Os sistemas de manejo do solo podem resultar em alterações físicas no solo como a formação de camadas compactadas. Um dos atributos físicos mais adotados como indicativo da compactação do solo têm sido a resistência mecânica do solo à penetração, por apresentar relações diretas com o crescimento das plantas e por ser mais eficiente na identificação de estados de compactação do solo. Nesse sentido, objetivou-se avaliar a resistência mecânica do solo à penetração em dois sistemas de manejo do solo, por meio de utilização da técnica de penetrometria. O experimento foi realizado em área da Universidade Federal Rural da Amazônia, Campus de Parauapebas. O delineamento experimental utilizado foi inteiramente casualizado com dois tipos de manejo: sistema de plantio direto (SPD) e sistema de plantio convencional (SPC), com 40 repetições para cada tratamento. A resistência do solo à penetração (RP) foi mensurada utilizando-se o Medidor Eletrônico de compactação do solo por pressão, modelo PenetroLOG – PLG 1020 da marca Falker, na profundidade de 0,00 a 0,40m a qual foi subdividida em oito camadas de 0,05 m para avaliação. A adoção dos sistemas de plantio direto e plantio convencional ocasionaram oscilação na resistência mecânica do solo à penetração ao longo das camadas do solo. No SPC foi observada menor RP quando comparado ao outro tratamento, na profundidade 0,00 - 0,10 m. Diferente disso, no SPD as subcamadas de 0,15 - 0,25 m apresentaram menores valores de RP e maior umidade do solo. A partir da profundidade de 0,20 m ambos os sistemas apresentaram indicativo de camadas compactadas do solo.

Leucaena leucocephala is an arboreal legume with many applications in agriculture (forage, wood production, charcoal, soil improvement, shading, windbreak, and hedge). Its seeds show dormancy, which is caused by physical blockade through resistant and impermeable integument. The aims of this study were to evaluate and determine efficient methods for overcoming dormancy in Leucaena leucocephala seeds. The experiment was carried out in Tangará da Serra city, Brazil, adopting a completely randomized design, with four replications. The treatments consisted of no scarification (T 0), scarification with sandpaper (T 1), immersion in concentrated H 2 SO 4 for 5 min (T 2), 10' (T 3), 15' (T 4), and 20' (T 5), and immersion in water at 80°C for 5' (T 6), 10' (T 7), 15' (T 8) and 20' (T 9). The seeds were placed in germination chamber at a temperature of 25ºC and photoperiod of 12 hours day/night over a period of 10 days, for all treatments, using 50 seeds per replicate. The experimental data were submitted to analysis of variance (type I error) by F test (p<0.05) with comparison of averages performed by Tukey test (p<0.05). The treatment that showed best efficiency in overcoming seed dormancy was immersion in concentrated H 2 SO 4 (density of 1.84 and purity of 95%) for 20 min, with 93.0% of viable seed germinated. Immersion of seeds in water at 80ºC for 20 min (0.0% seed germination) showed lowest efficiency in overcoming dormancy of Leucaena leucocephala seeds. It was concluded that treatment with immersion in concentrated H 2 SO 4 for 20 min is the most efficient in overcoming dormancy of Leucaena leucocephala seeds, showing higher values of first germination count, germination percentage, germination speed index and average time of germination.

The mapping of pastures can serve to increase productivity and reduce deforestation, especially in Amazon Biome regions. Therefore, in this study, we aimed to explore precision agriculture technologies for assessing the spatial variations of soil pH and biomass indicators (i.e., Dry Matter, DM; and Green Matter, GM). An experiment was conducted in an area cultivated with Panicum maximum (Jacq.) cv. Mombaça in a rotational grazing system for dairy buffaloes in the eastern Amazon. Biomass and soil samples were collected in a 10 m × 10 m grid, with a total of 196 georeferenced points. The data were analyzed by semivariogram and then mapped by Kriging interpolation. In addition, a variability analysis was performed, applying both the Normalized Difference Vegetation Index (NDVI) and Normalized Difference Water Index (NDWI) derived from satellite remote sensing data. The Kriging mapping between DM and pH at 0.30 m depth demonstrated the best correlation. The vegetative index mapping showed that the NDVI presented a better performance in pastures with DM production above 5.42 ton/ha−1. In contrast, DM and GM showed low correlations with the NDWI. The possibility of applying a variable rate within the paddocks was evidenced through geostatistical mapping of soil pH. With this study, we contribute to understanding the necessary premises for utilizing remote sensing data for pasture variable analysis.

The correct seeder-fertilizer adjustment is responsible for increasing the efficiency of corn cultivation's implementation process. This work aimed to evaluate transmission system regulation of seeder-fertilizer seed deposition unit in maize crop implantation in the Eastern Amazon. The experiment was carried out after the sowing process with a seeder-fertilizer for conventional planting with a mechanical seed distributor. The treatments resulted in five size combinations of driven gears (8, 10, 12, 15, 17) with the motor gear of size 7, which resulted in the respective corn sowing densities, 64.978, 62.311, 52.444, 44.977, 38.665 plants ha-1. Each treatment consisted of a 200 m seeding strip divided into 20 plots per strip (treatment). The agronomic variables analyzed were: average Number of Days to Emergence (NDE), longitudinal distribution of plants in the standard (N), Fault (F) and Double (D) fields, Initial Plant population (IP), Final Plant population (FP), Stem Diameter (SD), Plant Height (PH), Number of Leaves (NL), Number of Ears (NE), Mass of one hundred grains (MG), Number of Grains per row (GR), Number of Ear rows (ER), Ear Length (EL), Ear Diameter (ED) and Productivity (P). Data were submitted to statistical analysis, correlation test and decision tree analysis. The decision tree showed which initial population was more important to classify the most relevant agronomic variables in corn planting. The initial stand of 62.442 plants ha-1 was the most suitable for corn in the Amazon region. There is potential to reach corn productivity of 5.14 to 5.33 t ha-1 when combined with a drive gear 12 and driven gear 7 seeder-fertilizer machine transmission system

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The application of precision agriculture in cocoa and papaya cultivation in Brazil is still incipient. This study aimed to evaluate the spatial variability of the physical attributes of soil cultivated with a consortium of papaya and cocoa. The study was conducted in two sampling grids of 50 points, in two areas cultivated with papaya and cocoa with different planting times (three and eleven months). The soil attributes soil resistance to penetration (RP) and soil gravimetric moisture (UG) were determined at soil depths of 0–20, 20–40 and 40–60 cm. The data were submitted to an exploratory and descriptive analysis. Subsequently, a geostatistical analysis was performed to quantify spatial dependence and then interpolation of the data through kriging. The maps showed weak spatial variability for the UG and RP. In the two areas, it was observed that the depth of 0–20 cm had a lower RP (1.7 Mpa) and a higher UG (40 g g−1), and as the depth was higher, had a higher RP (4.4 Mpa) and a lower UG (38 g g−1). Area 1 presented higher RP values in depth, showing greater susceptibility to compaction. The area characterized by the consortium of papaya and cocoa presented more susceptible to compaction. The mechanical resistance of the soil to penetration was more critical in the 40–60 cm layer for the two consortia evaluated, evidencing areas with possible restriction to plant growth.

The reduction in the leaf area is one of the causes in the fall in soybean (Glycine max) productivity as it depends on the production of photoassimilates generated by the leaves, so any factor that interferes in its leaf area may affect the production. The attack of defoliating insects is among such factors. They cause a marked drop in grain yield due to its direct action, therefore, reducing the leaf area, consequently reducing the photosynthetic rate of the plant. The agronomic characteristics of the cultivars may interfere on the level of tolerance of the plant to this type of stress. The objective of this study was to evaluate the influence of defoliation levels on the vegetative and reproductive stages on the development and yield of grains in soybean cultivars. The experimental design was in randomized blocks, in a 2&times;11&times;2 factorial scheme, with four replicates. Factors consisted of defoliation stage (vegetative and reproductive), treatment levels (T1-control plant and ten treatments of artificial defoliation) and soybean cultivars (BRS 9090 RR and BRS 8890 RR). The following variables were evaluated: grain yield, dry mass of the pod, leaf dry mass, stem and root dry mass, plant height, stem diameter, number of leaves per plant, length and width of roots. It was observed that the defoliation had a negative effect on the productivity components of the cultivars, with the highest decrease in the reproductive stage, except for the treatment R5, 100% defoliation at the R5 stage, which was also reduced. In relation to the cultivars, the BRS 8890 RR was 27% better in grain yield in relation to BRS 9090 RR.

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