of cacao is a traditional management system adopted by the farmers of the Peruvian Amazon region which leads to soil degradation and deforestation of native forest flora. For the first time ARS scientists in Beltsville, Maryland, are reporting the impact of long-term improved natural agroforestry systems (INAS) and an improved traditional agroforestry system (ITAS) of cacao management on soil physical and chemical properties in an area planted with different cacao accessions. Our results indicate that management practices have tremendous impact on soil properties. In both systems, soil organic matter, extractable phosphorous and exchangeable cations increased with years of cultivation. Therefore success of sustainable cacao production systems in the Peruvian Amazon is dependent on the proper management of the physical and chemical properties of these soils. Findings of this study will be useful to resource poor cacao farmers of the Amazon region to develop cacao management systems that enhance the fertility and productivity of these soils.
3. Zinc effects on the growth and nutrition of cacao in acidic and infertile tropical soils. Levels of Zn in tropical soils profoundly influence the production potentials and nutrition of tree crops such as cacao. Among the micronutrients, zinc (Zn) is one of the most limiting soil nutrients in Oxisols and Ultisols of South America especially where cacao is grown. ARS scientists in Beltsville, Maryland reporting that the growth and essential mineral nutrient levels in cacao genotypes are influenced by both deficient to excess levels of soil Zn in the acidic soils, and at all of the levels of Zn tested, cacao seedlings showed differences for biomass production and for foliar nutrient concentrations of P, K, Ca, Mg, Mn, Fe, Cu, and Zn. Information gained from this research will be useful to researchers, extension workers and farmers to design Zn fertilization practices and to improve sustainability of highly productive cacao in acidic infertile soils.
4. Cadmium (Cd) in cacao leaves and cacao beans and its relationship to soil Cd levels. Soils under cacao in Ecuador contain high levels of Cd. Cadmium poses a threat to food safety and human and plant health around the world. Plants can tolerate Cd concentration at low levels without showing any symptoms of toxicity, but accumulation of Cd in edible plant parts often causes adverse effects on human health. The range of total and extractable Cd in soil profiles of 19 cacao farms were assessed along with the relationship between soil properties and the soil Cd levels. ARS scientists in Beltsville, Maryland reporting that Cd accumulates in the surface soils (0-15 cm) and that 12 out of the 19 sampled sites exceeded the critical level. The distribution of Cd in cacao plants generally decreased in the order of beans > shell >> leaves. This information will be useful to farmers and traders of cacao beans faced with increased regulations to reduce cadmium contaminations.
5. Chemical speciation of soil cadmium (Cd); an approach to evaluate plant available Cd. Cadmium is one of the most plant-available elements in agricultural soils. Cadmium poses a threat to food safety and human and plant health. However there is no information relating to the forms of soil Cd and there bioavailability to plant and its accumulation in cacao beans. ARS scientists in Beltsville, Maryland used soil chemical analytical methods to identify various available Cd pools in the soils and determined relationship of these Cd pools with bean Cd concentration at several sites in Ecuador. The acid-soluble fraction was more closely related to bean-Cd levels. Such information will help scientists and researchers to select suitable chemical extraction method to identify plant available Cd in soils. This information is also useful to farmers either to avoid such areas for cacao cultivation or to find suitable management practices to reduce Cd bioavailability.
The collaborative research projects established under funded agreements with the Instituto de Cultivos Tropicales (ICT) in Tarapoto, Peru and the Fundacao Pau Brasil in Ilhéus, Bahia, Brazil and with State University of Santa Cruz (UESC) are serving as training grounds for undergraduate/graduate students, and many of the regional resource poor farmers and extension workers in best management practices for sustainable cacao production in the Andean region of Peru and Atlantic forest region of Brazil. Many graduate students in Peru, Brazil, Ecuador and U.S. are involved in research carried out under these agreements and are collecting data and conducting experiments to complete their Masters and PhD research.
Chavez, E., He, H.E., Stoffella, P.J., Mylavarapu, R.S., Li, Y.C., Moyano, B., Baligar, V.C. 2015. Concentration of Cadmium in Cacao Beans and its Relationship with Soil Cadmium in Southern Ecuador. Science of the Total Environment. 533:205-214.
Baligar, V.C., Sicher Jr, R.C., Elson, M.K., He, Z., Fageria, N.K., De Souza, J.J., Almeida, A.F., Ahnert, D. 2015. Iron sources effects on growth, physiological parameters and nutrition of cacao. Journal of Plant Nutrition. 38:1787-1802.
Arevalo, E., Canto, M., Alegre, J., Loli, O., Julica, A., Baligar, V.C. 2015. Changes in soil physical and chemical properties in long term improved natural and traditional agroforestry management systems of cacao genotypes in Peruvian Amazon. PLoS One. 10(7):1-29.
He, S., He, Z., Yang, X., Stoffella, P., Baligar, V.C. 2015. Soil biogeochemistry, plant physiology and phytoremediation of cadmium contaminated soils. Advances in Agronomy. 134:134-225.
Cruz Neto, R.O., Souza Junior, J.O., Sodre, G.A., Baligar, V.C. 2016. Growth and nutrition of cacao seedlings influenced by zinc application in soil. Revista Brasileira de Fruticultura. 37:1053-1064.
Chavez, E., He, H.E., Stoffella, P.J., Baligar, V.C. 2016. Chemical speciation of cadmium: an approach to evaluate plant-available cadmium in Ecuadorian soils under cacao production. Geoderma. 150:57-62.
Fageria, N.K., Baligar, V.C. 2016. Growth, yield and yield components of dry bean as influenced by phosphorus in a tropical acid soil. Journal of Plant Nutrition. doi: 10.1080/01904167.2016.1143489.
Barnaby, J.Y., Fleisher, D.H., Baligar, V.C., Reddy, V., Sicher Jr, R.C. 2015. Effects of CO2 enrichment and drought pretreatment on metabolite responses to water stress and subsequent rehydration using potato tubers from plants grown in sunlit SPAR chambers. Journal of Plant Physiology. 189:126-136.