SPACE-TIME DEPENDENCE OF JATROPHA GROWTH PARAMETERS GROWN IN BRAZILIAN SEMIARID

ABSTRACT: Jatropha has emerged as a source of power generation in the semiarid region of Brazil. The objective of this study was to evaluate, using geostatistics, the spatial variability of stem diameter, plant height and seed weight of jatropha (Jatropha curcas L.) grown under rain fed conditions in Serra Talhada, Pernambuco state, Brazil. At 545, 905 and 1265 days after sowing (DAS), the stem diameter and plant height of 340 plants were measured with a digital caliper and a tape measure. At 545 DAS, the fruits of 306 plants were collected, the seeds extracted and their weights measured with a precision balance. For each date analyzed, the spatial dependence of the plant characteristics was evaluated from the adjustment of the experimental semivariogram. The spherical model was adjusted for modeling the spatial distribution of cultural parameters. The range of plant height reduced by an average of 37% from 545 DAS when compared to 905 and 1265 DAS, while for the stem diameter this parameter remained practically constant. Geostatistics can be employed to assist in future sampling and to identify areas with different patterns that can occur in the jatropha planting.摘要：麻疯树（Jatropha curcas L.）已成为巴西半干旱地区的能源作物来源。本研究借助地质统计学（geostatistics），旨在评估巴西伯南布哥州塞拉塔尔哈达地区雨养条件下种植的麻疯树的茎直径、株高与种子重量的空间变异性。分别于播种后天数（DAS）545、905及1265天时，使用数显卡尺与卷尺测定340株麻疯树的茎直径与株高；于DAS 545天时采集306株麻疯树的果实，脱粒后通过精密天平测定种子重量。针对各测定时期，通过拟合实验半方差函数（semivariogram）评估植株性状的空间相关性。最终采用球状模型对栽培性状的空间分布进行建模。相较于DAS 905与1265天，DAS 545天时的株高变程平均降低37%，而茎直径的变程基本保持稳定。地质统计学可辅助开展后续采样工作，并识别麻疯树种植园中可能出现的不同性状分布区域。