Carlos A. M. Ferraz

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.

Correlação entre o efeito da adubação potássica no algodoeiro e a análise química do solo

No estudo de 178 experimentos de adubacao do algodoeiro realizados em varios tipos de solo do Estado de Sao Paulo, no periodo de 1957-65, foi encontrada correlacao entre as respostas na producao, obtidas pela aplicacao de 60 kg/ha de K2O, e os resultados revelados pela analise quimica do solo. Uma regressao multipla de 1.° grau, descrevendo o efeito da adubacao potassica em funcao da relacao Ca++ /K+ e do teor de K+, elementos trocaveis no solo, revelou um coeficiente R = 0.804**, explicando cerca de 65% da variacao das respostas. Considerando as correlacoes simples lineares, a relacao Ca++/K + explicou 59% do efeito da adubacao, ao passo que a parte esclarecida pelo teor de K+, isoladamente, nao ultrapassou os 23%. Nenhum ganho apreciavel, em precisao, foi obtido pela introducao de uma funcao quadratica para descrever estas correlacoes.

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.

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.

Effects of planting density and growth regulator on cotton crop

The effects of population density (4, 8 and 16 plants/meter) and the use of chemical growth limitant chlorocholine chloride (CCC) were studied during four years (from 1976/77 to 1979/80), in three localities of Sao Paulo State, Brazil. The variety was IAC 18 and the inter-row spacing was 1.0 m. The CCC used was 50 g a.i./ha, applied from 60 to 70 days after the emergence of the plants. In the trials where plant height was higher than 140 cm, the yield was lower in the highest population density than in the others, and the growth limitant had positive effect in that treatment, promoting increase in the yield. When plants were shorter than 140 cm, no effects were observed in the yield to growth limitant. The CCC increased earliness of yield, number of bolls located in the plants below 35 cm, weight of 100 seeds, weight of one boll, fiber length, maturity and tenacity. It also decreased number of bolls with abnormal opening and fiber percentage, and had no effect in Micronaire index and uniformity.

Estudo comparativo de métodos de deslintamento de sementes de algodoeiro

A comparative study of cotton seed delinting methods was carried out during the years of 1973/74 to 1975/76, in the State of Sao Paulo, using the commercial variety IAC 13-1. Mechanical, acid, gas, and flame delinting were compared, with or without fungicide application. The percentages of seedlings obtained were computed. The best results corresponded to acid and gas delinting associated to treatment with fungicide. The lowest percentages were obtained with mechanical delinting. The best time for counting seedling stands showed to be from twelve to nineteen days afteremergence.

Resposta do algodoeiro à seleção para resistência à fusariose, em condições de campo

A process of continuous selection and testing for fusarium wilt resistance of cotton is described and its efficiency discussed. It essentially consists in individual selection, progeny tests, mass selection in the best progenies and testing of the corresponding MS in the third year. Individual selections may come from the breeding programs as well as from crop fields and artificial inoculation in green-houses. All the tests are made in field conditions. Data of 1969 to 1971, obtained in two cycles of selection, showed that the process described was efficient in increasing both tolerance and resistance to wilt. The increase was larger in the case of originally susceptible material than in that of resistant one. This difference was smaller in years of more intense wilt. Also the actual values of increases were smaller in such years. The results suggest that fusarium wilt resistance, in cotton, may be a matter of concentration of minor genes in the population, rather than of the presence of a few major genes.

Variabilidade de Xanthomonas malvacearum (E. F. Smith) Dowson, no estado de São Paulo

No presente trabalho foi determinada a variabilidade de X. malvacearum, em condicoes de casa de vegetacao, baseando-se na reacao dos hospedeiros diferenciais para racas fisiologicas do patogeno. A tecnica de inoculacao empregada foi a de riscos feitos na pagina inferior das folhas e para avaliacao dos sintomas foi adotada uma escala que variou de 1 a 5. Foi detectada a ocorrencia das racas fisiologicas 3, 8 e 10. A linhagem do algodoeiro IAC RM3-4133 71/523 foi resistente a raca fisiologica 3, enquanto que as linhagens (Acala x Nu.16) 71/213 e IAC 12-2 71/170 foram resistentes as racas 3, 8 e 10.

Improvement of the São Paulo cotton varieties: origin and breeding of the IAC 12 variety

A variedade paulista de algodoeiro IAC 12 resultou de um programa de cruzamento entre variedades comerciais do tipo Upland, que visou reunir varias propriedades economicamente vantajosas. Este programa foi iniciado no ano agricola de 1942/43 e terminou em 1959, quando as primeiras sacas de semente basica daquela variedade foram entregues a Secretaria da Agricultura, para multiplicacao em grande escala. Originaria de cruzamento entre linhagens das variedades comerciais Stoneville 2B e Delfos, ela veio resolver definitivamente a crise de comprimento da fibra que afligia a cotonicultura paulista, por volta de 1956, e contribuiu para melhorar o aspecto de campo e as demais qualidades agronomicas e tecnologicas das variedades paulistas. Neste trabalho sao relatadas as diversas fases da criacao da variedade IAC 12 assim como os processos envolvidos e os resultados alcancados.