Biomass yield stability of interspecific Jatropha hybrids through multiple harvest rotations with varying harvest ages

Abstract

Importance of the work: The consistency of biomass production is crucial for Jatropha cultivation as a short rotation woody crop for use as a biomass source.
Objectives: To investigate the effect of harvest age on Jatropha hybrid growth, assess the relationship between growth traits and biomass yield and evaluate the biomass yield stability of interspecific hybrids between Jatropha curcas and J. integerrima.
Materials & Methods: For 5 yr, 14 genotypes of Jatropha hybrids, were evaluated in the field, using three different harvest age rotations. Plant height, canopy width, stem and branch diameter and biomass yield were measured.
Results: Harvest ages and genotypes affected Jatropha hybrid growth traits. Jatropha hybrids grew larger with age. Plant height, canopy width and stem and branch diameter were all highly correlated with biomass yield (correlation coefficient range = 0.59
[p < 0.05] to 0.94 [p < 0.01]). At the first, second, third, fourth and fifth harvests at 12 mth intervals, the Jatropha hybrids had average biomass yields of 45.91 t/ha, 40.63 t/ha, 36.46 t/ha, 42.77 t/ha and 37.29 t/ha, respectively. Although harvest frequency affected biomass yield, the yield did not substantially decrease, suggesting pruning tolerance of the Jatropha hybrids. The optimal harvest age rotations for Jatropha hybrids were intervals of 12 mth and 18 mth, due to the highest five-yearly total biomass yields of 202.79 t/ha and 221.29 t/ha, respectively. Furthermore, the KUBJL 14 genotype had the highest growth and biomass production.
Main finding: The growth traits of the Jatropha hybrids could be used to assess biomass production. Jatropha hybrids have a high biomass potential and good biomass yield stability, even after multiple harvests.