Ratoon Cropping of Sorghum: I. Origin, Time of Appearance, and Fate of Tillers

This study was conducted to understand the basic growth patterns and tillering behavior of sorghum (Sorghum bicolor (L.) Moench) from plant crop to succeeding ratoon crops in order to attain maximum production with minimum tillage using a particular practice such as ratooning. Under this system, it is possible to have several harvests from a single planting. Time and location of tiller appearance and survival of tillers are important factors in determining the number and vigor of productive tillers which, in turn, influence the growth, development, yields, and longevity of ratoon crops. Successive tiller production and death of tillers affect the perenniality of the crop. Three cultivars of sorghum ‘Mini-milo Br 54’, NK 222A, and NK 300 were grown under three plant populations [P₁ = 5, P₂ = 10, and P₃ = 20 plants per 3.7 liter (5-gal.) pot] and were observed for tillering behavior in relation to the place of origin, time of appearance, duration of early tillers, and to grain and stover yields. Tillers that sprouted early (first and second tillers) originated from basal nodes of the plant. Later tillers (third, fourth, and so on) developed from the nodes adjacent to elongated internodes. Not all tillers which developed, however, reached maturity. Usually the first two tillers died. Tillers developed earlier in lower populations (P₁ and P₂) than in the higher population, P₃. Cultivar NK 222A produced only two tillers per plant in each population. Compared with tillers of ratoon crops, it took a longer time for the two early tillers of the plant crop to die. Tillers that developed on the upper parts of the stubble were more susceptible to breakage. More tillers were produced during the plant crop, and the number declined in each succeeding ratoon crop. High plant populations resulted in development of few reproductive tiller, less uniformity in plant height, and a delay in tiller formation. In spite of this condition, increased plant population resulted in increased grain and stover yields. More plants per unit area compensated for the production of fewer tillers. Mini-milo Br 54 produced the highest number of tillers per plant, followed by NK 222A, and then NK 300 in the first population. Understanding the basic growth patterns and tillering behavior of a particular sorghum variety, therefore, facilitates management of ratoon crops for maximum production.