1910.] EXPERIMENTS ON YAM CULTIVATION. 171 



As regards the planting distance the results this year as last show 

 that a lai-ger yield is obtained with close planting. Holes four feet by 

 two feet and four feet by three feet gave yields of 9-32 and 9-67 tons 

 as against 14-15 and 14-56 tons per acre from holes three feet by two 

 feet and three by three feet respectively ; a larger profit per acre has 

 also been obtained from the closer planting, similarly the yield from 

 trenches four feet apart planted at distances of three, two and one and 

 a half feet was 8-15, 10-34 and 12-05 tons as against 14-61 and 15-32 tons 

 per acre from trenches three feet apart planted at distances of one foot 

 and eighteen inches apart. It should be mentioned however, that it has- 

 been found awkward to make holes three feet, by two feet and four feet 

 by two feet apart, the nearest convenient distance at which these can 

 be made is three feet by three feet, moreover it is with holes at this 

 distance that the best results have been obtained. The best distance 

 for trenches is three feet apart and the plants may be put at two, one 

 and a half and even one foot apart. The extra value of the plants 

 and planting one foot apart in trenches three feet apart is 

 539 38 more than when the plants are put in eighteen inches apart 

 and an increased yield of 12 cwt. per acre would be required to 

 cover this extra cost. 



The question as to whether trenching is more profitable than holing 

 is not so easily answered. Trenching is more expensive thin holing 

 but as it permits of closer planting, a higher yield is usually obtained 

 vide plots 12 and 13 as compared with plots 5 and 6, also plots 9, 10 

 and 11 compared with plots 7 and 8. With trenching the land is better 

 prepared for subsequent crops, especially if the untrenched portion of 

 the first year is worked up for the second year. Holes three feet by 

 two feet and three feet by three feet gave a profit of $642 44 and 

 $726 28 per acre respectively ; trenches three feet apart planted at 

 distances of one foot and eighteen inches gave a profit of $653 21 and 

 5647 50 per acre respectively. 



The usual practice in Trinidad is to stake the yam vines after they 

 have grown from three to four feet long and the opinion has been 

 expressed by several that staking is essential to obtain a large crop, the 

 idea being that with our heavy rainfall and damp climate the vines 

 would rot especially if injured when weeding or moulding the plants. 

 With the object of ascertaining the correctness of this opinion two 

 plots have been trie 1 this year without staking in trenches three feet 

 apart planted at distances of one foot and eighteen inches. The results 

 are shown under plots 14 and 15 as compared with plots 12 and 13 

 where the vines were staked. The uiistaked plots have given a yield 

 of 16-03 and 10-58 tons as against 15-32 and 14-64 tons per acre from 

 the staked plots. Although the results of this first experiment are not 

 conclusive a higher yield having been obtained in one plot from the 

 unstaked and in the other from the staked plot— they tend to show 

 that as large a yield may be obtained without staking as from staking 

 the vines. As "the cost of staking is by no means negligible it may be 

 found in subsequent experiments to hi more profitable to dispense with 

 staking. 



