Ratooning

Ratooning is the agricultural practice of harvesting a monocot crop by cutting most of the above-ground portion but leaving the roots and the growing shoot apices intact so as to allow the plants to recover and produce a fresh crop in the next season. This practice is widely used in the cultivation of crops such as rice, sugarcane, banana, and pineapple. Ratoon crops cannot be perennially renewed, and may be harvested only for a few seasons, as a decline in yield tends to occur due to increased crowding, damage by pests and diseases, and a decline in soil fertility. Ratooning is the agricultural practice of harvesting a monocot crop by cutting most of the above-ground portion but leaving the roots and the growing shoot apices intact so as to allow the plants to recover and produce a fresh crop in the next season. This practice is widely used in the cultivation of crops such as rice, sugarcane, banana, and pineapple. Ratoon crops cannot be perennially renewed, and may be harvested only for a few seasons, as a decline in yield tends to occur due to increased crowding, damage by pests and diseases, and a decline in soil fertility. The word 'ratoon' probably owes its origin either from the Latin words retonsus, meaning 'to cut down' or retono, which means 'to thunder back' or 'resound'. In Spanish, the close words retoño (retoñar) mean 'sprout' ('to sprout'). Ratooning is an ancient method of propagation in sugarcane in which subterranean buds on the stubble (the part of cane left underground after harvesting) give rise to a new crop stand, which is usually referred to as the 'ratoon' or the 'stubble crop' as opposed to 'plant crop', which is raised from seeds or seedlings. Ratooning reduces the cost of cultivation by dispensing with additional seed material and some cultural practices such as land preparation and preparatory irrigation (palewa). It also results in early ripening of canes by at least a month or so, thus it adds to the effective crushing period. Sugarcane has a tremendous ratooning potential, and the oldest cultivated ratoon, being ratooned since 1757, in East China, in Fujian Province, stands to its testimony. The number of ratoons in sugarcane production cycles varies throughout the world, i.e., from one plant crop in Indonesia and some parts of China, one plant crop and a ratoon crop in India, Fiji and some parts of China, to six or more successive ratoons in Mauritius, Cuba, Venezuela, clayey soils of Zimbabwe, some parts of Puerto Rico, etc. The later is also referred to as multiple ratooning. A decline in cane yield in successive ratoon crops, the ratoon decline, on the order of 20%, had been reported from many sugarcane-growing areas in India; the decline is more (up to 40% ) in subtropical India. Causes for this decline are: poor ratoon management, inherited differences in potential (ratoon) productivity, increasing incidence of diseases (like smut, grassy shoot disease, and red rot) which result in stands with gaps (studies conducted in India have shown that a gap over 10% significantly affects productivity of a ratoon crop), relatively less efficient enzyme systems (particularly nitrate reductase activity, in vivo and prevalence of low temperatures during harvest, especially for early-ripening varieties and ratoon crop(s) in subtropical India which affects sprouting of stubble buds, etc. Insect pests also assume importance in a ratoon crop as: stubble acts as a 'carry-over' of the inocula of pests both for coming up ratoon and for the neighbouring sugarcane crop(s), improperly looked-after crop gets infested by a number of insect pests, emerging sprouts of a ratoon crop favour rapid development and multiplication of some of the insect pests, and insect associated with stubble affect sprouting causing gaps which ultimately affect productivity of the ratoon crop, per se. In Indian context, in subtropical India, ratoon initiated during spring (March) resulted in higher number of millable canes, cane yield and sucrose % juice in comparison to ratoon crops initiated either in winter (January) or summer (May). In peninsular India, however, as the sugarcane crop does not suffer extremes of weather conditions during summer and winters, differences in time of planting and harvest do not significantly influence the yield of succeeding ratoon crop. Such a decline could be effectively prevented by proper ratoon management. Need for the latter stems from the famous Kalai (Aligarh, India) experiments conducted during 1939-1949. A good example of ratoon management and multiple ratooning is from Hoshalli village ( in district Shimoga, Karnataka, India) where good yields of sugarcane ratoon crop (125-134 t/ha) were harvested year after year since 1968 without much loss in cane yield and quality. The crux for such a success was trash mulching, application of lime and irrigation after harvest of the crop every year. Ratooning has now become so much important in sugarcane production system that ratooning ability has become one of the important selection criteria for release of sugarcane varieties for commercial cultivation. Besides sugarcane, ratooning is also practiced commercially in many other crops like banana, pineapple, pigeon pea, sorghum, rice, cotton, ramie, mint, etc.. Rice is grown as a monocarpic annual plant. However, in tropical areas it can survice as a perennial, producing a ratoon crop, and may survive for up to 30 years. The earliest record for ratooning, in a crop plant, could be traced back to the Vedic period in India, wherein, in Atharvaveda, there is mention that the farmers cultivating barley (yava) used to cut barley plants many a times ( 20/125/2, Richa or Shloka No. 5755). Ratooning is most often used with crops which are known to give a steady yield for three years under most conditions. For example, the woody desert shrub guayule, an alternative source of natural rubber, is first harvested at two years, then ratooned annually in spring with a final crop that includes both tops and roots. Yield of ratoon crop is a function of yield potential and its ratooning ability. The latter, by and large, envisages the extent of multiple ratooning and their relative yield performance as compared to corresponding plant crop In India sugarcane varieties cultivated prior to introduction of Co varieties were not rationed because of their susceptibility to insect-pests and diseases. Incorporation of S. spontaneum genome into modern sugarcane varieties has contributed to ratooning ability. The latter has been assessed by dry matter production of above ground parts at periodic harvests (at 4 months intervals), the ratio of performance ( of NMC and/ or cane weight) of ratoon crop vs. plant crop. Characters like higher plant cane yield, stalk population and sprouting of stubble buds are useful in selecting good ratooners. Ratoon x environment interaction were high in varieties with poor ratooning ability and inherited differences in potential productivity appear to be responsible for ratoon decline. In Jamaica to calculate decline in ratoon productivity a Ratoon Performance Index (RPI) is used. In India, the second major sugarcane growing country, among the sugarcane varieties released and notified from 2000 to 2015 for commercial cultivation Co 85004, Co 2001-13, Co 2001-15 Co 0218, Co 0403, Co 86249, Co 0237, CoPk 05191 are good ratooners and CoPant 90223, CoS 95255, CoS 94270, CoSe 92423 have been rated to be the excellent ratooners.