The authors carried out studies to evaluate the degree of drought injury and its effect on summer-planted sugar cane cultivated in different soils.
The soils investigated were “Shimajiri-marji” (Mabuni series soil) and “Jargaru” (Inamine series soil) which are both the main soils on Okinawa island. The variety cultivated in the study was NCo 310, which is one of the commercial varieties in Okinawa Prefecture. The following results were obtained.
1. For almost all the parameters studied, the growth of sugar cane, in the earlier growth stages, was better at Uebaru and Kiyanbaru, both with Shimajiri-marji soil, than at Nagatabaru with Jargaru soil. In the later growth stages, however, the growth was better at Nagatabaru than at Uebaru and Kiyanbaru.
2. At the time of harvest, stalk weight per squre meter, average one stalk weight, stalk length, and stalk number per squar meter were all lower at Uebaru than at Nagatabaru.
3. It is considered that the growth of sugar cane in Shimajiri-marji soil was less satisfactory than that in Jargaru soil at the later growth stages due to the small amount of precipitation. Indeed, it may be very difficult for sugar cane roots to grow deep into Shimajiri-marji soil in a year with little rainfall, since the arable soil is shallow and the subsoil is hard. Besides, it can be assumed that drought injury must have been severe since capillary water supply from groundwater was also inadequate in Shimajiri-marji soil.
4. Because of the wilting and death of leaves resulting from the inadequate supply of water, low values of leaf area and LAI were recorded at Uebaru.
5. CGR showed a higher correlation with LAI than with NAR. This phenomenon may be related to the fact that in this experiment the LAI of plants in each field was smaller than the optimum LAI.

View full abstract

[in Japanese]

View full abstract

In case of transplanting 22 hills or 27 hills per m² can be taken as an optimum planting density for maximum yield, and in case of direct sowing any amount of seed per ha within a range of 50 kg to 100 kg can be taken as an optimum seeding density. No significant difference in yield is found among the ordinary transplanting method, the broadcast transplanting method, the ordinary transplanting method using broadcastable seedlings and the direct sowing method.

View full abstract

Leaves, racemes or lateral buds were removed to see (1) the interrelation between the branches and the primary raceme and (2) the role of a certain leaf on the growth of branches and the ripening of the raceme of castor plants. First and second leaf removal inhibited the growth of first and second node branches and the ripening of the primary raceme, and promoted third node branching. Third and fourth leaf removal inhibited growth of the first, second and third node branches but did not affect the ripening of the primary raceme. Primary raceme removal had no effect on first and second node branching, but promoted third node branching. Lateral bud removal increased the number of capsules, the number of seeds and the seed and oil yield of the primary raceme, while increasing the acid value of the oil because of delayed ripening.

View full abstract

The complete process of differentiation and development of lateral buds in castor plants was observed. Lateral buds differentiated in ascending order. The nth node lateral bud differentiated synchronously with the differentiation of the (n+3) th leaf on a main stem before the differentiation of the primary raceme. The three uppermost buds differentiated synchronously with the differentiation of the primary raceme. The two or three uppermost buds developed into bearing branches.

View full abstract