Combine Studies - 72



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Project Leader and Principal UC Investigators

S.M. Henderson, W.J. Chancellor, J.R. Goss, Crop Residue Management - Field Hulling of Paddy Rice (70-24)

W.J. Chancellor, Rice Production, Processing and Marketing Systems Analysis and Optimization (70-16)

V. Cervinka

W.R. Grant

S.S. Johnson

D.E. Seaman



Hull disposal would be solved if rice were hulled in the combine as a step in harvest. Lab tests have shown that a rubber-roll huller hulled rice of 25% moisture as well as the job done by in-mill hulling of dry rice - about 80% effectiveness. Steel-roll hulling was 45-50% effective under the same conditions.

Despite the success of the rubber-roll hulling, its adoption is inadvisable because of certain complications: the hulled wet rice checks about four times as badly as rough rice dried under the same conditions; free fatty acids increase faster in stored dried brown rice than in rough rice; and hulling equipment on a combine would be heavy, use considerable power, and require a uniform flow of clean rough rice.

Such problems could probably be solved: Stage drying at lower temperatures would provide an acceptable head yield. The brown rice could be heat-treated to inactivate enzymes or held in cold storage or (probably) in controlled atmospheres that slowed the formation of free fatty acids (70-24)


When a grower's acreage is a single variety all maturing at once in a period of hot dry winds, a three-day harvest is the time limit for avoiding losses in crop value. Each additional day will see a loss of crop value of about $1.50 per acre for that variety. Minimizing total harvest costs will then require high threshing rates and about one combine for each 120 acres of that single variety. In one area a study revealed that the resulting total harvest cost of $75 per acre is $5 per acre less than with the current practice of 80 acres of one variety per combine.

Further large economies are possible, however: In an area served by a single rice dryer, rice of one variety can be found coming to maturity over a fairly broad range of dates. If, then, combine capacity in the area were concentrated on the acres just ready for harvest, losses in crop value for each day beyond the optimum 3-day period could be limited to 37 cents per acre (vs $1.50). Additionally, harvest costs (including all losses) could be minimized at $60 per acre (vs $75 or $80) by operating the combines at speeds only slightly above normal and having each combine serve about 240 acres during each varietal season.

Those examples represent extremes but illustrate the definite potential for lower harvest costs. Thus, combine capacity in an area can be matched with harvest demand by modern management techniques such as machinery pools, custom work, work exchange, and cooperative ownership.

The fact is that fixed costs of harvesting equipment are so high that they must be spread over as many acres as possible. The large economies stemming from increased use of each machine will far outweigh the moderate increases in other costs associated with such greater use: reduced timeliness, possible weather losses, and extra labor and repair expenses. (70-16)


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