Macro and Micro Nutrient Uptake Parameters and Use Efficiency in Cacao Genotypes as Influenced by Levels of Soil Applied K

Aims: To evaluate the effects of soil K levels (deficit to excess) on nutrient uptake parameters (concentration, uptake, influx, transport and use efficiency ratios) of macro and micro nutrients in different cacao (Theobroma cacao L.) genotypes.
Methodology: Seedlings of three cacao genotypes (Amelonado, EET-400 and ICS 95) were grown for 90 days in a plant growth chamber with three levels of K (52, 156, and 469 mg K plant-1) in the growth medium. The experiment was a split plot design with genotypes as the main plots and K levels as the subplots with three replications. Nutrient uptake parameters were investigated.
Results: Significant (P<0.01 and 0.05) K effects were observed on the nutrient uptake parameters of various macro and micro nutrients in cacao. Increasing K in the soil significantly increased K (P<0.01) and Zn (P<0.05) concentrations and significantly (P<0.01) reduced the P, Ca, Mg, and Mn concentrations in cacao plants. Overall uptake of P, Ca, Mg, Fe, and Mn decreased and uptake of N, K, Cu and Zn increased with increasing soil K levels. Increasing the K levels of the soil significantly at P<0.01 and P<0.05 increased the efficiency ratio (ER) for P, Ca, Mg, Mn and N respectively in cacao. Increasing K levels of the soil significantly (P<0.01 and 0.05) decreased ER for K and Zn respectively in cacao. For all of the soil K levels, Amelonado genotype was most efficient in utilization of absorbed Fe, Mn and Zn, whereas ICS 95 genotype was most efficient in utilization of absorbed N, P, Ca, Mg, B, and Cu.
Conclusion: At varying soil K levels, cacao genotypes used in this study showed significant differences in macro and micro nutrient uptake, nutrient influx and transport and nutrient use efficiency. Soil K levels have significant effects on nutrient uptake parameters of cacao.