Luiz Alberto Staut

LEGUMES AND FORAGE SPECIES SOLE OR INTERCROPPED WITH CORN IN SOYBEAN-CORN SUCCESSION IN MIDWESTERN BRAZIL

The feasibility of no-tillage in the Cerrado (Savanna-like vegetation of Brazil) depends on the production of sufficient above-ground crop residue, which can be increased by corn-forage intercropping. This study evaluated how above-ground crop residue production and yields of soybean and late-season corn in a soybean-corn rotation were influenced by the following crops in the year before soybean: corn (Zea mays L.) intercropped with Brachiaria (Urochloa) brizantha cv. Marandu, B. decumbens cv. Basilisk, B. ruziziensis, cv. comum., Panicummaximum cv. Tanzânia, sunn hemp (Crotalaria juncea L.), pigeon pea [Cajanus cajan (L.) Millsp]; sole corn, forage sorghum [Sorghum bicolor (L.) Moench (cv. Santa Elisa)], and ruzi grass. In March 2005, corn and forage species were planted in alternate rows spaced 0.90 m apart, and sole forage species were planted in rows spaced 0.45 m apart. In October 2005, the forages were killed with glyphosate and soybean was planted. After the soybean harvest in March 2006, sole late-season corn was planted in the entire experimental area. Corn grain and stover yields were unaffected by intercropping. Above-ground crop residue was greater when corn was intercropped with Tanzania grass (10.7 Mg ha-1), Marandu (10.1 Mg ha-1), and Ruzi Grass (9.8 Mg ha-1) than when corn was not intercropped (4.0 Mg ha-1). The intercropped treatments increased the percentage of soil surface covered with crop residue. Soybean and corn grain yields were higher after sole ruzi grass and intercropped ruzi grass than after other crops. The intercropping corn with Brachiaria spp. and corn with Panicum spp. increases above-ground crop residue production and maintains nutrients in the soil without reducing late-season corn yield and the viability of no-till in the midwestern region of Brazil.

Faixas de suficiência para teores foliares de nutrientes em algodão e em soja, definidas em função de índices DRIS

A diagnose dos estados nutricionais do algodoeiro e da soja, pelo metodo de niveis criticos, tem-se embasado em faixas de suficiencia estabelecidas ha muitos anos, com pequenas adequacoes no periodo. Contudo, considerando-se que os teores foliares podem variar, dentre outros fatores, em funcao do tipo de amostra coletada e do potencial produtivo da cultura, torna-se importante a definicao de valores de referencia regionais. Este trabalho teve como objetivo estabelecer os teores adequados de nutrientes para algodoeiro e soja, por meio do ajuste de modelos de regressao para o teor foliar em funcao do indice de equilibrio nutricional definido pelo Sistema Integrado de Diagnose e Recomendacao (DRIS). Utilizou-se um banco de dados, constituido das produtividades e dos teores de nutrientes em amostras foliares de ambas as especies, coletadas em talhoes de lavouras comerciais e em parcelas experimentais, em Mato Grosso do Sul e Mato Grosso. Foram obtidas faixas de suficiencia para as folhas indice de algodoeiro (quinta folha totalmente formada, a partir do apice) e de soja (terceiro trifolio sem e com peciolo), com amplitude menor do que aquela estabelecida na literatura para estas culturas. Especificamente, para a soja, confirmou-se a existencia de diferencas nos valores de referencia em funcao do tipo de folha indice amostrado. Amostras de folha indice sem peciolo produzem teores significativamente maiores de N, P, B, Fe, Mn e Zn e menores de K, em relacao aos das amostras com peciolo. A desconsideracao do modo de amostragem pode induzir a falsos diagnosticos de deficiencias ou excessos nutricionais. Palavras-chave: analise foliar, sistema integrado de diagnose e recomendacao, folha indice, Glycine max, Gossypium hirsutum.

Efeitos do fósforo e potássio no rendimento e em outras características agronômicas do algodoeiro herbáceo

Com o objetivo de estudar o efeito da utilizacao de doses de fosforo e de potassio no rendimento e nas caracteristicas agronomicas do algodoeiro (Gossypium hirsutum L.), cv. IAC 20, foi conduzido um experimento em 1994/95, num Latossolo Vermelho-Escuro do Campo Experimental da Embrapa-Centro de Pesquisa Agropecuaria do Oeste (CPAO), em Ponta Pora, MS. O delineamento experimental foi o de blocos ao acaso, num esquema fatorial 3 x 5, com quatro repeticoes. As doses foram de 30, 60 e 90 kg ha-1 de P2O5, na forma de superfosfato triplo; 0, 30, 60, 90 e 120 kg ha-1 de K2O, na forma de KCl. Somente as doses de K2O influenciaram significativamente o rendimento de algodao em caroco, a altura da planta e o peso de 100 sementes e dos capulhos.

Crescimento de crambe na presença ou ausência de competição interespecífica

Crambe (Crambe abyssinica) has a cropping cycle of around 90 days, being suitable as an alternative to the second grain crop planted after soybean is harvested in the Center West region of Brazil. It is necessary to understand the growth and development dynamics of crambe plants in order to allow correct management of the production factors. This study aimed to describe the growth and development parameters of crambe plants under presence or absence of interspecific competition. The experiment was installed in the fall-winter 2011 in an Oxisoil, in completely randomized blocks design with three replications. Treatments comprised crambe plants growing either in presence or absence of interspecific simulated competition, throughout the cropping cycle. Plants were collected for the growth analysis every 15 days from harvest until 75 days after emergence. Growth parameters leaf area (AF), dry mass of stems/culms (MSC), leaves (MSF) and total (MST) dry mass, leaf area index (IAF), absolute (TCA) and relative (TCR) growth rates, net assimilation rate (TAL), specific leaf area (AFE), leaf area duration (DAF), leaf area ratio (RAF) and leaf mass ratio (RMF) were determined for the crop plants, submitted or not to competition, as well as for the simulated competitor. Crambe is a low competitive crop, being the competition more severe until 60-70 days after emergence. Besides, crop performance under field conditions was properly described by the net assimilation rate (TAL), which is also affected by the leaf area duration (DAF) and leaf mass ratio (RMF).

Occurrence of weed species in Jatropha curcas intercropping systems

This study aimed to evaluate the level of infestation by weed species in a consolidated Jatropha plantation, as a function of the plant species grown in interrows. The experiment was installed in 2006 at the district of Itahum, city of Dourados, state of Mato Grosso do Sul, Brazil, made possible through a partnership between Embrapa Western Agriculture and Paraiso Farm. Treatments consisted of (1) Jatropha in monocrop, with no plant at the interrrows; or the following plants cultivaded at the interrows of Jatropha: (2) Stylosanthes spp.; (3) Brachiaria ruziziensis; (4) Brachiaria ruziziensis + Stylosanthess pp.; (5) Brachiaria humidicola; (6) Panicum maximum cv. massai; (7) Cajanus cajan cv. anao; (8) Crotalaria spectabilis; (9) Crop rotation system 1 - (maize second crop -Crambe abyssinica - soybean - peanut); and (10) Crop rotation system 2 - (cowpea - radish - maize - cowpea) conducted for two years. Phytosociological characterization of weed species was accomplished in 2011 based on the Ecological Approach. Estimations of relative abundance, frequency, dominance and Importance Value Index were obtained. Areas were also characterized by the diversity coefficients of Simpson and modified Shannon-Weiner, and then grouped by cluster analysis. Areas with low soil coverage resulted in higher infestation levels; crop rotation in the interrows of Jatropha produced a significant reduction in weed infestation, but the lowest infestation levels were observed when grasses were grown intercropped with Jatropha. Lower diversity coefficients were associated with occurrence of the most troublesome weed species. In the first years after planting Jatropha, species of Brachiaria or a crop rotation involving species with high mulching ability and whose biomass exhibit a high C:N ratio, should be established in the interrows to avoid problems with weeds infestation.