Studies on plant growth are interesting because they provide explanations for the factors that influence yield in various crops. The objective of this work was to evaluate growth and yield in corn cultivar AG1051, when in competition with weeds. Cultivar AG 1051 was submitted to two groups of treatments: weed control, and sampling periods for dry biomass evaluation. The weed control treatments consisted of hoeing (two hoeings performed at 20 and 40 days after sowing) and no hoeing. Sampling periods consisted of collecting the above-ground part and roots of corn every fifteen days, until 105 days after sowing (DAS); the first sampling was performed 30 DAS. A completely randomized block design with ten replicates was used. For the characteristics evaluated in a single season, statistical analyses were carried out as a random block experiment. For the characteristics evaluated in several periods, statistical analyses were carried out as random blocks with split-plots (weed control assigned to plots). Fourteen weed species, unevenly distributed throughout the experimental area, were the most important. The growth observed for the above-ground part and root system of corn was 30% smaller in the non-hoed plots, compared to the hoed plots. Lack of weed control increased dry matter of the above-ground part of the weeds and reduced the number of unhusked and husked marketable green ears by 23% and 49%, respectively. Grain yield reduction caused by lack of weed control reached 38%.

Among Brazilian soils orders, there are some of it classified as acid soils, which need correction to guarantee crop productivity. Currently, limestone is the most used soil corrective and wood ash has been a sustainable alternative to this process. Thus, the objective was to evaluate the effect of two correctives of soil acidity on an Oxisol collected in the Brazilian Cerrado area using limestone and wood ash and the effect of soil correction on initial growth of cowpea. Two greenhouse experiments were carried out: 1) with limestone, using base saturation levels (V%) of 0, 20, 40, 60 and 80; and 2) wood ash, with doses of 0, 8, 16, 24 and 32 g•dm −3 , both in five randomized blocks. At 40 days after sowing, it was verified that pH values were within the range considered ideal for soil (pH of 5 to 7), according to the increase of base saturation levels and wood ash doses, but limestone provided faster results. Initial growth of cowpea was positively influenced by soil correction with use of both correctives. Wood ash and limestone increased soil pH to adequate values and resulted in better initial crop development.

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Alfalfa, considered one of the most important forage worldwide, requires a base saturation in the soil of approximately 80%, and this is a factor that can limit the expansion of cultivation of this crop in tropical soils that are predominantly acidic. The objective of this study was to evaluate the influence of base saturation levels on the development of alfalfa in soil of the Brazilian Cerrado. The experiment was conducted in the greenhouse, whose experimental units consisted of plastic pots with a capacity of 2 dm 3 . The experimental design was a completely randomized design with six treatments and five repetitions. The treatments consisted of six levels of base saturation (10,

RESUMOO uso econômico da água garantirá que políticas e práticas de irrigação sejam sustentáveis, para que no futuro um terço da alimentação mundial possa continuar a vir de 15% da superfície terrestre do planeta. Em algumas regiões do Brasil, existem inúmeras propriedades rurais que não possuem o fornecimento público de energia elétrica. Nesses locais, para que a agricultura irrigada moderna e automatizada possa ser introduzida é necessária a utilização de bombas e equipamentos que dispensam o emprego de energia elétrica. Diante deste cenário, idealizou-se um bombeamento da água de irrigação por um sistema de roda hidráulica associado à automação da irrigação por gotejamento a partir, apenas, de energia hidráulico-mecânica. Para isso utilizou-se o mesmo princípio do sistema de acionamento automático para aspersão em malha, desenvolvido por Grah (2011). O objetivo do presente trabalho foi demonstrar a viabilidade técnica de uma alternativa para o bombeamento de água para uma irrigação automatizada sem uso de energia elétrica. O equipamento de automação desenvolvido para aspersão em malha, também pode ser utilizado para sequenciar parcelas de irrigação localizada. Os resultados revelaram que o sequenciador automático é uma alternativa técnica viável, que pode ser aplicada em propriedades de pequeno e médio porte que não possuem disponibilidade de energia elétrica. Palavras ABSTRACTParsimonious use of water will ensure irrigation policies and practices are sustainable, so that into the future one third of the world's food can continue to come from just 15% of the earth's land area. In some regions of Brazil, there are many farms that have no public supply of