|HE, Z - University Of Florida|
|FAGERIA, N - Embrapa|
|DE SOUZA, JUNIOR - University Of Santa Cruz - Brazil|
|ALMEIDA, A-A - University Of Santa Cruz - Brazil|
|AHNERT, D - University Of Santa Cruz - Brazil|
Submitted to: Journal of Plant Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/23/2015
Publication Date: 9/15/2015
Citation: 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.
Interpretive Summary: In tropical regions, cacao is grown on highly weathered soils where iron deficiency is the major micro nutrient responsible for reduction of yields. Iron is an essential nutrient required for many physiological and biochemical processes in plants. It is important to select the right source of iron to improve stability in soil and its availability to cacao. Better understanding of the effectiveness of different iron source fertilizers on growth, photosynthesis, content of pigments and starch of young cacao can help to increase cacao yields. In this paper we report that various iron sources had significant effects on the growth and physiology of cacao and these parameters were significantly correlated with concentration, uptake, influx, transport and use of iron. Overall, a form of iron called chelated iron is the best sources of iron for the growth of cacao. This information will be useful in nutrient management to avoid iron nutrient deficiency in cacao plantations. Farmers, scientists and extension workers in cacao growing regions will benefit from this research.
Technical Abstract: Productivity and sustainability of cacao (Theobroma cacao L.) in tropical soils are affected by deficiency of micronutrients. Iron deficiency is one of the main yield limiting constraints, especially in highly weathered, coarse textured and leached soils. To correct iron deficiency, different forms of Fe fertilizers have been developed to improve Fe availability to plants in various types of soils. Information is lacking on the cacao response to various sources of Fe. A greenhouse experiment was conducted to evaluate the effects of five iron sources (FeSO4·7H2O, FeEDDHA, FeDTPA, FeEDTA, FeHEDTA) at 10 mg Fe kg-1 soil on growth, photosynthesis, content of photosynthetic pigments and starch and macro and micronutrient nutrition of cacao. The various iron sources had significant effects on shoot and root dry biomass accumulation, leaf chlorophyll a and b content, carotenoid levels, SPAD index and PN. These parameters were significantly correlated with concentration, uptake, influx, transport and use efficiencies of Fe. In cacao net photosynthesis, stomatal conductance, internal CO2, and transpiration in leaf level responded differently to the sources of Fe. Invariably, macro and micronutrient uptake, influx, transport, and use efficiency showed differential responses to sources of iron but significant effects were only observed for Cu, Fe, Mn, and Zn. Overall, FeDTPA, FeEDTA and FeHEDTA could be the best sources of Fe in improving, growth, photosynthesis and macro and micro nutrition of cacao.