HARVEST GUIDELINES FOR SUGARBEETS

BURNING SUGAR

When harvest begins and sugarbeets are delivered to the receiving stations, they are stock piled and stored for periods of up to 150 days awaiting processing. During this storage period, sugar contained in the roots is used by the beets as an energy source for respiration. Respiration is a necessary metabolic function occurring in each root enabling the roots to remain alive and normally accounts for about 70% to 80% of sugar loss during storage. Once beets die, rot and decay start immediately and complete degradation of the roots takes place. Therefore THE GOAL OF SUCCESSFUL SUGARBEET STORAGE IS TO KEEP THE BEETS ALIVE, HEALTHY AND FRESH THROUGHOUT THE STORAGE PERIOD, WHILE AT THE SAME TIME HOLDING RESPIRATION AND ACCOMPANYING SUGAR LOSS TO A MINIMUM.

HEAT-THE SILENT ENEMY

Controlling root temperature during storage is the key to minimizing losses in storage due to respiration. When the temperature of stored roots remains low then respiration is minimized, but, when stored root temperatures increase, losses due to respiration increase also. Thirty-two degrees Fahrenheit is nearly ideal for maintaining limited metabolic activity in sugarbeet roots. Research has demonstrated that respiration rate, sugar loss, and heat output (which is a respiration by-product) double with each 15^o F increase in root temperature. Clean, well topped beets store better because they store cooler. Weeds, trash, tops, and dirt in a beet pile (Fig. 1, 2, 3) all inhibit air movement and usually result in the formation of hot spots. As root temperature rises, respiration increases. As respiration increases, more heat is emitted from the beet. Once begun, this destructive cycle becomes self-generating, and unless such hot spots are dug out and removed, they quickly spread and can be the cause of much sugar loss and beet degradation (Fig. 4, 5, 6). Because of the above mentioned storage considerations, the Grower agreement states in Paragraph 4 "...All beets delivered hereunder shall be free from excess dirt, rocks, trash, and foreign substances likely to interfere with work at the factory.. .The Grower shall protect the beets from sun and frost after removal from the ground..." It further states, "The LLC, at its option, may REJECT ANY DISEASED, FROZEN, DAMAGED, OR IMPROPERLY TOPPED BEETS, as well as beets not suitable for the manufacture of sugar...

DIRT-A COSTLY TWO EDGED SWORD

Dirt is not only a major factor contributing to reduced air movement, heat buildup and sugar loss in piles, but it is also a costly item for growers to handle. Factory District data, across all receiving stations, combining the years 1993, 1994, and 1995 shows a three year average of 968 pounds of dirt on every truck load of beets coming in to be unloaded. The cost to the grower of hauling, handling and disposing of this dirt amounted to $5.00 per incoming truck, or $.42 per ton of beets. Additionally, it is estimated that 240,000 tons of dirt enter the factories each year as the beets are processed. To remove and dispose of this dirt adds an estimated $420,000 to processing costs. A two year study by North Dakota State and University of Minnesota researchers evaluating sugarbeet harvesters (six row WIC, Artsway, and Parma machines were compared) showed no difference due to machine. But, when averaging across all machines, "percent tare dirt increases as harvester ground speed increased," and yield in tons--recoverable sugar per acre and gross income per acre decreased as harvest speed increased." The harvester speeds used were 4 and 6 mph one year and 3 and 5 mph the other. Yield differences due to increasing speed were attributed to increased tail breakage and more difficulty staying on the row and dirt differences were due to more soil moved into the machines and less cleaning time available. By far the most cost effective way for sugarbeet growers to handle dirt is to do everything possible to leave it in the field. Maintaining reasonable harvest speeds will contribute substantially to this effort.

PROPER DEFOLIATION

Scalping too deep on the roots (the Grower agreement states that "...distinctive evidence of leaf scar shall be left on each root after topping...") can accelerate losses by causing increased respiration and exposing more of the internal pith tissue to decay. Proper defoliation and scalping should remove all foliage and the upper crown growth point from the beets while at the same time avoiding excessive wounding of the upper root area. Well maintained equipment traveling at correct (not excessive) ground speed, with proper flail arrangement and scalper adjustment are necessary for proper defoliation. Beating and scalping too far ahead is detrimental to beet storage quality all harvest long. In the early portion of harvest the leaves shade the roots, thus maintaining cooler root temperatures for delivery to the storage pile. Later in harvest, as the weather gets colder, the leaf canopy provides protection from the roots being frosted or frozen prior to digging. Beating ahead only those beets that will be harvested each day, will enhance beet storage conditions for the entire storage period (Fig.7). FROST One of the great threats to successful storage is stock piling roots that are frozen or frost damaged. During periods of potential frost, care should be taken to see that all defoliated and scalped beets are harvested each day. When frost has penetrated the roots, these partially damaged beets will recover better and therefore store better if they are allowed to thaw in the field before being harvested. Loaded trucks held overnight should be kept under cover in storage sheds to prevent freezing of the surface beets. Loads containing frozen beets (Fig. 8) will be rejected at the receiving station. Once frozen beets are in a pile, the heat generated from respiration is adequate to cause thawing, thus allowing frost ruptured cells to begin leaking juice throughout the pile and becoming an instant site for rot and decay. Frozen beets can, within a few short days, literally cause a beet pile to begin to melt (Fig.9).

PILE PROTECTION

Temperature tubes to monitor pile temperatures are placed in all piles at harvest time along with date of delivery stakes to correlate location in the pile with weather conditions at time of delivery. This is done in an effort to help identify any suspect or trouble areas that might occur with time in storage. In addition, aerial thermoscanning is utilized periodically throughout the storage season to look for trouble spots developing in the piles. Once identified, spots which are starting to heat up and get bad are removed and processed as soon as possible to keep losses from such spots at a minimum and to protect the integrity of neighboring beets in the pile.

THE IMPACT OF STORAGE

Since sugar cannot be extracted and recovered from sugarbeets until they are processed, good or bad storage conditions will always have a major impact on the overall profitability of the Cooperative. Thus it is in the best interest of everyone to stockpile and store only clean, properly topped, disease and frost free beets that will maintain their stored sugar and physical integrity until processed.

Return to the Agronomy Page