AbstractPlantains, cultivar Maricongo, were grown on a Humatas clay (Typic Tropohumults) in the humid mountains of Puerto Rico. Plants fertilized with 678 kg/ha of a 10-5-20 (N-P2O5-K2O) fertilizer were sampled monthly from planting to harvest. There was only a small production of dry matter in the first 5 months of growth. Thereafter, growth progressed rapidly giving large increases in dry weight and plant height. Dry matter of the whole plant fluctuated from 5 to 6% for the first 10 months and then increased, peaking at 9% at 13 months, when harvested. The fruit averaged 32.6% dry matter. Leaves had a higher percentage of dry weight than pseudostem until 6 months of age. From 7 to 10 months, weights were similar. Thereafter, pseudostem weights were greater. Dry weight percentage of leaves was about three times that of pseudostems. The percentages of N and P were higher in the leaf than in the pseudostem at all stages of growth; the reverse was true for K. The NPK levels tended to decrease with increasing age of the plant. The leaves had a higher nutrient uptake rate than the pseudostems in the early stages of growth for N and P, but not for K. Ca and Mg levels indicated no clear difference between leaves and pseudostems. There was a trend for reduction in Mg content of the leaves with increasing age, and both leaves and pseudostems showed a definite drop in Mg level at the fruiting stage. The ratios of leaves to pseudostems for nutrient uptake at harvest were N, 1:.1; P, 1:1; K, 1:4; Ca, 1:2; and Mg, 1:2. Based on 2,988 plants/ha, a crop of plantains removes 70 kg of N, 9 of P, 242 of K, 2 of Ca, and 11 of Mg. In turn, left behind in the fields in pseudostems and leaves, were 262 kg of N, 13 of P, 1,471 of K, 208 of Ca, and 45 of Mg, which were retu rned to the soil.
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