AREA AND YIELD 



DIOSCOREA 



Cultivation 



Alongside is soured a stake (usually a bamboo) perhaps 8 to 15 feet in staking. 

 bright above ground, and it is customary to bind these together at the 

 top iii dusters of four. It is also not unromnion to ^row special trees 

 on \vhirh the climbing stems of the yams may be trained. When this 

 is the cist- pits are dug alongside of the trees and filled with m-v. 



and inai.iiiv and the sets deposited within these. Occasionally (as, for 

 i tuple, in Bihar) tin- plants are allowed to trail on the ground, but 

 tin- yield is believed to be then smaller. In the West Indies, however, 

 in is dftcii treated in this way, and apparently with satisfactory 

 results. It is also affirmed that in China the trailing stems are pegged Trailing, 

 or layered into the ground, and thus caused to root, the result being 

 it tubers are formed at the new points of growth. With certain 

 j, having a rhizome-like underground stem and one or two large 

 tubers, the lower edible portion is cut off and the upper rhizome planted 

 for next, year's growth. This, however, is rather the careful system 

 pursued with wild yams than a regular method of agricultural propaga- wild stock, 

 ion. Planting is done in April and the crop comes into season about seasons. 

 )ecember. This is the usual practice, but a wide range of seasons exists 

 direct adaptation to local conditions and the species of plant grown. 

 uis in Arcot it is said the yam is cultivated in January and harvested 

 August and September. In the Konkan yams are sometimes grown 

 done and the crop comes into season about October. In Upper India, 

 :cording to Duthie and Fuller, the tubers of />. Imlhifera are planted 

 in May and June and dug up every three years. Of />. <ilnt<i. var. 

 sa. these authors say it is planted in June and the crop gathered 

 ic following February. 



Yield. The yield depends largely on the plant grown, the nature of Yield, 

 climate and soil, the degree of cultivation, and the proportion of the pro- 

 duce treated as edible. The yield has been variously put at from 3 to 

 10 tons an acre, or approximately the same as the yield of potatoes. 

 But yams are in India most frequently a supplementary crop to ginger, supplementary 

 turmeric, brinjal, sweet-potato or maize. Yams are moreover more 

 nutritious than ordinary potatoes, so that the combined produce may be 

 accepted, from the standpoint of food supply, as highly satisfactory. 



Chemistry. Bhaduri (Rept. Labor. Ind. Mus. (Indust, Sec.), 1902-3, 25) 

 says the acridity of yams is due to the presence of needle-shaped crystals 

 of calcium oxalate, and the poisonous property to the presence of the 



Kilkaloidal principle Dioscoreine first isolated by Boorsma of Java. Hooper 

 I.e., 1903-4, 32) gives the results obtained during the examination of 

 ome forty kinds of these tubers. The poison was found most abun- 

 dant in I>. <l<rinoini, but was often present in I). Initbifera and 

 It. ji<'iif<tj)hi/ff<i. "The average amount of moisture in fresh tubers 

 was 80 per cent., and the average percentage composition of the dried 

 tubers was : fat 1'02, albuminoids 10-87, carbohydrates 77*01, fibre 

 5-16, ash 5-94, and nitrogen 1'73. The starch of the yams was examined 

 microscopically and 'certain species were found to have characteristically 

 shaped granules, which distinguished them from other species." 



[<?/. De Candolle, Orig. Cult. Plant*, 1884, 76-81 ; Asa Gray, Scient. Papers, 

 1889, i., 322-6; Mollison, Handbook Ind. Agri., 1!01, iii., 197-200; Mukerji, 

 Handbook Ind. Agri., 1901, 203, 467, 477 ; Morris, West. Ind. Yams, Imp. Dept. 

 Ai/ri., 1902, No. 18; Nicholls, Textbook Trap. Agri., 1892, 284-8; Firminger, 

 Man. Qard. Ind. (ed. Cameron), 1904, 140-2 ; Notes on Dioscoreas Cult, in Roy. 

 Bot. Gard., Ceylon, in Circ. and Agri. Journ., 1905, iii. 1-9.] 



497 32 



Crop. 



