Potassium Fertilization Affects Growth, Nodulation, And Mineral Composition Of Leucaena Leucocephala

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Nitrogen fixing tree - Research reports Volume 13, 1995 Section 2. Contributed papers involving One NFT genus Pests related to pruning branches of Acacia mangium (Acacia) Pinhole beetle infestation of Acacia mangium logs (Acacia) Callus induction in explants of Acacia catechu (Acacia) Early growth of five Acacia species on Imperata cylindrica grassland (Acacia) Volume equations for Acacia crassicarpa (Acacia) Fertilizer effects on growth and nodulation of Albizia procera seedlings (Albizia) Growth of Casuarina equisetifolia and C. cunninghamiana in the Western Ghats, India (Casuarina) Casuarina cunninghamiana and C. equisetifolia provenance trial in Bangladesh (Casuarina) Growth and frost tolerance of Casuarina cunninghamiana in California, USA (Casuarina) Endomycorrhiza, rock phosphate, and organic matter effects on growth of Erythrina americana (Erythrina) A new insect pest of Erythrina poeppigiana in Costa Rica (Erythrina) Alimentary value of Gleditsia triacanthos seeds (Gleditsia) Pod yield of 16 accessions of Gleditsia triacanthos (Gleditsia) Gliricidia septum biomass production varies with plant row spacing and cutting height (Gliricidia) Root size distribution of a Leucaena leucocephala hedgerow as affected by pruning and alley cropping (Leucaena) Biology and control of Geotrichum sp., wilt pathogen of Leucaena leucocephala (Leucaena) Alley cropping maize with Leucaena leucocephala (Leucaena) Weed control effects of mulch from prunings of Leucaena leucocephala and Senna siamea (Leucaena) Photosynthesis by Leucaena leucocephala during water stress (Leucaena) Potassium fertilization affects growth, nodulation, and mineral composition of Leucaena leucocephala (Leucaena) Loss of cotyledons reduces survival of Pentaclethra macrophylla seedlings (Pentaclethra) Prosopis juliflora withstands extreme aridity and goat browsing in the Republic of Cape Verde (Prosopis) Seed storage container and protectant effects on viability and seed microflora of Sesbania sesban (Sesbania)

Potassium fertilization affects growth, nodulation, and mineral composition of Leucaena leucocephala (Leucaena) Paulino, Valdinei Tadeu, Marcia Atauri Cardelli de Lucena, Newton de Lucena Costa, and

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Maria Jose Valarini Introduction Leucaena leucocephala (Lam.) de Wit. has great potential for utilization in tropical agriculture, particularly in livestock production as a protein source and in enriching the soil, both of which uses rely on its capability for nitrogen fixation (Dreyfus and Dommergues 1981, Hogberg and Kvarnstrom 1982, Valarini and Bufarah 1984, Lucena and Paulino 1990). Its establishment and growth depend on an adequate supply of nutrients. Potassium fertilization often can dramatically increase yields of alfalfa and other forage legumes (Smith 1975, Collins and Duke 1981, Collins et al. 1986). A number of biochemical and physiological processes common to all plants require K (Collins and Duke 1981). Additionally, K can stimulate increases in legume N2 fixation by increasing availability of photosynthate to the nodules (Mengel et al. 1974, Duke et al. 1980). We evaluated the effects of K fertilizer application levels on leucaena shoot weight, nodulation, and NPK composition. Methods Plants were grown in pots containing 5 kg of an Ultisol from Rondonia State in the north of Brazil. The soil characteristics before fertilizer application were: pH (soil:water 2:1) 5.3, 2.0 ppm P, 2.2 meq/100g Ca + Mg, 0.3 meq/100g Al+3, and 74 ppm K. K level treatments were 0, 30, 60, 90, and 120 kg/ha K2O as KCl. P was applied at 49.5 kg/ha P2O5, as triple superphosphate. The experimental design was a randomized complete block with three replications. The leucaena seedlings were inoculated with rhizobia strains one week after germination. Shoots and roots were harvested after 180 days, and dry matter yield, number and dry weight of nodules, and concentrations of N, P, and K in plant tissue were measured. The plant response to the independent variable K was evaluated by regression analysis. Results Shoot weight and nodule number and weight showed response to K fertilization over the control (Table 1). Shoot weight increased with added K according to a quadratic regression (P c 0.01). Such a positive influence of K and other mineral elements on forage legumes other than leucaena was observed by Collins and Duke (1981), Collins et al. (1986), Cadisch et al. (1989), and Lucena and Paulino (1992). These studies indicated that K fertilization increases photosynthetic efficiency by improving translocation of photosynthate to roots. Compared with the control, the number and weight of nodules per plot (Table 1) increased linearly (b = 0.24 and 0.013, respectively) with K application. It is possible that the greater nodule numbers are related to the increase in root production, which may have provided more potential nodulation sites. Collins and Duke (1981) observed that the N2 fixation rate was increased considerably by K addition, not only by the increase in nodule number and weight but due to an enhancement of the movement of sugars from the shoot to the nodules.

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Table 1. Shoot and nodule dry weight and number of root nodules of Leucaena leucocephala fertilized with potassium.

Table 2. Plant uptake and leaf tissue content of N, P, and K of Leucaena leucocephala fertilized with potassium.

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Potassium addition linearly increased shoot K composition (Table 2) (b = 0.013), whereas it decreased N (b = -0.004) and P (P < 0.01) concentrations, probably due to a dillution effect from the large growth response to K. The decrease on shoot N concentration by K addition in leucaena and other legumes suggests that K effects are indirect, improving the performance of the legume and enabling greater N2 fixation. The mechanisms of the interaction of K on N2-fixation need further study. References Cadisch, G., R. Sylvester-Bradley, and J. Nosberger. 1989. 15N based estimation of nitrogen fixation by eight tropical forage legumes at two levels of P:K supply. Field Crops Res. 22:181-194. Collins, M., and S.H. Duke. 1981. Influence of potassium fertilization rate and form on photosynthesis and N2 fixation of alfalfa. Crop Sci. 21:481-485. Collins, M., D.J. Lang, and K.A. Kelling. 1986. Effects of phosphorus, potassium, and sulfur on alfalfa nitrogen fixation under field conditions. Agron. J. 78:959-963. Dreyfus, B., and Y. Dommergues. 1981. Relationships between rhizobia of a Leucaena and Acacia spp. Leucaena Res. Reports 2:43-44. Duke, S.H., M. Collins, and R.M. Soberalske. 1980. Effects of potassium fertilization on nitrogen fixation and nodule enzymes of nitrogen metabolism in alfalfa. Crop Sci. 20:213219. Hogberg, P., and M. Kvarnstrom. 1982. Nitrogen fixation by the woody legume Leucaena leucocephala in Tanzania. Plant and Soil 66:21-28. Mengel K., M.R. Haghparast, and K. Kock. 1974. The effect of potassium on the fixation of molecular nitrogen by root nodules of Vicia faba. Plant Physiol. 54: 535-538. Lucena, N.C., and V.T. Paulino. 1990. Response of Leucaena to single and combined inoculation with Rhizobium and mycorrhiza. Leucaena Res. Reports 11 :45-46. Lucena, N.C., and V.T. Paulino. 1992. Potassium fertilization affects Cajanus cajan growth, mineral composition, and nodulation. Nitrogen Fixing Tree Res. Reports 10: 121122. Smith, D. 1975. Effects of potassium topdressing a low fertility silt loam soil on alfalfa herbage yields and compostion and on soil K values. Agron. J. 67:60-64. Valarini, M.J., and G. Bufarah. 1984. Resposta de leucaena a inoculacao comparada a diferentes tratamentos fertilizantes. Pesq. Agrop. Bras. 19:275-279.

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