AbstractA variety-fertilizer experiment using four varieties of sugarcane grown at seven different fertilizer levels was carried on for a plant cane and three ratoons at the Isabela Substation on a Coto clay. The major results were: (1) Nitrogen gave the highest yield increases in hundredweights of 96° available sugar per acre. (2) Phosphate fertilizers gave significant increases in yields of cane for the ratoon crops. (3) Potasium fertilizers did not increase the yield of sugar per acre. (4) Applications of nitrogen, phosphorus, or potassium did not significantly influence sucrose concentrations in the cane. (5) The leading two varieties, P.R., 902 and P.R. 905, gave significantly greater yields of sugar per acre than the other two varieties, P.O.J. 2878 and M. 28. (6) All varieties maintained their relative yielding power when tested at various fertilizer levels. (7) The reductions in yield from the omission of a fertilizer element for the mean of four crops were 22, 14, and 4 percent for nitrogen, phosphorus, and potassium, respectively. (8) Foliar analysis was made for leaves of the third ratoon only. Nitrogen values below 1.39-percent dry matter in the leaf represented definite deficiency, and response to nitrogen applications could be expected. Values of 0.16 percent of phosphorus in the leaf represented phosphorus deficiency, while there was no response to phosphates when the percentage was 0.20 or above. The potassium leaf values were above 2 percent and no yield responses were obtained at any potash level.
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