Tillerlng capacity and behavior determine the success or failure of ratoon cropping in grasses. This work was initiated to gain more understanding on the seasonal effects on tillering and ratoon cropping of sorghum [Sorghum bicolor (L.) Moench] in the high rainfall tropics by studying the effects of various daylengths and temperature regimes on plant growth and development and yields of ratoon crops. Sorghum plants were grown under two daylengths and four temperature regimes in controlled‐environment chambers. Temperatures and daylengths used simulated tropical winter and summer conditions similar to rainfed sugarcane (Saccharum officinarum L.) plantations of Hawaii where ratoon sorghum has been grown. It is contemplated that sorghum could be used as an alternate crop for sugarcane plantations phasing out of production and that ratooning the crop could be utilized as a management practice, thus reducing the high cost of production. An interaction between photoperiod and temperature was observed. With low temperature (23.9 C‐day/15.5 C‐night) and short day (10 hours), fewer tillers/plant were produced resulting in the development of fewer reproductive tillers. At the same low night and day temperatures, but with photoperiod increased from 10 to 14 hours, more tillers/plant, more reproductive tillers/plant, greater leaf area, more leaves, more numerous but shorter internodes, and longer panicles were produced. The check plants grown outside produced more reproductive tillers/plant than the various treatments. Increasing both the temperature (32.2 C‐day/23.9 C‐night) and daylength (14 hours) resulted in further increase in tiller number/plant, leaf area, and internode number. Higher temperature and shorter daylength tended to bring about early maturity. Low light intensity, short photoperiod, and low temperature, resulted in rosette form of foliage with very short internodes and reduced number of leaves. This condition led to low grain and stover yields.

The perennial habit of sorghum, Sorghum bicolor (L.) Moench, in a tropical climate permits the production of successive harvest of seed crops from an initial planting. Cultural treatments involving tillage and fertilization to favor such practice are termed ratooning. The objective of this study was to determine the effects of the various N rates and cutting heights on ratoon crops of sorghum at different seasons in relation to tillering behavior, yields, and other agronomic characteristics. Recognizing these effects would facilitate the timely application of the right amount of N fertilizer and proper cutting height to be done on ratoon crops. The performance of ratoon crops of grain sorghum, Sorghum bicolor (L.) Moench, ‘Pride 550 Br’, was studied as affected by four N rates (0, 100, 200, and 250 kg N/ha as urea) and three cutting heights (3, 8, and 13 cm) in the field in Hawaii. Performance characteristics studied were tillering behavior, yield and yield components, plant height, days to heading and maturity, and total plant N content. One half of the N was applied when the seedlings were about 3 weeks old; the other half side‐dressed at early booting stage. Generally, in the plant crop and ratoon crops, more tillers, larger leaf area, larger stalks, larger heads with more and heavier grains, and taller plants, and therefore, increased grain and stover yields were produced with higher N treatments up to 250 kg N/ha. Application of 100 kg N/ha increased the total plant N (percent) and further application of N (200 and 250 kg N/ha) increased the N concentrations in the plant from the first to the third ratoons. In the fourth ratoon and in Kilauea planting, total plant N did not increase despite N applications. Although yields increased as the amount of N increased, a leveling off or decline in yields at high N rates, occurred, indicating that optimum N rates were reached in this study. During winter, highest yields were produced with 200 or 250 kg N/ha and when plants were at the 13‐cm cutting height. In summer, higher yields were produced with the same N rates but lower cutting heights (3 and 8 cm). Based on this study, it is recommended that to obtain high grain and stover yields during winter and summer, 200 to 250 kg N/ha be applied to ratoon crops harvested at 13‐cm and 3‐ and 8‐cm cutting height, respectively.

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.

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Three species of legumes such as mungbean, cowpea, amd bushbean were incorporated into the soil at flowering to later stages of growth namely; after 1st, 2nd, and 3rd priming operations. These were followed by two croppings of upland rice. Significantly lower soil bulk densities were obtained after the first crop of rice when mungbean and bushbean herbage were used as green manure. The pH, O.M., P and K contents of the soil planted to rice were not markedly affected by the species and timing of field legume incorporation. Interaction effects between the two variables on O. M. and pH were noted after the harvest of the first and second crops of rice, respectively. Most of the growth and yield parameters of both crops of rice were not significantly influenced by the treatments involved. [his indicates the feasibility of modifying the usual practice of green manuring at flowering stage to later stages of growth using grain legumes without necessarily sacrificing their expected yields. Cowpea was the most suitable green manure crops for upland rice. Its use resulted in the highest combined net income for two croppings of rice, generating PhP 48,698.98 ha-1 or PhP 2.12 income per peso invested. Regardless of field legumes used, herbage incorporation after the first priming generated an income of PhP 1.56 per peso invested while green manuring at flowering stage gave only PhP 0.69.