The third main phase of the sorgo investigation, consisting of widespread indicator, or test, plantings, was started in 1942 and continued through 1945. Obviously the tests were restricted to the so-called domestic varieties because hybrids resulting from fresh importations were not available. The purpose was to get an indication of comparable expected yields especially in districts where farmers grow beets and sugarcane commercially to determine possibilities of growing the crops in combination. A representative selection of sorgos was used, including one or more varieties known to grow reasonably well in each district. The pattern of the test and the varieties were identical in each of the districts, which were in Michigan, Minnesota, Nebraska, Utah, California, Louisiana, Mississippi, Georgia, and Florida.

The test plantings almost everywhere confirmed that the old-established varieties are not promising for sugar production, the yields per acre and quality of juice being unsatisfactory. But the plantings permitted evaluation of the different sections of the country for sorgo-sugar production. The lower latitudes and lower elevations are, generally speaking, superior for the purpose. With present varieties, and presumably with varieties improved to the extent that can be visualized, the Middle West and Intermountain areas are not suitable. The assumption is made on good grounds that the tropical hybrids now in process of development will be even more definitely restricted to the lower latitudes and elevations. In Climatic and environmental requirements they will doubtless demand conditions intermediate between those suitable for the present sirup varieties and subtropical conditions existing farther south. Prospects for the Gulf States are reasonably good. Under irrigation in the sugar-beet areas of southern California the most promising indications for sorgo-sugar production were obtained. The results of test plantings in the Imperial Valley were:

Tons of stalks Indicated 96°

Variety acre sugar per acre
(in pounds)

In this report of progress, no definite forecast can be made as to the outcome of investigations on using sorgo to make sugar. The performance of sorgo in the test cited is impressive. The prospects are brighter with the promise of better adapted varieties now in process of development. Sugar beets and sugarcane yield more sugar per acre and there is a temptation to compare harvest results directly, but it should be emphasized that in terms of sugar increment per month, sorgo even now compares favorably with the other sugar plants that require much longer crop seasons.

THE AUTHOR

E. W. Brandes was one of the organizers of the International Society of Sugar Cane Technologists in 1924, and has directed various scientific explorations in Central and South America, Asia, Africa, and the Pacific islands. At the present time he is in charge of the Division of Sugar Plant Investigations of the Bureau of Plant Industry, Soils, and Agricultural Engineering.