Biomass and nutrient accumulation from heart-of-palm production in mature peach palm plantations of Guápiles, Costa Rica

Abstract

Harvested offshoots for commercial heart-of-palm and pruned excess offshoots were measured at 4-week intervals across 52 consecutive weeks in 4 and 8 year stands at Guápiles, Costa Rica in order to characterize annual accumulations of above- ground biomass, N, P, K, Ca and Mg that are harvested, exported, and recycled in mature plantations of peach palm (Bactris gasipaes Kunth) managed for heart-of-palm production. Measurements in each peach palm stand were taken in six 20 m² plots. The standing biomass of developing offshoots in equilibrium with the commercially harvested offshoots was estimated by destructively sampling all plants after the final offshoot harvest at 52 weeks. Despite seasonal differences in the number of offshoots that were either harvested or pruned to maintain a constant population of developing stems, both stands had similar cumulative numbers of harvested offshoots and biomass across the 12 months as well as developing offshoot biomass. Based on averages across both stands, 13.1 t ha^-1 of offshoot dry matter was harvested during the year with only 11% removed from the field as 11214 hearts-of- palm and protective stem sheaths. Dry matter for the cumulative annual harvests exceeded that of the standing vegetation of developing offshoots by a factor of 1.9 in the 4 year stand and 2.7 in the 8 year stand. The proportion of nutrients in the standing biomass of developing offshoots, relative to that for all offshoots harvested during the 12 month period, ranged from 36% for Ca to 55% for P. Foliage (leaflets, rachis and petioles) comprised 73% of the 11.5 t ha^-1 of residues left in the field as mulch during the year. A linear relation between offshoot dry matter and the number of heart-of- palm for individual harvests in both stands provided an estimate of 1.04 kg of offshoot dry matter for each commercial heart-of-palm. Likewise, linear relations between dry matter and the combined nutrient uptake of harvested offshoot components predicted mean nutrient concentrations in the harvested offshoots of 1.40% N, 0.27% P; 1.60% K; 0.37% Ca and 0.21% Mg.