Submitted to: American Society of Agronomy
Publication Type: Abstract Only
Publication Acceptance Date: 5/13/2005
Publication Date: 11/6/2005
Citation: Baligar, V.C., Fageria, N., Bunce, J., Machado, R. 2005. Co2 and light intensity on growth and macronutrient uptake of cacao genotypes. American Society of Agronomy. Abstract Interpretive Summary:
Technical Abstract: Invariably cacao(Theobroma cacao L) is grown as an understory plant and is subjected to various levels of shade. In recent years, concentration of [CO2] in the atmosphere has risen to 370 micromol/mol with levels expected to double by the end of 21st century. A climatically controlled greenhouse experiment was undertaken to assess the influence of two levels of [CO2] concentrations (400, 700 micromol/mol -l) and three levels of photosynthetic photon flux density (PPFD, 50, 150, 450 micromol/m-2's-1) on the growth, and uptake, and use efficiency of macronutrients by two cacao genotypes (SCA-6 and TSH-516) in their early growth stage. At all the levels of PPFD, with few exceptions, increasing [CO2] concentrations tended to increase shoot and root biomass accumulations, shoot/root ratio, relative growth rates and net assimilation rates. At both [CO2] concentrations, increasing PPFD from 50 to 450 micromol/m-2/s-1 increased shoot and root growth parameters and net assimilation rates of both the genotypes. At 400 micromol/mol –l [CO2], increasing PPFD enhanced growth of SCA-6 higher than TSH-516, however at 700 micromol/mol -l[CO2], THS-516 performed better than SCA-6 at all levels of PPFD. With some exceptions, in both genotypes increasing [CO2] and PPFD increased the uptake of all the macronutrients (N, K, Ca, Mg, P, S). With few exceptions in both genotypes increasing [CO2] concentrations and PPFD overall enhanced the macro nutrient use efficiency. Shade management, in increasing atmospheric concentrations of [CO2] appears to be a critical management strategy to maintain high sustainable cacao production in the tropical regions.