Antonio Pereira de Camargo

A análise de solo para discriminar respostas à adubação para a cultura do milho

In this paper some of the criteria that have been used in the State of Sao Paulo in soil test interpretation were studied, correlating soil test parameters with corn response to applied nitrogen, phosphorus or potassium in 25 field experiments. Exchangeable potassium and phosphorus soluble in 0.05N H2SO, correlated well with responses of the crop to the applied nutrients. Nitrogen responses could not be correlated to soil test values. Response curves and fertilizer efficiencies are presented for nitrogen, phosphorus and potassium. For the two last nutrients, the average curves are given for very low, low, medium and high soil test values.

Exchangeable aluminum and base saturation as criteria for lime requirement

O criterio do aluminio para determinar a necessidade de calagem de solos, vem sendo usado ha dezesseis anos no Brasil. As quantidades de calcario indicadas sao em geral baixas. Neste trabalho, procurou-se avaliar esse metodo, com base em resultados de ensaios de calagem, realizados em tres locais e durante varios anos. Em Mococa, em podzolico vermelho-amarelo, foram considerados cinco plantios de milho, um de algodao e um de soja; em Sao Simao, em latossolo vermelho-escuro textura media, tres plantios de soja; em Guaira, em latossolo roxo, tres plantios de algodao. Em todos os casos, a producao continuava a aumentar, com a elevacao das doses de calcario, mesmo em niveis de calagem superiores aqueles suficientes para praticamente neutralizar o aluminio. Mostrou-se que o criterio do aluminio nao e adequado, do ponto de vista quantitativo, para calculos de calagem. O criterio da saturacao em bases apresentou-se como alternativa adequada, para esse fim, relacionando bem com as respostas das culturas, alem de ser muito flexivel, de facil utilizacao, e apresentar fundamento teorico adequado. Em geral, a producao maxima nao foi atingida nos ensaios, mas estimou-se que ela seria obtida com valores de saturacao em bases acima de 60%.

Adubação NK em três variedades de cana-de-açúcar em função de dois espaçamentos

Two factorial field experiments were carried out in the years of 1981 to 1984, in two soils (Dark-red Latosol - LE, and Dusky-red Latosol - LR) of the State of Sao Paulo, Brazil, with the objective of assessing the effect of N and K application on yield of three varieties of sugarcane grown in two row spacings. The fertilizer treatments for plant-cane consisted of the following combinations of N and K2O, in kg/ha: 0-210, 70-210, 140-210, 210-210, 140-0, 140-70, 140-140, and 140-210. All plots received equal amounts of P, at the rate of 120 kg P2O5/ha. The fertilizer treatments for 1st and 2nd ratoon were the same for all plots: 100, 30, and 120 kg/ha of N, P2O5, and K2O, respectively. Significant effects of row spacings, varieties, and NK application were observed on yields of cane and sucrose in both soils. Maximum calculated yields of cane were obtained with 165 kg N/ha and 148 kg K2O/ha in the LR soil, and 180 kg N/ha in the LE soil. The corresponding values for maximum sucrose yields were 153 kg N/ha and 104 kg K2O/ha in the LE soil and 128 kg K2O/ha in the LR soil. The highest rates of both N and K applied caused a decrease in the sucrose concentration of cane so that the rates of fertilizer application necessary for maximum sucrose yield were lower than those for maximum cane yield. The data for total cane and sucrose production (plant + ratoon) showed that the effects of N and K were similar to those obtained for plant-cane. The 1.2-meter row spacing produced higher yield of cane per unit area than that of the 1.5-meter spacing (increases of 14% in LR and 7% in LE, for plant + ratoon), and lower values per unit length of row (- 18% in LR and - 10% in LE). Varieties IAC58-480 and IAC64-257 showed greater sucrose yield than that of IAC52-150: 17% and 12% respectively in LR; in LE, both varieties produced 12% more than IAC52-150. Varieties also differed regarding sucrose content: IAC58-480 was 5% higher than IAC52-150 and the latter was 2% higher than IAC64-257.

Melhoramento do algodoeiro para resistência múltipla a doenças, nematóides e broca-da-raiz em condições de campo

Um modelo de selecao e teste de linhagens de algodoeiro para resistencia multipla a doencas e pragas, adotado pelos melhoristas da Secao de Algodao do Instituto Agronomico, e descrito e discutido com base nos dados obtidos no periodo de 1981 a 1991. Condideraram-se as murchas de Fusarium e de Verticillium, a ramulose, a mancha angular, os nematoides e a broca-da-raiz como fatores adversos. Foram sugeridos indices relativos de resistencia apropriados a cada fator e um indice de resistencia multipla para a avaliacao global dos resultados. Discutem-se as evolucoes desses indices durante o periodo, assim como as correlacoes observadas anualmente entre os indices. Houve, no periodo, tendencia para nivel crescente de resistencia para todos os fatores, com excecao da ramulose, cujo indice medio de resistencia oscilou ao redor de 70% da testemunha resistente, no conjunto das linhagens promissoras obtidas anualmente. As correlacoes entre os indices de resistencia aos fatores variaram ao redor de zero, de maneira casual de ano para ano, atingindo raras vezes o nivel de significância de 5%. Apareceram correlacoes negativas significativas, no final do periodo, entre ramulose, de um lado, e Verticillium e mancha angular do outro, cuja importância e consequencia sao discutidas. O indice medio de resistencia multipla cresceu de 56,7% no periodo, chegando a 0,776 no final, sendo que o valor 1,000 representaria a reuniao de todos os genes disponiveis de resistencia numa mesma linhagem.

Melhoramento genético da cana-de-açúcar: VI. Ensaios de clones provenientes de hibridações realizadas em 1974, 1977, 1978 e 1979, avaliados na Região de Piracicaba (SP)

Sugarcane clones obtained in crosses made in 1974, 1977, 1978 and 1979, were tested in two locations in the Piracicaba region. The clones and commercial varieties SP70-1143, IAC64-257, NA56-79 and CB41-76 were evaluated for agricultural and industrial traits in an average of three harvests. The clone IAC78-23 was obtained for cultivation in the region with high cane and sugar yields and adequate for use in middle and late harvest, and the IAC79-1011 with medium yield and high sugar content, indicated for inicial harvest. The clones IAC77-186, IAC78-54, IAC78-90 and IAC79-1149 showed medium yield and high sugar content, indicated for middle harvest in soils with high fertility.

Comportamento de variedades de cana-de-açúcar no plantio de setembro-outubro na região de Piracicaba (SP)

An experiment was conducted from 1976 to 1979, in Latosolic B terra roxa, at the Sugarcane Experimental Station in Piracicaba, State of Sao Paulo, Brazil, to evaluate the production in September-October planting of some sugarcane varieties grown in the State of Sao Paulo. Analysing the results, it was observed, by comparison of the sugarcane production (t/ha) and sugar content (kg/t of cane) that the best varieties for planting in September-October, in Piracicaba region are NA56-79, CB47-89, IAC52-150 and Co740.

Tentativa de infestação artificial do solo com Fusarium oxysporum f. sp. vasinfectum em condições de campo

In order to establish an experimental breeding field for Fusarium wilt resistance, in cotton, an area of about 8,000m2 was artificially inoculated with the pathogen twice during the crop season. A total of 14 inoculations was performed along the 7 consecutive years of experimentation. However, taking into account the typical external and internal symptoms exhibited by the plants, the incidence of the diseases was considered low and unsatisfactory, as the final purposes are concerned. The possible causes of the unsuccess, such as climatic conditions, soil texture, method of inoculation, supressiveness of the soil to Fusarium and absence of Fusarium x nematodes interaction, are discussed.