adubação do algodoeiro: v - ensaios com azôto, fósforo e potássio, em "campos de cooperação" fertilizer experiments with cotton: v- experiments on the effect of n, p and k in private farms
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ID: 170110
1958
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Abstract
Neste artigo são apresentados os resultados obtidos em 71 ensaios de adubação do algodoeiro, conduzidos nos anos agrícolas de 1935-36 a 1941-42, em fazendas particulares ("campos de cooperação") localizadas em 34 municípios, compreendendo os principais tipos de solo do Planalto Paulista. Esses ensaios permitem comparar: a) o efeito de doses crescentes de azôto, fósforo ou potássio, sendo cada um desses nutrientes estudado na presença das doses maiores dos outros dois; b) o efeito do fósforo na ausência ou presença de azôto mais potássio, o do azôto na ausência ou presença do potássio (fósforo sempre presente) e o do potássio na ausência ou presença do azôto (fósforo sempre presente), e c) o efeito de três formas de fósforo (superfosfato, Renânia-fosfato e farinha de ossos degelatinados) na presença das doses maiores de azôto e potássio. De fósforo usaram-se sempre 40 e 80 kg/ha de P2O5; de azôto, 15 e 30 kg/ha de N até 1939-40 e 7,5 e 15 kg/ha em 1940-41 e 1941-42; de potássio, 40 e 80 kg/ha de K2O até 1939-40 e 25 e 50 kg/ha nos dois últimos anos. O azôto e o potássio foram sempre empregados nas formas de salitre do Chile e cloreto de potássio. Quanto ao fósforo, para estudar os efeitos citados em a e b se usou Renânia-fosfato em 1937-38 e 1938-39 e superfosfato nos outros anos; para o citado em c, as formas já mencionadas. Êsses adubos foram sempre aplicados conforme o método arraigado em nosso meio, nos sulcos de plantio, ao ser êste efetuado. O nutriente que regulou a produção foi, em regra, o fósforo. Os aumentos que êle provocou foram geralmente consideráveis, de modo que, a despeito de vários resultados nulos ou negativos, seu efeito médio foi satisfatório; contudo, o da dose maior foi pouco superior ao da menor. O superfosfato se mostrou superior à farinha de ossos e ao Renânia-fosfato, que deram praticamente o mesmo resultado. As respostas ao azôto e ao potássio, conquanto satisfatórias em cerca de um terço dos ensaios, foram nulas ou negativas na maioria deles, e suas doses maiores deram, em regra, resultados inferiores aos das menores. O efeito do fósforo foi praticamente o mesmo quando empregado sozinho ou na presença de azôto mais potássio; o do azôto, muito maior na ausência que na presença do potássio; o deste nutriente, muito maior na ausência que na presença do azôto. Muitos dos solos estudados estavam bem providos de azôto e potássio; por outro lado o uso de espaçamentos execessivamente largos deve ter diminuído a necessidade de adubações azotadas e potássicos. A aplicação do salitre por ocasião do plantio, e seu conseqüente arrastamento antes de as plantas o terem podido aproveitar, também deve ter influído para que, em muitos casos, o azôto não tenha obtido resposta satisfatória. Sem dúvida esses fatores concorreram para diminuir o efeito do azôto e do potássio, mas não justificam que, empregados em doses moderadas, eles tenham deprimido tão freqüentemente a produção. Em grande número de ensaios, tanto o azôto como o potássio e mesmo o fósforo (especialmente quando usado na forma de Renânia-fosfato) reduziram apreciàvelmente o "stand", e tais reduções foram mais intensas e freqüentes quando se empregaram as doses maiores do mesmo nutriente ou quando a um deles se adicionou outro. Essa foi a causa principal das depressões na produção e do incomum comportamento dos nutrientes na presença uns dos outros. As reduções no "stand" são atribuídas à excessiva concentração de sais no pequeno volume de terra que envolve as sementes, em conseqüência da aplicação dos adubos nos sulcos de plantio. Daí a conclusão de que, para poder avaliar com segurança o efeito dos adubos, estes devem ser aplicados por método mais eficiente que o arraigado em nosso meio.
This paper reports the results obtained in 71 fertilizer experiments with cotton conducted from 1935-36 up to 1941-42 in private farms located on the principal soil types of the State of São Paulo's cotton belt. In this work were compared 0, 40 and 80 kilograms of P2O5, per hectare, as well as three levels of nitrogen and of potash, and three forms of phosphates. Nitrogen and potash were used respectively as Chilean nitrate and potassium chloride; phosphorus, as superphosphate, Rhenaniaphosphate or bone meal. All the fertilizers were added, as usual, to the furrows and slightly mixed with the soil just before sowing. As a rule phosphorus increased considerably the yields, so that in spite of some poor results the average effect was satisfactory. However, the response to the higher rate of application was only slightly higher than that of the lower. Superphosphate was superior to both Rhenaniaphosphate and bone meal, which gave practically equal results. Nitrogen and potash, although giving good results in about one third of the experiments, did not increase the yield or even depressed it in most of them, and their higher levels generally gave poorer results than the lower. Some of the soils were apparently well supplied with nitrogen and potash, and the excessive spacing then used no doubt contributed to lessen the need for nitrogenous and potassic fertilizers. The application of nitrogen at planting time and the consequent loss through leaching before the cotton plants could take it up, may also have contributed to many small responses to that nutrient. These factors do not explain, however, why moderate doses of nitrogen and potash so often depressed the yields. Nitrogen, potash and even phosphorus (chiefly when used as Rhenaniaphosphate) reduced the stands in many experiments, and these reduction were the principal causes of the negative effects in the yields. As the reductions of the stands were atributed to the application of the fertilizers in contact with the seed, it was concluded that, for evaluating their effect they must be applied by other method more efficient than that used in the experiments.
This paper reports the results obtained in 71 fertilizer experiments with cotton conducted from 1935-36 up to 1941-42 in private farms located on the principal soil types of the State of São Paulo's cotton belt. In this work were compared 0, 40 and 80 kilograms of P2O5, per hectare, as well as three levels of nitrogen and of potash, and three forms of phosphates. Nitrogen and potash were used respectively as Chilean nitrate and potassium chloride; phosphorus, as superphosphate, Rhenaniaphosphate or bone meal. All the fertilizers were added, as usual, to the furrows and slightly mixed with the soil just before sowing. As a rule phosphorus increased considerably the yields, so that in spite of some poor results the average effect was satisfactory. However, the response to the higher rate of application was only slightly higher than that of the lower. Superphosphate was superior to both Rhenaniaphosphate and bone meal, which gave practically equal results. Nitrogen and potash, although giving good results in about one third of the experiments, did not increase the yield or even depressed it in most of them, and their higher levels generally gave poorer results than the lower. Some of the soils were apparently well supplied with nitrogen and potash, and the excessive spacing then used no doubt contributed to lessen the need for nitrogenous and potassic fertilizers. The application of nitrogen at planting time and the consequent loss through leaching before the cotton plants could take it up, may also have contributed to many small responses to that nutrient. These factors do not explain, however, why moderate doses of nitrogen and potash so often depressed the yields. Nitrogen, potash and even phosphorus (chiefly when used as Rhenaniaphosphate) reduced the stands in many experiments, and these reduction were the principal causes of the negative effects in the yields. As the reductions of the stands were atributed to the application of the fertilizers in contact with the seed, it was concluded that, for evaluating their effect they must be applied by other method more efficient than that used in the experiments.
| Reference Key |
schmidt1958bragantiaadubao
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| Authors | ;W. Schmidt;O. S. Neves;E. S. Freire |
| Journal | revista espanola de salud publica |
| Year | 1958 |
| DOI |
10.1590/S0006-87051958000100027
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