Cover crops on the development of beggar's-tick

Studies to identify potential cover crops species for the no-till system and minimal amounts of biomass required to reduce the emergence and development of weeds in cereal crop areas may represent an important tool in the integrated weed management. Thus, this study aimed at evaluating the inhibition of the emergence and growth of Bidens pilosa plants, using different cover crops biomass levels on the soil surface. The experiment was carried out in a greenhouse located in Bom Jesus, Piauí State, Brazil, from December 2011 to March 2012, in a randomized experimental blocks design with four replications, in a (5x6)+1 factorial scheme, consisting of six cover crop species and five biomass levels on the soil surface, plus a control with no soil cover. The species evaluated were Pennisetum glaucum (ADR 7010 and ADR 300 cultivars), Crotalaria ochroleuca, Urochloa ruziziensis (syn. Brachiaria ruziziensis), Crambe abyssinica and Fagopyrum tataricum, at five biomass levels corresponding to 4.0 t ha-1, 8.0 t ha-1, 12.0 t ha-1, 16.0 t ha-1 and 20.0 t ha-1. Urochloa ruziziensis and Fagopyrum tataricum were considered the best ones for controlling B. pilosa, with 4.0 t ha-1 of their biomass being sufficient to reduce the total number of emerged plants, germination speed index, shoot dry biomass, leaf area, root dry biomass and root volume of B. pilosa

Effect of water regimes and plant densities on cowpea production

Cowpea has been cultivated in a rudimentary form in the main producing regions of Brazil, resulting in lower grain yields, when compared to the crop potential. The use of technologies such as water regimes, adequate plant density and soil management are alternatives to increase this crop yield. This study aimed at evaluating the effects of different water regimes and plant densities on the yield components of cowpea cultivated under conventional and no-tillage systems. A randomized block design in a split-plot factorial, with four replications, was used. The treatments consisted of five water regimes in the plots (157.00 mm, 189.00 mm, 234.00 mm, 274.00 mm and 320.00 mm) and five plant densities as subplots (12 plants m-2, 16 plants m-2, 20 plants m-2, 24 plants m-2 and 28 plants m-2). The evaluated variables were: number of pods per plant, number of pods per area, pod length and grain yield. The combination between 270 mm of irrigation water depth with a density of 280,000 plants ha-1 resulted in higher grain yield using the no-tillage system, while the combination between the density of 280,000 plants ha-1 and 320 mm of water depth favored the highest grain yields in the conventional growing system

BIOMASS AND NUTRIENT CYCLING BY COVER CROPS IN BRAZILIAN CERRADO IN THE STATE OF PIAUI

Research on the performance of cover crops in crop systems of annual crops in the Brazilian state of Piauí contributes to increases in yield, greater efficiency of fertilizers and mitigation of environmental impacts. The aim of this study was to evaluate the performance of cover crops in terms of biomass production and the accumulation and release of nutrients during the crop season (November to April) in an oxisol in the Brazilian Cerrado in the state of Piauí that was submitted to different crop production systems including soybeans, maize and upland rice. The experiment was established during the 2010/11 and 2011/12 crop years in the rural area near the municipality of Bom Jesus, Piauí. The experimental design was a randomized block in a split-plot array. Different soil management systems (conventional and no-till) were evaluated in the main plots. Different crop production systems consisting of cover crops sown in the off-season (April to November), and annual crops sown during the crop season (November to April) were implemented in the subplots. The crop production systems that included Urochloa ruziziensis and Pennisetum glaucum overseeded on soybeans and Urochloa ruziziensis simultaneously intercropped with maize stood out in terms of biomass production and the accumulation and release of nutrients. Yields of maize and upland rice declined when sown under newly implemented no-till soil management. Keywords: Brachiaria. Millet. Crotalaria. No-till. Research on the performance of cover crops in crop systems of annual crops in the Brazilian state of Piauí contributes to increases in yield, greater efficiency of fertilizers and mitigation of environmental impacts. The aim of this study was to evaluate the performance of cover crops in terms of biomass production and the accumulation and release of nutrients during the crop season (November to April) in an oxisol in the Brazilian Cerrado in the state of Piauí that was submitted to different crop production systems including soybeans, maize and upland rice. The experiment was established during the 2010/11 and 2011/12 crop years in the rural area near the municipality of Bom Jesus, Piauí. The experimental design was a randomized block in a split-plot array. Different soil management systems (conventional and no-till) were evaluated in the main plots. Different crop production systems consisting of cover crops sown in the off-season (April to November), and annual crops sown during the crop season (November to April) were implemented in the subplots. The crop production systems that included Urochloa ruziziensis and Pennisetum glaucum overseeded on soybeans and Urochloa ruziziensis simultaneously intercropped with maize stood out in terms of biomass production and the accumulation and release of nutrients. Yields of maize and upland rice declined when sown under newly implemented no-till soil management

Doses e épocas de aplicação de potássio no desempenho agronômico do milho no cerrado piauiense

Since the ‘Cerrado’ area of Piaui State, Brazil is a relatively new agricultural frontier, there is lack of information regarding the handling of potassium fertilization, since no information about the better fertilization techniques for this area was provided by the federal research corporations. Thus, the aim of this study was to evaluate the effect of dose and time of application of K2O in corn grown in a ‘Cerrado’ area at the Paui state. The experiment was conducted in a yellow dystrophic oxisol with a completely randomized block design, with four repetitions in a (4x4)+1 factorial. The treatments consisted of combinations of four potassium levels: 30, 60, 90 and 120 kg ,K2O ha-1 + additional control (zero kg ha-1) applied in four seasons : 100% at sowing; 100% at 30 days after sowing (DAS); 50% at sowing and 50% 30 DAS; 50% 20 DAS and 50% at 40 DAS. Only the height, stem diameter and agronomic efficiency of the K use were influenced by the K+ time of application, especially with the application of 50% at sowing and 50% at 30 DAS. Except for the relative chlorophyll content and ear length, all other variables were influenced by K2O doses. The application of K2O resulted in greater increases of other evaluatedvariables, mainly for the yield obtained when the dose of 53 kg K2O ha-1 was used.Por se tratar de uma fronteira agrícola relativamente nova, o cerrado piauiense ainda necessita de informações quanto ao manejo de adubação potássica, uma vez que, ainda não há uma recomendação técnica de adubação para o milho por parte dos órgãos oficiais de pesquisa. Assim, objetivou-se com esse trabalho avaliar a eficiência de doses e épocas de aplicação de K2O na cultura do milho no cerrado piauiense. O trabalho foi conduzido a campo em LATOSSOLO AMARELO distrófico. O delineamento experimental utilizado foi blocos casualizados, com quatro repetições, em esquema fatorial (4x4)+1, sendo os tratamentos compostos pela combinação de quatro doses de potássio: 30, 60, 90 e 120 kg de K2O ha-1 + testemunha adicional (zero kg de K2O ha-1), aplicadas em quatro épocas: 100% na semeadura; 100% aos 30 dias após a semeadura (DAS); 50% na semeadura e 50% 30 DAS; 50% 20 DAS e 50% 40 DAS. Apenas a altura, o diâmetro caulinar e a eficiência agronômica no uso do K+ foram influenciados pelas épocas de aplicação de K+, com destaque positivo para a aplicação de 50% na semeadura e 50% aos 30 DAS. Com exceção do teor relativo de clorofila e comprimento da espiga, todas as demais variáveis foram influenciadas pelas doses de K2O. A aplicação de K2O proporcionou maiores incrementos nas demais variáveis, sendo a maior resposta para a produtividade de grãos obtida com 53 kg de K2O ha-1

Análise de trilha do rendimento de grãos de soja na microrregião do Alto Médio Gurguéia

The objective of this work was to evaluate, by using path analysis, the influence of some agronomic characters on soybean yield. An experiment was conducted in cerrado soil, in Serra do Quilombo, Bom Jesus, Southern of Piaui State, from december 2007 to april 2008, in an Oxisol. The experimental design was randomized blocks, with treatments consisting of six levels of phosphorus (0, 40, 60, 100, 120 and 140 kg P2O5 ha-1) with four replications. Some characteristics were evaluated: plant height, height of first pod insertion, number of nodes per plant, number of string beans per plant, 100 grains weight, dry weight and total grain production per plant. The number of pods per plant was the yield component that showed the greatest direct effect on dry matter and total grain production per plant. The number of nodes per plant had a strong indirect effect on dry matter production. The variable height of first pod insertion showed lower correlation with the other variables.Objetivou-se com este trabalho avaliar, através da análise de trilha, a influência de alguns caracteres agronômicos, sobre o rendimento de grãos de soja. Foi instalado um experimento em solo de cerrado na Serra do Quilombo, município de Bom Jesus, Sul do Estado do Piauí, no período de dezembro de 2007 a abril de 2008, em um Latossolo Amarelo. O delineamento experimental utilizado foi o de blocos casualizados, sendo os tratamentos constituídos por seis doses de fósforo (0; 40; 60; 100; 120 e 140 kg ha-1 de P2O5) com quatro repetições. Avaliou-se a altura de plantas, altura de inserção da primeira vagem, número de nós por planta, número de vagens por planta, peso de 100 grãos, peso de matéria seca e produção total de grãos por planta. O número de vagens por planta foi o componente de produção que apresentou maior efeito direto sobre a produção de matéria seca e total de grãos por planta. O número de nós por planta exerceu forte efeito indireto sobre a produção de matéria seca. A variável altura de inserção da primeira vagem apresentou menor correlação com as demais variáveis. Path analysis of soybean yield in the micro region of Alto Médio GurguéiaAbstractThe objective of this work was to evaluate, by using path analysis, the influence of some agronomiccharacters on soybean yield. An experiment was conducted in cerrado soil, in Serra do Quilombo,Bom Jesus, Southern of Piaui State, from december 2007 to april 2008, in an Oxisol. The experimentaldesign was randomized blocks, with treatments consisting of six levels of phosphorus (0, 40, 60, 100,120 and 140 kg P2O5 ha-1) with four replications. Some characteristics were evaluated: plant height,height of first pod insertion, number of nodes per plant, number of string beans per plant, 100 grainsweight, dry weight and total grain production per plant. The number of pods per plant was the yieldcomponent that showed the greatest direct effect on dry matter and total grain production perplant. The number of nodes per plant had a strong indirect effect on dry matter production. Thevariable height of first pod insertion showed lower correlation with the other variables.