Influence of chopping length on capacities, labour time requirement and costs in the harvest and ensiling chain of maize

Increased methane yields and enhanced ensilability are reasons in favour of very short cutting lengths when chopping crops for biogas utilisation, though this also leads to higher expenditure at harvest. The objective of this study was to evaluate the effects of very short chopping lengths in maize harvesting on capacities, labour time requirements and process costs of the harvest and ensiling chain. Based on data gathered in field experiments, a model calculation that allowed linkage of harvest and transport processes was applied to assess capacities and machinery performance. Results show a decrease in overall area capacities of harvest and transportation units by 4–24% at a nominal chopping length of 4–6 mm compared with common chopping lengths of 8–10 mm. Harvesting costs increased by 4–21%. The effect of lowering machinery chain performance was diminished with more powerful forage harvesters, smaller field sizes, and larger transport distances. Hence, considerable additional expenditures are to be assumed with shortening of chopping length. However, effects depend on particular field and machinery conditions. There is further need to take the additional benefit for storage and methane production into account before recommendations for optimal length of cut can be provided.