ABSTRACT
Introduction The sugar cane plant, Sacchararn officinarum L., is the most important source of
sugar in the world. It is a plant of great antiquity, originating, according to some authorities, in New Guinea, and according to others, in India. It spread to the Pacific Islands as early as the sixth millenium B.C. and later to the Middle East and the Mediterranean. It was introduced to the New World (first in Brazil and then in the Caribbean islands) mainly by the Portugese Jewish settlers who fled there to escape the Spanish Inquisition and has since flourished in the Philippines, Hawaii, and Australia, thus completing its migration around the world. Examination of a map of the world distribution of sugar cane reveals that it is mainly a tropical crop, growing in regions of substantial rainfall. Even in such regions, however, the irregularity of the rains and the length of the dry season are recognized as limiting factors in the growth of the cane, and interest has developed in supplementary irrigation. Along with this, the area of cultivation of sugar cane is being extended to semiarid and arid regions where full irrigation is a necessity. Along the desert coast of Peru and in northeastern Australia (Queensland) there are extensive plantations of sugar cane based almost entirely upon irrigation. As a result of this development, there has in recent years been an increase in the research on the irrigation of cane. Much of this research has, in the past, been conducted by people trained in horticulture and agricultural chemistry, with insufficient attention being paid to soil physics and to the engineering aspects of the problem.
Root System of Sugar Cane The sugar cane is propagated by the planting of a stem cutting from a mature plant,
called a sett or a seed. This is nourished by sett roots which quickly emerge from the original cutting. After a period of time, secondary shoots emerge from the ground alongside the original cutting and these send down shoot roots which eventually develop into the mature root system. The shoot roots, emerging from the lower ring of the shoot, are thin and markedly branched, but they eventually become thicker than the sett roots and the latter cease to function and die off. Sometimes three types of roots are described: the buttress roots, which originate from the basal nodes of the shoots and which support the plant; the superficial roots which are fibrous, thinner, more branched, and distributed through the upper 60 cm (2 ft) of soil, and which spread to a radius of 2 m around the plant; and the deep roots which are a ropelike mass of roots growing downward to great depths, limited only by the soil and moisture conditions. Under favorable conditions these may penetrate to as much as 6 m. Many studies have been made of the distribution of cane roots and the results vary with the local conditions. In Mauritius, for example, it was found that the vast majority of the fibrous roots which are most active in absorption occur in the upper 30 cm of the soil. They are most numerous between the radii of 1.00 and 1.20 m from the center of the plant. In Java, shoot roots were found distributed to depths of from 1 to 2 m. The factors which affect the root development are many, including the following: cane variety, soil depth, soil texture, fertility, moisture regime, temperature, wind, and cultivation practices. The factor of moisture regime is of special interest in the present chapter.
