Long term effects of machine harvesting on yield
Long term effects of mechanical harvesting on yield are being investigated in a long term yield trial. Initial data indicates that machine-harvesting does depress yield, especially if an excessive number of harvester passes with vigorous shaker settings are used. By using techniques such as layer harvesting, the number of passes imposed on any section of a tree is two. This reduces the potential for long term damage.
Economics
As with all mechanical harvesting, the labour saving of mechanisation must be traded against the lower crop recovery. The analysis in Table 1 is based on recovery data from a series of trials, giving actual comparisons of the recoveries of cherry from a number of harvesting and hand-picking regimes, including a hybrid strategy, where hand-picking is conducted two or three times, and the bulk of the crop is removed in one machine pass. A final hand-pick can then be used to recover the final crop. This technique has been used for harvesting trials in North Queensland and has been used commercially in northern New South Wales.
Although actual hours were not recorded, the labour costs of hand-picking were calculated at the very high work rates of approximately 150 kg/ eight hour day when selective picking early in the season, and 200 kg/day late in the season when little immature cherry is present and strip-picking can be used. It is also assumed that harvest aids such as picking rings and hessian ground sheets are used to help achieve these picking rates. No data for hand-held pneumatic harvesters are included in TABLE 1 as this equipment was not available.
Machine-harvest rates were based on those actually used in the trials. For selective harvesting passes, work rates of 0.6 to 0.8 km/h were used, whereas for one pass/final pass operations, operating speeds of 1.0 to 1.2 km/h were used. The harvester cost was calculated at $120.00/h.
The economic data presented shows that hand-picking can only compete with machine-harvesting at high product prices and where harvester recovery is poor. Even when hand-picking is used in conjunction with machine-harvesting, it reduces profitability.
TABLE 1 Harvesting costs and recovery of coffee under different harvesting regimes. Please refer also to the information below.
Picking regime*
This column indicates the type and number of harvesting passes made.
Labour productivity assumptions for hand picking:
- Initial 25% of crop harvested at 50 kg/8 hour day (very selective picking, predominantly immature cherry on bush)
- Subsequent 35% of crop harvested at 100 kg/8 hour day (selective picking, greater proportion of mature cherry)
- Remaining 40% of crop harvested at 150 kg/8 hour day (little immature cherry - strip-picking techniques used)
Coffee being handpicked
- Labour costs of $12 hour are used
Recovery (based on trial results):
- Immature: 5.5 kg cherry gives I kg green bean - no commercial value
- Prime: 6.5 kg cherry gives I kg green bean - valued at $3, $6, $9 and $ 12/kg green bean, representing the range of prices achieved by growers
- Mbuni: approx. 3 kg cherry gives I kg green bean - valued at 50% of the selected value of prime green beans
Source
Chris Norris
