Developments in Handling Sugar Beets

Myron Stout, S. W. McBirney, Charles A. Fort.

Recent developments in harvesting, storing, and processing sugar beets have greatly increased the efficiency of domestic production of sugar, our largest single item of imported food.

Mechanical harvesting is finally replacing hand methods, which have remained much the same ever since the industry was introduced into the United States about 80 years ago. Even the change from horses to tractors for harvesting and from the horse-drawn wagons to motor trucks for hauling did not greatly alter hand topping and loading methods. Before 1943 (when about 135 harvesters were built and used), not more than 15 or 20 machines were in commercial use, and they were experimental. The first machines for loading windrows of hand-topped sugar beets, many of them made by small manufacturers and local shops, elevated beets from a windrow into a truck driven alongside the loader. Their use for hand-topped beets may be a passing phase. To meet the need for more complete elimination of hand labor, sugar-beet harvesters are used. Some commercial harvesters leave the beets windrowed in the field, and for them windrow loaders will still be necessary. But equipment is favored that puts beets directly into trucks or trailers, rather than windrows.

From 1943 until 1948 the number of machines built each year was roughly double the number built the preceding year. The percentage of the crop mechanically harvested also was roughly twice that of the previous year until 1948, when about half the acreage was harvested mechanically. In 1949, when 54 percent was machine-harvested, the further increase was small, partly because of bad harvest conditions in some sections. In 1949 about 1,900 harvesters were sold and 9,100 were in use. Most of the larger growers now have harvesters.

Mechanization of the harvest has been more rapid in California than in other sections, because of the development of a harvester particularly suited to conditions there large-scale operations, favorable weather during harvest, and a longer harvest season. In 1949, about 73 percent of the sugar-beet acreage in California was machine-harvested; more than 60 percent in Idaho, Washington, Oregon, and Utah; nearly 49 percent in the eastern slope of the Rocky Mountain area, including irrigated areas of Kansas, Texas, Nebraska, and the Dakotas; nearly 40 percent in the Minnesota-Iowa area; and about 35 percent in Michigan-Ohio.

Most of the harvesters in use today do a complete job. They dig the beets and put them, topped and ready for storage or processing, into trucks or trailers in one pass through the field. Some machines drop the beets in windrows, which are loaded with a separate machine. One type tops the beets in the ground, then digs them and separates out the soil. Another type digs the beets first and tops them in the machine. Some machines are tractor-mounted; others are pulled. Most are 1-row machines, but 2-row machines are more common on California's large fields. The harvesters travel 2 1/4 to 3 1/2 miles an hour or more. The 1 -row machines harvest 2 1/2 to 3 or more acres a day and usually average 50 to 75 acres a season. Some harvest more than 100 acres. The 2-row machines harvest about 5 acres a day and, with the long harvest season in California, average about 250 acres a season. Some harvest more than 500 acres.

A new development in mechanical harvesting came into use in 1947 in Idaho. It is the beater-topper, which beats off, chops up, and scatters the stems and leaves of the beets. It has one or two beater shafts, which carry rubber flails. The beater is mounted under a hood, crosswise to the beet rows, and is driven at 600 to 800 revolutions a minute, either by a power take-off from the tractor or by an auxiliary engine. It is necessary to cut a thin slice of crown from the beets to improve storing and processing properties. Equipment to do that has-been developed. The beater-topped beets are usually dug by multiple-row diggers, which lift the beets and soil to a bed of kicker rolls. The rolls remove the loose soil before the beets are elevated to a truck or trailer. The machine is best suited for friable soils, where no clods or wet lumps of soil come up with the beets. A disadvantage is that the tops and crowns are lost for stock feed.

Mechanization of the beet harvest has brought large savings in labor requirements and costs. The savings over hand harvest depend on the yield, the previous methods of hand harvest, the machine, the depreciation period, seasonal use of the machine, and the size and efficiency of operations. The savings in both man labor and cost increase rapidly as yields increase. And, as with all machinery, more days of use during the season spread the overhead cost over more acres, reducing the cost of harvest per acre. Average harvest-labor requirements have been 30 to 35 man-hours an acre for hand harvest; they average 6 to 7 hours for machine harvest. The saving by mechanization usually ranges from 20 to 30 Man-hours an acre. The cost saving by Mechanizing the harvest, taking all Costs into consideration, probably averages about 15 dollars an acre. As more than half of the 900,000-acre crop in the United States in 1950 was harvested by machine, the saving to beet growers was more than 7 million dollars.

Sugar beets are grown principally in temperate climates, where the growing season may be from 5 to 8 months. The longer growing seasons generally produce higher yields. The harvest has to be finished before wet weather makes the work difficult or freezing weather damages the crop. The extractable sugar per acre sometimes increases more than 25 percent during the last month of a short growing season, but the late increase is usually less in areas with longer growing seasons. Economic crop production, therefore, requires that maximum advantage be taken of the growing season and that the beets be harvested when high yield and quality are attained.

The fixed costs of factories for processing sugar beets are necessarily high. Estimates based on 1948-49 costs are that a factory capable of processing 2.800 tons of beets a day will cost about 7 million dollars and will require approximately 150 thousand dollars a year for maintenance. Obviously, only a large yearly volume can insure profitable operation, and the operating period of a factory must be extended far beyond the ideal harvest season that would give maximum economy of crop production. Between the opposing economic factors of reduced yield and quality by prolonged harvest and high-cost of factory capacity for direct processing lies the possibility of storing the crop harvested at the best time until it can be processed by a factory that can operate long enough to make its expenses and some profit.

THE BREEDING OF IMPROVED varieties of biennial sugar beets has produced a superior type for storage. Roots have been stored from one season until the next in order to produce seed the second year. The roots that did not store well were eliminated from seed production. Losses of sugar do occur in beets that are stored, however. We therefore have three economic factors to consider cost of crop production, factory capacity, and storage losses.

About 3 million tons of beets are stored each year from 3 weeks to 3 months. An equal amount is stored from 1 to 3 weeks before processing. Normal storage amounts to from 120 million to more than 200 million ton-days. Normal losses range from about 0.2 pound to more than 1 pound of sugar a ton a day of storage. Rapid spoilage frequently develops in storage piles. Sometimes losses amount to as much as 5 pounds a ton a day, or to complete loss in a few weeks if the beets are not quickly processed. Removal of the hazards of storage is the primary problem of commercial-storage improvement.

Storage losses result from two general causes: Through the normal process of respiration of the living tissues of the beet, whereby oxygen is absorbed, stored food, principally sugar, is used up, and carbon dioxide, water, and energy as heat are given off ; by spoil-Age through the action of invading organisms, principally certain species of fungi.

Both factors must be considered in attempts to improve commercial storage, because some conditions may reduce loss from one cause and increase loss from the other. Many factors influence losses from respiration and spoilage. Several investigators have agreed that each increase of 15 to 18 F. doubles the rate of respiration, but they have failed to agree on the respiration rate at a given temperature, indicating that other factors also caused large differences.

Studies of some of the other factors showed that partly dried or wilted beets respired and also spoiled more rapidly than fresh, crisp beets. Beets that were topped high respired more rapidly, but were less subject to spoilage than low-topped beets. High-topped beets also yielded more sugar to the acre. Lowered oxygen concentration in the storage atmosphere reduced respiration, but increased spoilage, especially if the oxygen concentration was below 5 percent. Increased carbon dioxide concentration (up to 5 percent studied) reduced both respiration and spoilage.

Beets grown in a cool climate respired much more rapidly at a given temperature than those grown in a warmer climate. Broken beets and beets severed into top and bottom halves and stored together respired and spoiled more rapidly than whole beets. The top halves of severed beets, when stored separately, respired more rapidly, but the bottom halves were more subject to spoilage.

Healthy beets stand relatively rough treatment in harvesting, handling, and piling without an appreciable increase in respiration or spoilage. Treatment of beets with disinfectants or fungicides has had little effect on respiration and usually has increased spoilage. Treatment with methyl ester of naphthaleneacetic acid, which is used to prevent sprouting of potatoes, nearly doubled the respiration rate and increased the inversion of sucrose. The chemical apparently reduced top growth, but increased the development of small rootlets on the beets.

One variety of beets respired and also spoiled more rapidly than another variety grown and tested under the same conditions. Breeding improved varieties for storage, therefore, appears promising. Beets that were deficient in phosphorus spoiled more rapidly than those given enough. Boron-deficient beets developed heart rot in the growing crop even before storage and continued to spoil during storage. Unbalanced nutrition, therefore, may be expected to affect storage adversely. Research has indicated that any treatment that seriously interferes with the normal functioning of the living tissues of the beets adversely affects storage and that healthy beets have a strong resistance to invasion by most fungi.

Losses are the lowest when healthy, freshly harvested, clean beets are immediately stored at the lowest temperature possible without freezing, in a storage environment that produces little drying and no persistent moisture on their surfaces and is ventilated only enough to control temperature, eliminate respiratory moisture, and maintain adequate amounts of oxygen in the atmosphere. Low temperature seems to be the most important single factor in keeping losses down.