Effects of different levels of N, P and K fertilization on the growth and yield of upland and lowland taro (Colocasia esculenta (L.) Schott, var. Lehua)

De la Pena, Ramon S (Ramon Serrano), 1936
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Nitrogen, phosphorus and potassium were applied separately from 0 to 1120 kg/ha to upland and lowland taro. A 2 x 2 x 2 N-P-K interaction experiment was also conducted in pots using 0 and 15 grams of each element per plant. Nitrogen fertilization increased the N contents of the taro leaves but decreased both the P and K contents. Applications of P fertilizer increased the P content in the leaves but decreased the K content. Potassium fertilization increased K and decreased Ca and Mg contents of the taro leaves. The N content of upland taro leaves increased with K fertilization but the N content of the lowland taro leaves decreased. Potassium in the leaves of lowland taro regardless of treatments was lower than the K content of upland taro due to the higher Ca and Mg contents of the lowland soil. Both upland and lowland taro plants exhibited luxurious P and K consumptions. The N, P, and K contents of the leaves, regardless of treatments, decreased with age ..• The total N content of the soils was negatively related to the N fertilization, while soluble P and exchangeable K were directly related to the rates of P and K fertilizers applied. Yields of both upland and lowland taro were significantly increased by N and P fertilization. Potassium fertilization increased the yields of upland taro only. Delayed harvesting up to 15 months increased the yields of lowland taro, while yields of the upland taro at 12 to 15 months old did not differ significantly. In the lowland taro, the significant yield increase due to fertilization was attributed to the increase in number and weight of the sucker corms. In the upland taro, however, yield differences among fertilized plots were attributed to the main corms. Nitrogen fertilization decreased the density of both upland and lowland taro corms significantly. Phosphorus fertilization did not have significant effects on the corm density. Potassium fertilization increased the corm density, especially in the lowland. Protein content of the corms of upland and lowland taro which were fertilized with N increased by 53.5% over the control. In the pot experiments, the increase in protein content was 250%. The P and K contents of the corms also increased with P and K fertilization. In the pot experiment, only N fertilization gave significant increases in the weights of the corms, roots and leaves of the plants. Nitrogen deficiency was observed in all plants which did not receive N fertilization. Analysis of the leaves showed that plants which received N had an average of 2.8% and 4.6% N in the petioles and blades, respectively, compared with 1.1% and 3.3% N in the petioles and blades of plants without N fertilization. No P and K deficiencies were observed. The N, P, and K contents of the individual leaves showed a tendency to decrease from the youngest leaf to the oldest, except for P which increased from the youngest to the oldest when the P supply was not limiting. Results of the experiments showed that soil and plant analysis can be used to evaluate the fertilizer requirements of taro. In soil analysis, however, other methods of extracting soil N should be used to give a reliable index for the N requirement of taro.
Thesis (Ph. D.)--University of Hawaii, 1967.
Bibliography: leaves 156-169.
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Taro -- Yields, Taro -- Fertilizers
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Theses for the degree of Doctor of Philosophy (University of Hawaii (Honolulu)). Agronomy and Soil Science; no. 126
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