Resumo
1. The present work was carried out to study the effects of mineral nutrients in the yield as well as in the composition of cassava roots. The variety "Branca de Sta. Catarina" was grown by the sand culture method, the following treatments being used: N0 P0 K0, N0 P1 Kl, N1 P0 K1, N2 P1 K0, N2 P1 K1, N1 P2 K1, and N1 P1 K2, where the figures 0, 1, and 2 denote the relative proportion of a given element. The nutrients were given as follows: N = 35 grams of ammonium nitrate per pot loaded with 120 pounds of washed sand; P1 = 35 grams of monocalcium phosphate; Kl = 28 grams of sulfate of potash. Besides those fertilizers, each pot received 26 grams of magnesium sulfate and weekly doses of micronutrients as indicated by HOAGLAND and ARNON (1939). To apply the macronutrients the total doses were divided in three parts evenly distributed during the life cycle of cassava. 2. As far yield of roots and foliage are concerned, there are a few points to be considered: 2.1. the most striking effect on yield was verified when P was omitted from the fertilization; this treatment gave the poorest yields of the whole experiment; the need of that element for the phosphorylation of the starchy reserves explains such result; 2.2. phosphorus and nitrogen, under the experimental conditions, showed to be the most important nutrients for cassava; the effect of potassium in the weight of the roots produced was much less marked; it is noteworthy to mention, that in absence of potassium, the roots yield decreased whereas the foliage increased; as potassium is essential for the translocation of carbohydrates it is reasonable to admit that sugars produced in the leaves instead of going down and accumulate as starch in the roots were consumed in the production of more green matter. 3. Chemical analyses of roots revealed the following interesting points: 3.1. the lack of phosphorus brought about the most drastic reduction in the starch content of the roots; while the treatment N1 P1 K1 gave 32 per cent of starch, with NI PO Kl the amount found was 25 per cent; this result can be explained by the requirement of P for the enzymatic synthesis of starch; it has to be mentioned that the decrease in the starch content was associated with the remarkable drop in yield observed when P was omitted from the nutrient medium; 3.2. the double dosis of nitrogen in the treatment N2 P1 K1, gave the highest yields; however the increase in yield did not produce any industrial gain: whereas the treatment N1 P1 K1 gave 32 per cent of starch, by raising the N level to N2, the starch content fell to 24 per cent; now, considering the total amount of starch present in the roots, one can see, that the increase in roots yield did not compensate for the marked decrease in the starch content; that is, the amount of starch obtained with N1 P1 K1 does not differ statistically from the quantity obtained with N2 P1 K1; as far we know facts similar to this had been observed in sugar beets and sugar cane, as a result of the interaction between nitrogen and sugar produced; the biochemical aspect of the problem is very interesting: by raising the amount of assimilable nitrogen, instead of the carbohydrates polymerize to starch, they do combine to the amino groups to give proteinaceous materials; actually, it did happen that the protein content increased from 2.91 to 5.14 per cent.
ISecção de Química Agrícola, E. S. A. "Luiz de Queiroz", Univ. de S. Paulo, Piracicaba, Estado de S. Paulo, Brasil
IISecção de Fitotecnia, E. S. A. "Luiz de Queiroz", Univ. de S. Paulo, Piracicaba, Estado de São Paulo, Brasil
IIISecção de Tecnologia Agrícola, Instituto Agronômico do Estado de S. Paulo, Campinas, Estado de São Paulo, Brasil
SUMMARY
1. The present work was carried out to study the effects of mineral nutrients in the yield as well as in the composition of cassava roots. The variety "Branca de Sta. Catarina" was grown by the sand culture method, the following treatments being used: N0 P0 K0, N0 P1 Kl, N1 P0 K1, N2 P1 K0, N2 P1 K1, N1 P2 K1, and N1 P1 K2, where the figures 0, 1, and 2 denote the relative proportion of a given element. The nutrients were given as follows: N = 35 grams of ammonium nitrate per pot loaded with 120 pounds of washed sand; P1 = 35 grams of monocalcium phosphate; Kl = 28 grams of sulfate of potash. Besides those fertilizers, each pot received 26 grams of magnesium sulfate and weekly doses of micronutrients as indicated by HOAGLAND and ARNON (1939). To apply the macronutrients the total doses were divided in three parts evenly distributed during the life cycle of cassava.
2. As far yield of roots and foliage are concerned, there are a few points to be considered:
2.1. the most striking effect on yield was verified when P was omitted from the fertilization; this treatment gave the poorest yields of the whole experiment; the need of that element for the phosphorylation of the starchy reserves explains such result;
2.2. phosphorus and nitrogen, under the experimental conditions, showed to be the most important nutrients for cassava; the effect of potassium in the weight of the roots produced was much less marked; it is noteworthy to mention, that in absence of potassium, the roots yield decreased whereas the foliage increased; as potassium is essential for the translocation of carbohydrates it is reasonable to admit that sugars produced in the leaves instead of going down and accumulate as starch in the roots were consumed in the production of more green matter.
3. Chemical analyses of roots revealed the following interesting points:
3.1. the lack of phosphorus brought about the most drastic reduction in the starch content of the roots; while the treatment N1 P1 K1 gave 32 per cent of starch, with NI PO Kl the amount found was 25 per cent; this result can be explained by the requirement of P for the enzymatic synthesis of starch; it has to be mentioned that the decrease in the starch content was associated with the remarkable drop in yield observed when P was omitted from the nutrient medium;
3.2. the double dosis of nitrogen in the treatment N2 P1 K1, gave the highest yields; however the increase in yield did not produce any industrial gain: whereas the treatment N1 P1 K1 gave 32 per cent of starch, by raising the N level to N2, the starch content fell to 24 per cent; now, considering the total amount of starch present in the roots, one can see, that the increase in roots yield did not compensate for the marked decrease in the starch content; that is, the amount of starch obtained with N1 P1 K1 does not differ statistically from the quantity obtained with N2 P1 K1; as far we know facts similar to this had been observed in sugar beets and sugar cane, as a result of the interaction between nitrogen and sugar produced; the biochemical aspect of the problem is very interesting: by raising the amount of assimilable nitrogen, instead of the carbohydrates polymerize to starch, they do combine to the amino groups to give proteinaceous materials; actually, it did happen that the protein content increased from 2.91 to 5.14 per cent.
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LITERATURA CITADA
- COWIE, G. A. 1951 Em "Potash", Edward Arnold and Co., London.
- EWERS, E. 1908 Uber polarimetrische starkebestimmung. Chemiker Zeit. 32: 996-997.
- GOMES, F. PIMENTEL e E. MALAVOLTA. 1949 Aspectos matemáticos e estatísticos da lei de Mitscherlich. An. E. S. A. "Luiz de Queiroz", U.S.P. 6: 193-229.
- GROSSMAN, J. 1946 A cultura da mandioca no Rio Grande do Sul. Rev. Fac. Agron. (Montevideo) 42: 1-33.
- HOAGLAND, D. R. and D. I. ARNON. 1939 The water culture method for growing plants without soil. Univ. of California Agr. Expt. Sta. (Berkeley, Calif.) Circ. 347.
- KJELDAHL, J. 1883 Neue Methode zur Bestimmung der Sticksfoffs in organischen Korpen. Z. anal. Chem. 22: 366-382.
- MALAVOLTA, K, T. COURY, E. A. GRANER, J. A. DE C. PACHECO, M. O. C. DO BRASIL SOBR. 1953 Adubação da mandioca (Manihot utilissima Pohl) I. Ensaio em areia lavada (Nota prévia). An. E. S. A. "Luiz de Queiroz", U.S.P.
- MEYER, B. S. and D. B. ANDERSON. 1944 Em "Plant Physiology", Fourth Printing, D. Van Nostrand Co., Inc., New York.
- NORMANHA, E. S. e A. S. PEREIRA. 1950 Aspectos agronômicos da cultura da mandioca (Manihot utilissima Pohl.) Bragantia 10: 179-202.
- RIECHELMANN. 1921 Zur Bestimmung der Starke in Manihotmehl. Zeitsc. f. offentliche Chem. 27: 5.
- WALTON, R. P. 1928 Em "A comprehensive survey of starch chemistry", vol. 1, The Chemical Catalog Co.
Estudos sôbre a alimentação mineral da mandioca (Manihot utilissima Pohl.)
Datas de Publicação
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Publicação nesta coleção
02 Out 2012 -
Data do Fascículo
1954
