Formas de potássio e estabelecimento de nível crítico para alguns solos do estado de Minas Gerais
I: Potássio disponível
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formas de potássio, crescimento vegetal, concentração de hidrogênio, capacidade de campo, correlação estatísticaResumo
This study was conducted to determine the relationships between available potassium level and vegetative growth.
For this study twenty soils were selected from six different locations within the State of Minas Gerais. These Soils were classified as follows: nine red-yellow podzolic; Six dark latosols; four red-yellow latosols and one hidromophic. They were analyzed for texture, usable water, pH, organic matter, eschangeable bases and type of clayey material. The level of available potassium was also determined using following extractors: North Carolina 1:10 and 1:4; Bray 1 and 2; Morgan; 0,05N sulfuric acid and 0,05N nitric acid.
Italian millet (Settaria italica Beauv.) was planted in 2 Kg samples of soil to which increasing quantities of potassium had been added, for the nvurpose of obtaining data using plants. The plant material was harvested 40 days after planting. It was weighed and analyzed for percentage potassium in the aerial plant material, the potassium absorved by the plant and the per cent yield of plant material.
The results obtained permitted the following conclusions:
1. The levels of available potassium varied according to the extractant and soil class. The variation due to the extractant was related to the ratio of soil to solution and the concentration and type of anion.
2. The available potassium levels obtained with the different extractante were correlated significantly.
3. The available potassium content was correlated with the yield data, adsorved potassium and percent potassium in the aerial plant material. The largest coefficient of correlation was obtained with the North Carolina 1:4 extractor.
4. The critical levels obtained using the various extrac- tant varied with the extractants as: Bray 2 (63,4 - 65,5 ppm); Bray 1 (55,5 - 65,5 ppm); 0,05 HNO3 (39,8 - 51,5 ppm); North Carolina 1:10 (56,2 - 81,1); HpS03 0,05N (63.4 - 74.1 ppm); Morgan (62,4 ppm) and North Carolina 1:4 (45,0 - 47,0 Mi
Referências
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BRAY, R.H. Correlation of soil tests with crop response to added fertilizers and with fertilizer requeriments. In, Kitchen, H. b. ed. Diagnostic Technique for soils and crops. Washington, The American Potash Inst., 1948. pp. 53-85.
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REID, P.H. & COPELANO, C. Analytical methods used by the Soil Testing Division. Raleigh, North Carolina Depart- ment of Agriculture, 1969. 19 p. mimeo.
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