No abstract

The forthcoming of silicon (Si) highly soluble sources provided a suitable alternative to Si use in agroecosystems. There are many benefits associated to Si application in crops, such as improvement in feed quality. In this sense, the aim of this work was to evaluate the effect of Si foliar application on physiological quality, biomass production, and silicon accumulation in Sorghum bicolor. The experiment was conducted under greenhouse condition using an entirely randomized design, with five Si rates (0 as control), 0.84, 1.68, 2.52, and 3.36g L -1 of Si) applied as potassium and sodium silicate, with four repetitions. In each treatment, applied solutions were balanced in potassium in order to isolate the Si effect. The following measurements were taken: growth, biomass production, Si accumulation, and physiological quality. Supplying Si via leaves did not affect the sorghum growth rate and the relative chlorophyll index; however, leaf area increased 23% with the use of 2.36 g L -1 of Si. Physiological variables are influenced by increasing Si rates, with rates close to 1.68 g L -1 of Si causing the best photosynthetic rates and stomatal conductance. The use of potassium silicate as a source of silicon is an alternative for productivity increases up to 30%, but an economic study on the viability of its commercial application in the production chain of Sorghum bicolor is necessary.

Purpose The mineralization/immobilization of nutrients from the crop residues is correlated with the quality of the plant material and carbon compartments in the recalcitrant and labile soil fractions. The objective of this study was to correlate the quality and quantity of crop residues incubated in the soil with carbon compartments and CO 2 -C emission, using multivariate analysis. Materials and methods The experiment was conducted in factorial 4 + 2 + 5 with three replicates, referring to three types of residues (control, sugarcane, Brachiaria, and soybean), and two contributions of the crop residues in constant rate, CR (10 Mg ha −1 residue), and agronomic rate, AR (20, 8, and 5 Mg ha −1 residue, respectively, for sugarcane, soybean, and Brachiaria), evaluated five times (1, 3, 6, 12, and 48 days after incubation). At each time, we determined the CO 2 -C emission, nitrogen and organic carbon in the soil, and the residues. In addition, the microbial biomass and water-soluble, labile, and humic substance carbons fractionated into fulvic acids, humic acids and humin were quantified.Results and discussion Higher CO 2 -C emissions occurred in the soil with added residue ranging from 0.5 to 1.1 g CO 2 -C m −2 h −1 in the first 6 days of incubation, and there was a positive correlation with the less labile organic soil fractions as well as residue type. In the final period, after 12 days of soil incubation, there was a higher relation of CO 2 -C emission with carbon humin. The sugarcane and soybean residue (20 Mg ha −1 ) promoted higher CO 2 -C emission and the reduction of carbon residue. The addition of residue contributed to an 82.32 % increase in the emission of CO 2 -C, being more significant in the residue with higher nitrogen availability. Conclusions This study shows that the quality and quantity of residue added to soil affects the carbon sequestration and CO 2 -C emission. In the first 6 days of incubation, there was a higher CO 2 -C emission ratio which correlates with the less stable soil carbon compartments as well as residue. In the final period of incubation, there is no effect of quality and quantity of residue added to soil on the CO 2 -C emission.

The objective of this study is to evaluate the effects of sources and doses of boron on the physiological quality and production yield of Phaseolus vulgaris grown using a central pivot irrigated system on a tropical climate region. The experiment was a 4x5 factorial design representing four sources of boron (boric acid, borax, borogran and FTE BR 12) and five boron doses (0, 1, 2, 3 and 4 kg ha -1 ), with four replications. The following parameters were measured: relative chlorophyll index, transpiration, CO 2 internal concentration, stomatal conductance, net photosynthesis, B content, grain yield and economic analysis. The relative chlorophyll index (RCI) of plants showed no significant effects at both 28 and 46 days after emergence (DAE). The extraction order of boron was boric acid > borax > FTE BR12 > Borogran. The application of boron did not affect the physiological quality (stomatal conductance, transpiration and internal concentration of CO 2 ). However, the net photosynthetic rate was lower when boric acid was applied in relation to other sources. The maximum production (4,446 kg ha -1 ) was obtained using 1.35 kg ha -1 of B with the use of boric acid. However, according to an evaluation of economic viability, it is observed that there are economic differences among sources of boron and evaluated doses. The application of 4 kg ha -1 of borax provides the highest economic return.

RESUMOO objetivo deste estudo foi obter indicadores econômicos da produção de alface crespa (Lactuca sativa) em cultivo sucessivo a plantas de cobertura, em sistema de plantio direto. O delineamento experimental foi em blocos casualizados, sendo seis tratamentos com plantas de cobertura: crotalária (Crotalaria juncea), feijão de guandu (Cajanus cajan), feijão de porco (Canavalia ensiformis), milheto (Pennisetum glaucum) e sorgo (Sorghum bicolor), além de um tratamento controle, com uso de vegetação espontânea, com quatro repetições. Foi avaliada a produtividade e estimados os indicadores econômicos para uma área de produção de 1000 m 2 . Observou-se que o cultivo de alface em sucessão ao sorgo forrageiro e manutenção da palhada sobre o solo propiciou aumento da produtividade e dos ganhos monetários. O lucro operacional obtido com a produção de 3,05 toneladas de alface cultivado em canteiro contendo palhada de sorgo foi de R$ 3.754,35. Este valor superou em R$ 608,06, R$ 1.269,60, R$ 4.052,28 e R$ 3.361,44 os valores obtidos com o cultivo em pré-safra de milheto, feijão de porco, feijão guandu e crotalária, respectivamente, além do tratamento controle, em R$ 2.426,80. Desta forma, recomenda-se a utilização do sorgo forrageiro como cultura antecessora a produção de alface crespa em sistema de plantio direto.Palavras-chave: custos de produção; hortaliças; indicadores econômicos; Lactuca sativa Economic analysis of the production of crisp lettuce in successive cultivation of cover crops under no-till system ABSTRACT The objective of this study was to obtain economic indicators of the production of crisp lettuce (Lactuca sativa) in successive cultivation to cover plants under no-tillage system. The experiment was carried out in a randomized block design, with six treatments: Crotalaria (Crotalaria juncea), guandu (Cajanus cajan), jack bean (Canavalia ensiformis), millet (Pennisetum glaucum) and sorghum (Sorghum bicolor), in addition to a control treatment, with the use of spontaneous vegetation, with four replications. The productivity was evaluated and economic indicators were estimated for a production area of 1000 m 2 . It was observed that the cultivation of lettuce in succession to forage sorghum and maintenance of the straw on the soil provided an increase in productivity and monetary gains. The operational profit obtained with the production of 3.05 tons of lettuce cultivated in beds containing sorghum straw was R$ 3,754.35. This value exceeded R$ 608,06, R$ 1,269.60, R$ 4,052.28 and R$ 3,361.44 the values obtained with the pre-harvest millet, jack bean, guandu and crotalaria, respectively and R$ 2.426,80 the control treatment. Thus, the use of forage sorghum as a predecessor crop is recommended to produce crisp lettuce under no-tillage system.