Research paperBiomass, spacing and planting design influence cut-and-chip harvesting in hybrid poplar

- Harvesting operations are among the largest single costs in SRWC production systems.
- Planting design affected poplar yield and harvester throughput by over 25%.
- Higher plant density affected poplar yield and harvester throughput by over 10%.
- The effect of planting design and spacing on fuel use may be minor at small scales.
- There may be risks delaying harvests where trees sizes approach machine capacity.

Hybrid poplar is a woody crop grown for the production of bioenergy, biofuels and bioproducts. Harvesting is often the largest single cost in the production system and the development and optimization of equipment is evolving. The objective of this study was to evaluate the performance of a single-pass, cut-and-chip harvesting operation in commercial plantings that included four cultivars, two spacing treatments, and two coppice planting designs (dedicated, and interplanted with sawtimber). Approximately 15 h of harvesting using a New Holland 9080 forage harvester equipped with a purpose-built coppice header was monitored over four days. Stand biomass ranged between 34 and 78 Mg ha−1of fresh biomass and effective material capacity (Cm) of the harvester ranged from 10 to 78 Mg h−1of fresh biomass excluding headland activities. Tree spacing had a significant effect on Cm but cultivar and planting design did not. The treatments did not have discernible effects on machine fuel consumption (mean 83 L h−1; ơ 16.4) or crop-specific fuel consumption for fresh biomass (mean 1.34 L Mg−1; ơ 0.31). Crop-specific fuel consumption was positively correlated with engine load, and negatively correlated with standing biomass; this result was statistically significant but negligible (<1%) in terms of liters of fuel used for each additional Mg ha−1 of stand biomass for engine loads ranging between 30% and 110%.