Edivaldo Cia

Fitorreguladores de crescimento e capação na cultura algodoeira

Estudaram-se, em dez experimentos de campo, os efeitos dos seguintes fitorreguladores de crescimento e da capacao na cultura algodoeira: cloreto de clorocolina, aplicado na dose de 50 g/ha; cloreto de chlormequat, 100 g/ha e cloreto de mepiquat, 100 g/ha. A capacao foi realizada manualmente, planta por planta, na mesma epoca da aplicacao dos fitorreguladores, aos 60-70 dias da emergencia das plantas. O delineamento estatistico foi de blocos ao acaso, com cinco tratamentos e seis repeticoes e, a variedade utilizada, a IAC 19. Para a avaliacao dos resultados de producao e altura de plantas, efetuaram-se dois agrupamentos de ensaios, sendo um com maior e outro com menor desenvolvimento, ou seja: plantas em parcelas testemunhas com altura superior e inferior a 100 cm respectivamente. As demais caracteristicas agronomicas e tecnologicas da fibra foram analisadas em um so grupo. Para o grupo de plantas com maior desenvolvimento, foi obtido, em media, um aumento de 16,3 e 8,4%, respectivamente, para o tratamento com capacao e aplicacao de fitorreguladores. O fitorregulador proporcionou, em media, reducao de 12,1% na altura das plantas e a capacao, em media, 20,8%. Os fitorreguladores, indistintamente, proporcionaram aumento de peso do tapulho e das sementes, enquanto, com a pratica da capacao, nao se verificou esse efeito. A aplicacao de cloreto de clorocolina resultou em menor porcentagem de fibra do que o cloreto de mepiquat.

Efeitos da densidade de plantio e da aplicação de CCC, em algodoeiro

Excessive growth of the cotton plants Gossypium hirsutum L. in some regions causes laying and deficient luminosity, and a consequent lowering in yield and type of cotton. Such problems are specially serious in the case of mechanical picking where between-row spacing is fixed at about 40 inches. Combined effects of the use of growth limitant chemical CCC (Chlorocholine Chloride) and population density were studied in 1972/73 and 1975/76 in four localities of the State of Sao Paulo. Near Campinas and Sumare, the effects of 4, 8 and 16 plants/meter (respectively 40,000, 80,000 and 160,000 plants/ha) with and without CCC were studied. At Tiete and Piracicaba, 4, 8, 16 and 32 plants/meter were used (respectively 40,000, 80,000, 160,000 and 320,000 plants/ha). Only the treatments of 16 and 32 plants/meter were combined with CCC application. The concentration of CCC used was of 50 g a.i../ha applied from 50 to 70 days after emergence of the plants. The results showed that CCC limited the growth of plants, increased earliness of yield, decreased lint percentage and increased fiber length, boll and seed weight. There was no effect observed on cotton yield, fiber length uniformity, Micronaire, Pressely and fiber maturity. Higher density resulted in higher yield. High density also caused better length of fiber and lower boll weight.

Estudo do parcelamento da adubação potássica do algodoeiro

The advantage of split application of potassium chloride in cotton was studied in ten field experiments, conducted at different localities during the period of 1975 to 1981. In such cases, doses of 0, 60 and 120kg/ha of K2O, were placed in a fillet beside and below the seeds, at planting. In other treatments 1/3. 1/2, 2/3 or the total quantity of the highest level of potassium fertilizer was applied together with nitrogen, just after thinning, in a side-dressing operation, and covered slightly by subsequent cultivation. When all the K was applied at planting, linear effect on cotton yield appeared only in 10% of the experiments. This proportion increases to 40% when split applications were made. However, in combined analysis of all tests no significant difference was found between the two methods. Based in a study of simple correlations between cotton productivity and potassium application, expressed as the control treatments relative yield and indices of soil analysis ike 1/K+ and (Ca2+ + Mg2+)/K+, three groups of experiments were established, according to different expected responses. Considering the group of high expected responses [K 43], parcelled application resulted in increases of cotton yield when compared with the normal method of application. Similar tendency was observed in the group of intermediate expected responses [0.8-0.24 meq of K+ and 20-43 of (Ca2+ + Mg2+)/K+]. In potassium deficient soils split application of potassium chloride can be recommended, 1/2 or 2/3 of the total level furnished at planting and the remainder just after thinning, by side-dressing, mixed with nitrogenous fertilizer and followed by cultivation.

Reação de genótipos de algodoeiro à mancha de Ramularia em diferentes épocas e ambientes

Cotton genotypes, comprising cultivars and advanced lineages, were evaluated for their reaction to areolate mildew (Ramularia areola) in field experiments under natural infestation, at 60, 90 and 110 days after plant emergence in Ituverava-SP, and at 75, 100 and 120 days in Primavera do Leste-MT. In both localities, the latest evaluation was fundamental to adequately discriminate the genotypes and determine their effective degree of resistance to the pathogen. The earliest evaluations were inefficacious for this or underestimated the susceptibility of some genotypes. Highly significant genotype x environment interaction and extremely low, non-significant correlation between the mean scores of genotypes in the two experiments expressed contradictory performance of some genotypes, according to the locality, indicating possible existence of genetic variability of this pathogen in Brazil.

Efeitos da aplicação de N e de K sobre características gerais do algodoeiro cultivado em latossolos não deficientes em potássio

Em latossolos do Estado de Sao Paulo, nao deficientes em potassio para a cultura algodoeira, os efeitos de N e de K sobre certas caracteristicas da planta se relacionaram com os resultados da analise quimica do solo. A adubacao potassica diminuiu a precocidade da planta, em particular nos solos medianamente bem supridos em potassio. Tal indice nao foi afetado pela adubacao nitrogenada. A aplicacao de N aumentou os valores medios de peso de 100 sementes, peso de um capulho e indice de fibra, com destaque nos solos mais ricos em K. A adubacao potassica nao influenciou essas caracteristicas. O comprimento e a resistencia da fibra foram melhorados pela adubacao nitrogenada, no grupo de solos mais ricos em K. A aplicacao de K nao alterou significativamente as caracteristicas tecnologicas da fibra.

Estabilidade fenotípica, um complemento relevante na avaliação e classificação de genótipos de algodoeiro para resistência a doenças

ABSTRACT A manifestacao de doencas no algodoeiro depende, essencialmente,da patogenicidade do agente causal, do grau de resistencia do hospedeiroe das condicoes ambientais em que ocorre o evento. Este ultimo fator,por envolver circunstâncias que favorecem, ou nao, a infeccao e odesenvolvimento do patogeno, pode constituir causa de ineficienciana avaliacao de genotipos, levando a superestimacao de sua resistenciae em consequencia, a imprevisao de possiveis desempenhosinsatisfatorios, como ja se verificou, no caso de ramulose (6). Nessascondicoes, a consideracao da interacao genotipos x ambientes, em queestes ultimos representem situacoes diferenciadas com respeito aintensidade media de incidencia do patogeno, poderia constituir fatordecisivo na avaliacao e classificacao seguras da resistencia ou tolerânciagenetica a doencas. Este trabalho teve por objetivo confirmar taissuposicoes, mediante estudo da estabilidade fenotipica da resistenciaa diversas doencas, em alguns genotipos de algodoeiro disponiveis noBrasil.

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.

Comportamento das variedades de algodoeiro IAC 13-1, IAC 16 e IAC 17 em ensaio permanente de adubação com superfosfato simples

The Sao Paulo cotton varieties IAC 13-1, IAC 16 and IAC 17 were studied in a permanent field trial on a Latosolic B Terra Roxa soil, of low fertility, during the years of 1974/75, 1975/76 and 1976/77. They received different levels of simple superphosphate, namely 0, 225, 450 and 675kg/ha. The experimental design was a split plot, with four replications, containing superphosphate fertilizations on the main plots and varieties on split plots. Lime was applied before the first year of cropping and annual applications of 50kg/ha of N and 75kg/ha of K2O were made, on all plots. After three years of fertilization a soil analysis showed increases in phosphorus and calcium levels. The leaf blade calcium concentration was significantly increased by the use of superphosphate, while potassium concentration was decreased. Phosphorus and magnesium levels were also favorably influenced. The potassium content appeared to be negatively correlated with calcium and magnesium. The concentrations of N, S, P, Ca and K in the IAC 17 leaf blade were higher than those observed for IAC 13-1 and IAC 16. In the first year cropping a negative net income was observed, due to low responses to fertilization and to unfavorable cotton price. Because of the high levels of net, income obtained in the second and third year, it seems that, for future studies, the use of higher amounts of superphosphate, and new application methods need to be recommended. IAC 17 cotton showed through the years the highest capacity of utilization of simple superphosphate.

Effect of weed competition on cotton

The effect of weed competition on cotton (Gossypium hirsutum L.) was evaluated in the Centro Experimental de Campinas and the Estacao Experimental de Tiete during the 1970/71, 1971/72 and 1972/73 agricultural seasons. In the first season, competition periods of 10, 20, 30, 40, 60, 90 or 120 days, after emergence were studied, compared to checks always either with or without weeds. In the next seasons, competition was studied during the first 10, 20, 30 or 40 days after emergence, or after these periods, until harvest, maintained previously weed free for these different periods and afterwards competition was allowed until harvest. The experimental plots had four rows of five meters, distributed in randomized blocks with five or six replications. For evaluation of the competition effects the following parameters were considered: number, fresh and dry weights of weeds, after each competition period; fiber percentage, boll and seed weight, cotton yield, fiber length uniformity, Micronaire, Pressley and maturity, at harvest. The results showed a lower yield of cotton when the competition period was longer than 20 days after emergence. When the crop was maintained weed free for the first 30 to 40 days yield was similar to the completely weed free treatment. Competition periods of 90 days or longer determined negative effect on yield. In some cases a negative effect of weed competition was observed on fiber percentage, boll and seed weight, Micronaire, fiber uniformity and Pressley.

Germinação de sementes de algodoeiro deslintadas por diferentes métodos

Sementes de algodao do cultivar IAC 13-1 foram deslintadas por quatro diferentes metodos, a saber: mecanicamente, por acido sulfurico, por gas cloridrico e por flambagem. Apos selecao em mesa de gravidade, cada porcao relativa a um determinado metodo de deslintamento foi dividida em duas, sendo uma delas tratada com fungicida PCNB 75%, nas dosagens recomendadas pelos fabricantes. Apos o teste inicial de germinacao, as sementes foram armazenadas em ambiente de laboratorio e novos testes de germinacao foram feitos aos 3, 6 e 12 meses. Em todos os periodos de armazenamento as porcentagens de germinacao das sementes deslintadas por acido sulfurico e gas cloridrico foram superiores as das sementes deslintadas mecanicamente ou por flambagem que, por sua vez, foram iguais entre si ou com a flambagem ocupando posicao intermediaria. Em todos os periodos as porcentagens de germinacao das sementes tratadas com fungicida foram superiores as das sementes sem esse tratamento.