Effect of pruning history on growth and dry mass partitioning of jatropha on a plantation site in Madagascar

While technical aspects of oil processing of seeds of jatropha are under intensive investigation, comparably little is known about the performance of jatropha in the field. We investigated the effects of water availability (rainfed versus irrigated) and pruning-induced differences in plant stature on growth, biomass partitioning, and canopy size at a plantation site in Madagascar in 2010. Plants of different pruning types differed in trunk height (43 versus 29 cm) and primary branches total length (171 versus 310 cm). The two pruning types had effects on dry mass formation and leaf area projection (LAP) during the vegetation period. Trees which had a shorter trunk and longer lateral branches produced more biomass and had a higher LAP. Total dry mass formation varied from 489 to 912 g m⁻² and LAP from 3.26 to 7.37. Total aboveground biomass increased from 2.3 ± 0.5 to 4.89 ± 1.4 kg tree⁻¹ and from 4.6 ± 1.8 to 8.9 ± 1.0 kg tree⁻¹ for the pruning types with shorter and longer lateral branches, respectively. Growth of twigs and leaves was positively correlated with total length of branches. Relative dry mass allocation to branches, twigs and leaves, length of twigs per cm of branches and specific leaf area (13.57 ± 0.72 m² kg⁻¹) were not affected by pruning and water supply. Trees with shorter branches had higher LAD. Results indicate that pruning type should be considered as a management tool to optimize biomass production. Detailed studies on effects of canopy size and shape on radiation interception and growth are required to improve the productivity of jatropha.