This study aimed to characterize the harvest phenological stages of soybean cultivars intended for silage. Cultivars were evaluated for dry weight of the composite sample, branches, leaves and pods; wet mass of branches, leaves, pods and ground natural matter. This experiment was a 3 x 2 factorial randomized block design, with four replications each, where the first factor corresponds to the harvest stage: R4, R5 and R6; and the second factor refers to two soybean maturity groups (8.0 and 8.1). A significant interaction was detected only for ground natural matter. Higher values of most traits evaluated were observed for the R6 harvest phenological stage. The cultivar with maturity group 8.0 showed higher values for ground natural matter.

No abstract

A época de semeadura e o cultivar adaptada a cada região são fatores importantes para se obter a máxima produtividade de soja. Conhecer quais caracteres influenciam, de forma direta ou indireta, para a obtenção da maior produtividade, torna-se viável e por isso objetivou-se avaliar o efeito da época de semeadura em três cultivares com grupos de maturação (Semiprecoce, Médio e Semiprecoce, respectivamente) e de soja na região de Francisco Santos - PI. O experimento foi conduzido na fazenda Joaquim Isac na cidade de Francisco Santos Piauí, localização geográfica 6º 59 34 S 41º 8 16 W; 270 m de altitude. O delineamento experimental foi instalado em blocos casualizados com quatro repetições em esquema fatorial 4x3, totalizando 12 tratamentos. O primeiro fator constituiu de quatro épocas de semeadura: 30/12/2015, 06, 13, e 20 /01/2016. O segundo por três cultivares com grupos de maturação 8,2, 8,6 e 8,3. Observou-se efeito significativo da interação (CxE) para a maioria dos caracteres, exceto para a variável peso de mil grãos. Os elementos climáticos nas quatro épocas de semeadura na safra 2015/16 afetaram diretamente o desenvolvimento e produtividade da soja, sendo a segunda época a mais adequada; o cultivar 2 apresentou-se melhor que as demais e os caracteres número de grãos por planta e massa seca de caule produziram causa e efeito na produtividade de grãos em soja podendo ser recomendado na seleção direta com a produtividade.

This study aimed to evaluate the growth and development of watermelon plants under different plant spacings in the Semi-arid region of Brazil. A randomized block experimental design was used with four treatments and eight replications. Data were submitted to analysis of variance and the Tukey test. The treatments were composed by the following spacings: T1: 3.0 x 0.8 m; T2: 3.0 x 0.6 m; T3: 2.0 x 0.8 m and T4: 2.0 x 0.6 m (spacings between rows and between plants, respectively). The plant length, number of leaves, stem diameter, leaf area, number of flowers, number of fruits per plant, average fruit weight, total fruit production, number of commercial fruits, average weight of commercial fruits, total weight of commercial fruits and percentage of commercial fruits were evaluated in this study. There was a significant difference in the growth traits: stem diameter and leaf area at 30 days after sowing (DAS), and plant length, stem diameter and number of leaves at 60 DAS, with no significant statistical difference in the remaining days and nor for the number of flowers. The watermelon plants showed adequate vegetative and productive development at the 2.0 x 0.8 m plant spacing in the edaphoclimatic conditions of the semi-arid region under study. This spacing is well suited to small producers in the semi-arid region, which are dependent on agriculture with small areas and can obtain good productivity with no need to use larger areas due to spacing

Soybean has economically stood out worldwide. In MATOPIBA region of Brazil (Maranhão, Tocantins, Paiuí e Bahia) it is the most economically important crop with participation in the country’s GDP growth. Due to this great growth economic and the incentive to the production of this oilseed, this study aimed to understand the behavior and physiological quality of soybean genotypes and to determine the productive potential of soybean seeds of different cultivars in the Cerrado of the State of Piauí. To this end, an experiment was carried out at Celeiro Farm, located in Serra do Quilombo, municipality of Monte Alegre do Piauí. Sowing followed the usual standards and was carried out on January 10, 2016. The experiment was set up in a randomized complete block design with four replicates. The treatments consisted of five cultivars of INTACTA RR2 PRO soybean, with different maturity groups: C1: MG 8.6, C2: MG 8.3, C3: MG 8.6.1, C4: MG 7.9 and C5: MG 8.5. The analyzed variables were: plant height, number of nodes, internode length, pod length, number of grains per pod, number of grains per plant, one thousand seed weight, productivity, first germination count, germination, seedling length, germination speed index and seedling dry mass. The results indicated that the best cultivars were: C5:TMG 2185 IPRO for plant height, internode length and pod length, and C4: BÔNUS IPRO for number of grains per pod, number of grains per plant, one thousand seed weight, and productivity. Considering the first count, germination, and germination speed index, the best cultivar was C5.

The world economic importance of soybean (Glycine max (L).) crop is consolidated, and tests to verify the best sowing season for yield gain of cultivars are demanded. The aim of this study is to analyze the effect of sowing season on soybean cultivars of different maturity groups, since the determination of the optimum time for planting soybeans and the cultivar most suited to the region under study can increase yield components and consequently productivity. The experiment was conducted in Currais, State of Piauí, Brazil, and involved evaluation of 12 treatments resulting from the interaction between: 1) sowing seasons: 11/22/2014; 11/29/2014; 12/6/2014; 12/13/2014; 12/20/2014 and 12/27/2014 and 2) two cultivars of maturity groups 8.2 and 8.6. The experiment was a randomized complete block design with four replications, in subdivided plots, and the nested effect in the plot was sowing dates. Data were analyzed using ANOVA and Tukey's test (p  0.05). Interaction was significant for number of pods, pod length, dry mass of stem, dry mass of pods and number of grains per plant, but not for productivity and one thousand seed mass. In the agricultural year 2015/2016, the climatic factors worked directly on the components of soybean production, and it is possible to adopt any period of November and December for its planting.

The use of machines in the rural sector increases crop productivity in the field, making it essential to use these technologies for a successful rural enterprise in the market. In this way, this study aimed to analyze the current situation of agricultural mechanization in farms of small producers. The study was conducted in State of Piauí, in Brazil with 30 farmers in the region. This was a quantitative and qualitative research, developed as a questionnaire applied by direct interview. Data were analyzed and represented in graphs using SigmaPlot ® 12.0. It was concluded that the use of agricultural machinery for cultivation by small producers in the region studied is almost non-existent due to low purchasing power and also because they are small areas. Thus, the own family comprises most of the hand labor, working with crops in the field primarily by hand, leaving only more difficult services to be performed, such as disking, land clearing and threshing for agricultural machinery.

The objective of this study was to find the best potassium dose to increase soybean yield, taking into account the economic viability of the crop in the studied region. Sixteen treatments of the interaction between potassium doses (0, 50, 100 and 150 kg ha-1) and application times (sowing, vegetative stage (V3), vegetative stage V3 + reproductive stage (R1) and reproductive stage). The experiment was set up in a randomized complete block design with four replications. Plant growth and production characteristics were analyzed and a preliminary analysis of variance was applied to check the significance of the interactions for each characteristic by Tukey’s test (α = 0.05). Subsequently, the regression analysis was performed using SAS software (2013). The economic analysis was made using the Monte Carlo methodology (Lima, 2008), and processed with the software @Risk 7 (PALISADE, 2016). Potassium fertilization was positive with increase in yield, but there was no direct relation with the application period. The 109 KCl ha-1 dose provided greater economic viability in soybean cultivation.