Field Crops Research 74 02002) 13±22 Bactris gasipaes agroecosystems for heart-of-palm production in Costa Rica: changes in biomass, nutrient and carbon pools with stand age and plant density A. Aresa,*, J. Bonicheb, E. Molinab, R.S. Yosta aDepartment of Tropical Plant and Soil Sciences, University of Hawaii at Manoa, 3190 Maile Way, Honolulu, HI 96822, USA bCentro de Investigaciones AgronoÂmicas JoseÂ, Universidad de Costa Rica, San JoseÂ, Costa Rica Received 25 May 2001; received in revised form 1 October 2001; accepted 27 October 2001 Abstract Perennial tree crops develop through growth phases that differ in the rate of biomass and carbon build-up, and in the relative contribution of various pools and ¯uxes to nutrient cycles and nutrient supply for plant growth. To de®ne these phases in peach palm 0Bactris gasipaes) agroecosystems for heart-of-palm production, we estimated biomass in stands up to 20 years of age in the humid tropical lowlands of Costa Rica. Dry biomass of foliage, petioles and stems were estimated using allometric equations which have been previously generated by applying nonlinear seemingly unrelated regression procedures to data from harvests of peach palm plants. Total aboveground biomass trajectories through time were ®tted by a three-parameter logistic function with total biomass stabilizing at about 6.3 Mg/ha. There were no differences in standing biomass between stands on Andisols and Ultisols. Trends in nutrient pools through time were similar to those for biomass. The order in size of nutrient pools was N 0up to approximately 120 kg=ha > K 0up to 90 kg=ha > Ca 0up to 45 kg=ha > Mg, S, P 0all up to 15±17 kg/ha). Peach palm plant bases and coarse roots are relatively large fractions of total plant biomass, and consequently of sequestered carbon and nutrients. The amount of carbon per unit area in plant tissue in peach palm agroecosystems in the Atlantic region of Costa Rica was about 8% of the carbon in forests of the same region. # 2002 Elsevier Science B.V. All rights reserved. Keywords: Peach palm; Biomass and nutrient budgets; Carbon sequestration 1. Introduction in the rate of aboveground and belowground biomass accumulation, and in the relative contribution of var- The prolonged growth span of perennial tree crops ious pools and ¯uxes to nutrient cycles. Biomass has fundamental implications for carbon and nutrient accretion relative to the standing biomass is usually storage, and for nutrient cycling in agroecosystems. maximum during a period between the initial growth Perennial tree crops have distinct phases which differ phase 0i.e. establishment) and that in which a relative equilibrium in stand biomass is reached 0Blackman, 1968). Among nutrient cycling processes, nutrient * Corresponding author. Present address: Dale Bumpers Small retranslocation becomes a more important component Farms Research Center, ARS/USDA, 6883 South State Highway of the cycle as the crop age increases 0Miller, 1984). 23, Booneville, AR 72927-9214, USA. Tel.: 1-501-675-3834; fax: 1-501-675-2940. Thus, the identi®cation of growth phases is important E-mail address: [email protected] 0A. Ares). for calculating nutrient and carbon budgets and, in 0378-4290/02/$ ± see front matter # 2002 Elsevier Science B.V. All rights reserved. PII: S 0378-4290001)00196-4 14 A. Ares et al. / Field Crops Research 74 52002) 13±22 developing diagnosis, prediction and economic ana- thesized that the onset and duration of growth phases lyses for integrated nutrient and crop management. The are modi®ed by stand density. On the other hand, we onset and duration of the growth phases in perennial anticipated that soil type would have a minor effect on tree crops are often not self-evident because they growth trajectories because soil nutrient status is depend upon species growth patterns and phenology, rather uniform as a result of fertilizer application, stand density and crop management. These growth and drought stress is unlikely in the Atlantic region phases have to be determined separately for almost of Costa Rica. every tree crop and apply to a given set of management Previous biomass estimates in peach palm stands conditions and geographical areas. were site-speci®c and provided only an indication of Peach palm 0Bactris gasipaes) for heart-of-palm trends in biomass accumulation because of the reduced has become an important perennial crop in the humid size of plant samples and stand ages. In Hawaii, above- tropics of Latin America 0Mora Urpõ et al., 1997; ground biomass at 1.3 years ranged between 0.45 and Deenik et al., 2000), where it is mostly grown on 1.40 kg of dry matter per plant 0roughly 2±7 Mg/ha) in Andisols, Oxisols and Ultisols in Costa Rica and peach palm experimental plots with a density equiva- Brazil. Peach palm is a caespitose, usually spiny palm lent to 5000 plants/ha 0Clement, 1995). In Costa Rica, that continuously produces new shoots that are pur- harvest of a few plants from a 3-year-old stand with posely controlled in number to optimize production. 3200 plants/ha, yielded 7.1 Mg/ha of standing dry Harvest for heart-of-palm begins at 1 or 1.5 years, and biomass 0Herrera, 1989). continues during the life of the stand which may Belowground biomass may account for an impor- surpass 20 years. Four growth stages have been tant proportion of total biomass in peach palm stands described for palms: embryonic, seedling, establish- especially as stand age progresses. Peach palm has ment, adult vegetative and adult reproductive 0Tom- shallow and coarse roots with 58±80% of the root linson, 1990). In peach palm stands for heart-of-palm, biomass found in the top 20 cm of the soil 0Ferreira the ®rst two of these phases take place in the nursery, et al., 1980, 1995; LoÂpez Morales and Sancho Vargas, and only the establishment and adult-vegetative 1990; Jongschaap, 1993), but total belowground phases occur in the ®eld. During the establishment biomass has not been estimated in the ®eld. The roots, phase which extends from planting to approximately the rhizome and a ®brous tissue below the base of the ®rst harvest, peach palm produces bi®d eophyll the stem form a clump which increases in size with and later pinnate leaves while the adult vegetative time. We, therefore, hypothesized that belowground phase starts at the beginning of stem elongation and biomass may surpass that of aboveground biomass in lasts until the ®rst ¯owering 0Clement, 1995), a pheno- mature stands. logical event that does not take place in heart-of-palm Because of the large annual biomass production, we production. For purposes of developing management also hypothesized that soil organic carbon may recommendations for fertilization and control of shoot increase with extended cropping. Plant residue pro- density, the growth stages in heart-of-palm production duction measured during 48 weeks in 4±5-year-old with this species can be divided into establishment, peach palm stands averaged 11.4 Mg/ha of dry bio- fast growth and maturity. In the context of this study, mass 0Molina, personal communication). The test of the term maturity refers to the stage in which a the hypothesis was not strictly rigorous in this study stabilized level of biomass is reached. The span because the initial soil organic carbon values were of these growth phases in peach palm stands of unknown. If effects on soil are strong, however, it may varying stand density and grown on different soil be possible to ®nd signi®cant differences with time. types in the Atlantic region of Costa Rica was On the other hand, continued fertilization is likely unknown. to decrease soil pH and exchangeable cations, and In recent years, stand density of peach palm in increase exchangeable acidity. In a fertilization experi- the Atlantic region of Costa Rica has been consisten- ment on a Typic Dystrandept in Costa Rica with tly increased from a traditional level of less than N:P:K applications up to 550:87:225 kg/ha per year, 4200 plants/ha 0spacings at 2.50±2:65 m  1m) to respectively, soil pH decreased from 5.5 to 4.5, 10 000 plants/ha 02 m  0:5 m), or more. We hypo- and exchangeable acidity increased from 0.30 to A. Ares et al. / Field Crops Research 74 52002) 13±22 15 1.21 meq/100 gwhile Ca, Mg and K decreased after 48 0Ares et al., 2001) generated by a non-linear regression months of heart-of-palm production 0GuzmaÂn, 1985). procedure 0Parresol, 1999) to calculate the above- The size of the carbon pools in peach palm stands is ground component and aboveground total plant bio- also important given the current interest in carbon mass as a function of shoot basal diameter. With this sequestration in the tropics. Some landowners in Costa regression method, plant component estimates add up Rica are already receiving compensation for preser- to the aboveground total plant biomass and also, ving forests, and research on the soil and plant carbon residuals are modeled to ensure equal error variances sequestering potential of agricultural systems in the through the range of the independent variable. Bio- region is underway 0Bulte et al., 2000). In terms of mass estimates from the equations were similar to data area, peach palm is the second most important per- from independent harvests 0Ares et al., 2001). ennial crop in the Atlantic region of Costa Rica after We tested the ®t of different regression models to banana comprising some 12 000 ha, while the total biomass data from low 0<4200 plants/ha) and high area of peach palm in Central and South America is density 0>4200 plants/ha) stands using the NLIN pro- about 24 000 ha 0Mora Urpõ et al., 1997).