Jeffrey W. Hoy

Mechanization of the harvest was a major turning point in the history of sugarcane production in Louisiana. Harvesters were developed that would cut whole stalks of sugarcane and drop them across rows on the ground to be picked up and placed in transport wagons. This system was used for many years.

Within the last five years, however, another major change has occurred in the sugarcane harvesting system used in Louisiana. Sugarcane is now harvested with what are known as “chopper” or “combine” harvesters that cut cane stalks into sections or “billets” as they pass through the machine. The billets are carried up an elevator and then dropped into a wagon traveling alongside.

This type of harvesting system offers several advantages. Sugarcane can be cut without burning, and it never touches the ground. Burning and contact with the ground both can accelerate deterioration and sugar losses in cane stalks. In addition, and of even greater significance to farmers, this type of harvester can more effectively pick up sugarcane that has “lodged” or fallen down. This then makes it possible to grow high tonnage sugarcane varieties that typically lodge by the end of the season. Because the old, whole-stalk harvesters could not handle high tonnage, lodged cane, varieties of this type could not be developed by the sugarcane breeding program. As mentioned in other articles in this issue, the ability to grow new, heavy tonnage varieties is increasing the yields obtained by Louisiana sugarcane farmers and keeping them in business.

Climate Affects Planting Method
Combine harvesters have been used in most other places around the world for many years, but they were evaluated several times in the past in Louisiana and deemed a failure. The problem was the climate. Sugarcane is grown at the northern limit of its cultivation range in Louisiana, so the growing season is short. The crop must be harvested before a killing freeze occurs. As a result, the harvest must take place during a short period of time and must proceed even in wet weather.

Because early versions of combine harvesters bogged down in the muddy fields, the Louisiana industry kept using whole stalk harvesters. In addition, whole stalks were needed for planting to help control a disease called stalk rot (Figure 1) that rots planted sugarcane and can severely reduce spring shoot populations and yield. Stalks of sugarcane are planted in the late summer, and bud germination and shoot elongation begin in the fall. The occurrence of frosts and freezes during winter then kills the above-ground growth, and the planted stalks and young shoots must sit in the cold, wet ground for several months. Severe stalk rot can result in a stand failure and necessitate replanting.

The failure to establish a plantcane (first year) crop is the worst loss a farmer can sustain. When the previous crop is plowed out, the land does not produce a crop during that season. Then, the stalks used for planting represent a loss, since that cane would have been harvested and sent to the mill for sugar extraction. With whole stalks, it is less likely that the rot will progress through the entire stalk than with the shorter billets. In addition, a higher planting rate (more stalks planted) is used than in other regions of the world to be able to sustain losses to stalk rot and still be able to establish an adequate spring shoot population. This expensive planting system was adopted to ensure that adequate plant cane stands are established each year.

Billets are planted in other places around the world, but planting billets also has been evaluated in the past in Louisiana and deemed to be too risky because of the greater potential for stand failures. Yet, with the increasing use of combine harvesters, there has been intense, renewed interest within the industry in finding methods that would allow successful billet planting. It is expensive to maintain two harvesting systems just to be able to cut whole stalks for planting. In addition, there are advantages associated with billet planting. Labor requirements are reduced with mechanical planting, and the current mechanical planters plant billets more effectively than whole stalks. Planting billets goes rapidly, and the amount of time and labor required for planting is reduced.

Switching to Billets
Considering the failures of the past, is there any reason to think that billet planting would be more successful this time? One difference is in the varieties being grown. Many of the new sugarcane varieties have come from what is known as basic breeding, in which agronomically desirable sugarcane varieties are crossed to wild relatives with plants consisting of large numbers of grassy, small-diameter shoots. The basic breeding program has been conducted by the USDA Sugarcane Research Unit in Houma, La., for more than 30 years. The material generated by this program is used in the Louisiana Sugarcane Breeding Program, which is a cooperative effort among the LSU AgCenter, USDA’s Agricultural Research Service and the American Sugar Cane League. The higher shoot populations and increased vigor of some of the new varieties could affect billet planting performance. In addition, new fungicides and other types of biological and chemical treatments are available that might reduce stalk rot severity.

A research project evaluating factors affecting billet planting has been conducted cooperatively by the LSU AgCenter, the American Sugar Cane League and sugarcane farmers for the last six years. The early field experiments demonstrated that varieties vary in tolerance of billet planting, and this offers some hope for breeding and selecting for varieties that can be successfully planted as billets. Unfortunately, no chemical or biological treatment has been identified that will control stalk rot and improve billet planting performance. Instead, a series of cultural practices that indirectly reduce disease severity and promote vigorous plant growth has been identified that will maximize the chances of success in billet planting.

Planting Billets
Billets are more sensitive than whole stalks to stress conditions. This is because stalk rot severity is increased by stressful conditions such as drought or water-logging. As a result, good planting practices are essential for billets. These include proper soil preparation and depth of cover, establishment of good drainage and careful weed control. Adding fertilizer at planting has been beneficial in most experiments and continues to be evaluated.

Other important factors affecting billet planting performance are related to the type and amount of billets used for planting. Normal billets cut during harvest for the mill are about 10 inches long. The harvester must be modified to cut billets 20-24 inches for planting. In addition, it is important to minimize physical damage to the billets, because the pathogens that cause stalk rot gain entry to the internal stalk tissues through wounds. Planting a longer billet with minimal damage will reduce the severity of stalk rot. Research is identifying harvester modifications that will reduce damage and produce the highest quality billet possible.

Finally, the rate of planting affects billet planting (Figure 2). Cutting and planting more seedcane is expensive, but higher rates of planting are needed with billet planting. Billet plantings must be able to sustain stalk rot damage and still produce an adequate stand.

The research results have shown that whole-stalk planting will produce the maximum yield over multiple crops and years with the least risk. Thus, it will continue to be a recommended practice. However, severe stand problems have not been encountered with billet planting when using the practices described above. In addition, the new high-yielding variety, LCP 85-384, has shown some tolerance of billet planting. As a result, billet planting will now be recommended as an alternative to whole-stalk planting. Billet planting may offer some advantages over whole-stalk planting that would be attractive to some farmers, but perhaps the greatest factor leading to a recommendation for billet planting is that severe lodging before the planting season is common with high tonnage varieties, such as LCP 85-384. Whole-stalk harvesters cause extensive damage to badly lodged cane, so the best option in this case will be to cut and plant billets.

Farmers would prefer to plant billets, but many keep a whole-stalk harvester in working condition to cut seedcane if the stalks are standing. Caution is still in order. However, if methods for successful billet planting are proven, the Louisiana sugarcane industry will rapidly switch to billet planting. Planting billets under Louisiana growing conditions is a challenge. The LSU AgCenter conducts research to meet that challenge.

Jeffrey W. Hoy, Professor, Department of Plant Pathology & Crop Physiology, LSU AgCenter, Baton Rouge, La.

(This article was published in the fall 2001 edition of Louisiana Agriculture.)