Progress With Sugar Sorgo

by E. W. BRANDES

SORGO IS grown extensively for table sirup. If it could be made to yield better, it might be used to make sugar. Sorgo is the name of convenience applied to the juiciest, sweetest-stemmed variants found in many species of the genus Sorghum. Between sorgo and grain sorghum, which commonly has dry, pithy stems, there are many intermediate types with few sharp distinctions in stem characters.

There is nothing new in the idea of using sorgo to make granulated sugar. All previous efforts, beginning when sorgo was first introduced about the middle of the past century, miscarried because of low yields, complicated by practical difficulties in processing the juice. Because of excessive amounts of starch and glucose in the juice, only a fraction of the sugar would crystallize. These early attempts were made before the principles of genetics were applied to plant breeding and when the conception of plant introduction and adaptation was in the "cut and try" stage, from which only now it is beginning to emerge. Although the purpose for which the plant was brought to America was not realized, sorgo became an important crop plant. During the Civil War and afterwards, it provided "long sweetenin' " in the form of thick sirup. More important, as a forage crop, sorgo occupies about 2 million acres in subhumid parts of the Great Plains.

An active revival of studies of sorgo for 'sugar production, based on new conceptions of plant introduction, modern plant-breeding methods, and improved sugar-processing techniques occurred in 1941, in cooperation with The South Coast Co., and the American Sugar Cane League, Inc. We cannot say yet whether the studies will lead to practical use of sorgo for sugar manufacture, but in any event the development of better varieties for sirup production, an integral part of the project that already is on the road to accomplishment, will justify the whole effort. The general breeding program for greater yields of better quality sorgo has assurance of success, the time of reaching that objective depending upon intensity of the program. Confidence in achieving the modest objective of specialized varieties for sugar production, yielding 20-ton crops of acceptable quality, is based on scientifically sound considerations of plant adaptation and upon progress made in following them.

There is little prospect of developing a sorgo-sugar industry independently of the already established sugar crops, beets and cane. The harvesting and processing season for sorgo would be far too short to justify the required large investment in processing machinery, which for efficient operation must be elaborate and therefore expensive. Production costs would be prohibitive. The sorgo harvesting season, however, does not overlap those of beets and cane, and an off-season supply of sorgo of good quality would be a welcome addition to keep beet factories or cane mills operating longer. The advantage to farmers and processors in leveling out their labor requirements is obvious. With a longer harvesting season attained by following sorgo with sugarcane, or sugar beets with sorgo in the areas where such sequence may be found possible, all operations may be conducted more efficiently and economically.

Another advantage of growing sorgo around central factories is that it would permit more economical use of valuable byproducts, like bagasse, the mass of material that remains after the juice has been pressed out of the stalks and is used in making lumber substitutes. The comprehensive resurvey of sorgo as a source of sugar and byproducts was prompted by the ever-present need for reducing sugar-production costs.

In general, the potential dispersal areas of domesticated plants are restricted to areas not drastically different in climate from their geographic centers of origin or the points of origin of their wild prototypes. This is especially true of the plants that must rely on seed production for their perpetuation. To the more familiar climatic requirements of plants, including appropriate levels of temperature, light, and water supply during a frost-free growing season, must often be added appropriate photo-period. Photoperiod is the relative duration of day and night, which differs at different latitudes and at different times of the year and profoundly influences the development of most plants, especially their production of flowers and seed.

Another fundamental requirement is the photothermal balance, which demands that at given temperatures there must be appropriate quotas of light. The complex, exacting, and usually interrelated requirements of Plants determine where the plants will grow. Unless the plants can be made to hybridize with related plants outside of the natural dispersal area, it is extremely unlikely that the area will be materially extended. There are exceptions in the case of short-lived annuals not sensitive to photoperiod ( day-neutral forms), but in general the colonizing or resettlement of domesticated plants is limited by these considerations.

There is no real acclimatization of plants as the term is generally understood. What passes for acclimatization ,in horticulture is merely the survival of adapted elements of heterogeneous plants in a new dispersal area. The environment of the new area must be compatible with some element already present in the plant, or that can be incorporated in the plant by crossing it with another plant. The dictionary definition of acclimatize, "to become habituated to a foreign climate," is misleading. But easy acceptance of that idea is the rule, fostered no doubt by apparent exceptions like the partial compensation of altitude for latitude and vice versa, "off-season" growing of plants in new areas, or artificially providing requirements such as shade, irrigation, and many others.