Location: Sustainable Perennial Crops Laboratory2015 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.
Sustainable cacao production in the Andean region of South America is being affected severely by increasing abiotic stresses such as drought due to lack of rains, high light due to loss of shade trees and low fertility of the soil. 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 Non Assistance Cooperative Agreement (NACA) to develop sustainable production systems for tropical tree crops and assess 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). This research will assist in the identification of abiotic stress tolerant genotypes. Field experiments were completed at two different plantations that vary in their age, to determine the effectiveness of controlled released fertilizer on cacao production. In both plantations various fertilizers (controlled and regular formulations) did not have any significant effects on yields or on disease intensities. Progress was made (Objective 2A) to evaluate the effects of 10 years of cover crop residue incorporation on the performance of cacao genotypes. Initial soil samples collected from these field studies are being evaluated for soil quality assessments. 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. At the end of the 8th year, soil samples were collected and analyzed for physical, chemical and biological soil quality assessments at ARS-Sustainable Agricultural Systems laboratory (SASL) in Beltsville, Maryland, University of Florida, Indian River Research Education Center (IRREC), Fort Pierce, FL and at the Tropical Crop Research Institute (ICT), Tarapoto, Peru. Field studies established at ICT, continue to evaluate cacao genotypic performance for growth, diseases and insect intensities, and yield. Improved canopy management and phytosanitory practices have been imposed on these field experiments. 305 C1 PS1C 2013-18 & 301 C1 PS1A 2013-17 In the Atlantic region of Brazil, there is a lack of suitable cacao genotypes adapted to various prevailing abiotic stresses and lack of proper management systems are preventing the development of sustainable cacao management systems. Collaborative research under NACA 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 has been implemented to evaluate the cacao genotypic and cover crop species response to abiotic stresses (drought, light, elemental toxicities and deficiencies) and the effects of cacao agroforestry management on soil quality factors. Progress was made to understand the role of anthocyanins (Objective 1B) during molecular and morpho-physiological responses to variations in light levels of cacao genotypes with differing anthocyanin contents. Substantial progress under Objective 1C was made to understand plant growth and nutrient uptake that could help to identify drought tolerant cacao genotypes under greenhouse conditions. Drought tolerant genotypes identified in greenhouse study were crossed in a diallel scheme and progenies of these are being evaluated at the Fazenda Juliana farm for their performance. Under Objective 2.A, substantial progress was made to complete the research on cover crop and cacao genotypes response to zinc. 305 C1 PS1C & 301 C1 PS1A 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. Progress has been made to address Objective 1 in collaborations with a scientist of USDA-ARS Tropical Research Station, Mayaguez, Puerto Rico, through the assessment of cacao genotypic responses to soil acidity. The third year of a field study is being concluded to evaluate selected elite cacao genotypic response to varying levels of soil acidity. In this study, data is being collected on plant growth traits such as shoot and roots growth parameters and soil acidity tolerance index to assess the range of soil acidity tolerance among cacao genotypes. Plant and soil samples are being analyzed at Mayaguez to determine the chemical composition in various plant tissues. 301 C1 PS1A Under Objective 1A and C, scientists at the Beltsville Agricultural Research Center (BARC), Maryland are studying the growth, and physiological plant traits to identify cacao genotypes tolerant to abiotic stresses. A growth chamber study with three cacao genotypes that differ in their tolerance to acid soil were evaluated for their response (growth, physiology and metabolites) to deficient and adequate soil moisture and to adequate and excess lighting. Also at BARC, research was completed to assess the influence of soil potassium levels on macro and micro nutrient uptake parameters and use efficiency in cacao genotypes. 301 C1 PS1A Understanding of plant nutrient status under abiotic stresses and changes of soil quality factors under different cacao management systems is critical to correct soil fertility limitations and formulation of fertilizer management practices to achieve sustainable high yielding cacao production. Collaborative research is being undertaken with scientists from the University of Florida Indian River Research and Education Center (IRREC) Fort Pierce, Florida, under a NACA. Under Objective 1, 2 and 3 considerable progress was made to evaluate elemental composition of tropical crops subjected to abiotic stresses and soil chemical quality parameters of tropical soils under different cacao management systems. Furthermore, in this collaboration substantial progress was made to understand the soil cadmium chemistry, and nature of plant available cadmium in soils of cacao plantations in Peru and Ecuador. From Southern Ecuador soil samples were collected under selected cacao plantations and were evaluated for: (1) concentration of cadmium in cacao beans and its relationship with soil cadmium levels and (2) chemical speciation of soil cadmium: An approach to evaluate plant-available cadmium in Ecuadorian soils under cacao production. 305 C1 PS1C.
1. Molecular, physiological and biochemical response of cacao genotypes under soil water deficit. Frequent occurrence of long periods of drought in the cacao growing regions of South and Central America is severely affecting the yield potentials and health of the cacao trees. Planting of drought tolerant cacao types could help to alleviate the situation. This research identified molecular, physiological and biochemical responses of different cacao genotypes to soil water stress. Methods developed in this research could be useful in identifying drought tolerance in cacao genotypes. Information gained from this research could be useful to plant physiologists in identification of drought tolerant cacao genotypes and plant breeders in selection of drought tolerant crossing materials to breed drought tolerant cacao cultivars.
2. Zinc requirements of tropical legume cover crops. Soil and nutrient loss by erosion and leaching and weed infestations are the major soil degradation factors in reducing crop yield potentials in tropical regions. Cover crops are important components of plantation and row crops cropping systems because improve vegetative cover thereby reducing nutrient loss by erosion and suppressing weed infestations. Success of cover crops in acidic infertile tropical soils is influenced by the level of zinc in the soil with cover crop species having high zinc efficiency possibily producing higher yields and persisting longer when grown on infertile soils where the supply of zinc is limited. An ARS scientist in Beltsville, Maryland, identified interspecific differences in perennial legume cover crops for growth and zinc use efficiency at deficient to adequate levels of soil zinc levels in tropical acidic soils. Zinc efficient cover crops enhanced vegetative ground cover in early stages of plantation crop establishment thereby preventing nutrient loss by erosion, improving soil fertility, suppressing weed infestation and increasing yield potentials of crops. This information could be useful for row crop and plantation crop growers in selection of cover crops that will grow best in zinc deficient or zinc rich soils.
Santosdos, I.C., Anhert, D., Conceicaoda, A.S., Pirovani, C.P., Pires, J.L., Valle, R.R., Baligar, V.C., Almeidade, F.A. 2014. Molecular, physiological and biochemical responses of Theobroma cacao L. genotypes to drought. PLoS One. 9(12):e115746. DOI:10.1371/journal.pone.0115746.
Baligar, V.C., Fageria, N.K. 2014. Nutrient use efficiency in plants: An overview. In: Rakshit, A., Singh, H.B., Sen, A., editors. Nutrient Use Efficiency: from Basics to Advances. New Delhi, India, Springer Publications. p. 1-14.
Fageria, N.K., Baligar, V.C., Heihemann, A.B., Carvalho, M.C. 2014. Nitrogen uptake and use efficiency in rice. In: Rakshit, A., Singh, H.B., Nutrient Use Efficiency: From Basics to Advances, New Delhi, India, Springer Publications, p. 285-296.
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.
Li, Y., Elson, M.K., Zhang, D., He, Z., Sicher Jr, R.C., Baligar, V.C. 2015. Macro and micro nutrient uptake parameters and use efficiency in cacao genotypes influenced by deficient to excess levels of soil K. International Journal of Plant and Soil Science. 7:80-90.