A Revista Ciência Agronômica é voltada para estudos relacionados com as Ciências Rurais e Recursos Naturais

This study aimed to assess the efficiency of soybean seed distribution in the soil, which directly influences crop yield, using graphite as a solid lubricant, a common practice to improve seed dosing fluidity. The effect of sowing speed and seed chemical treatment on distribution in the furrow, final plant population, and yield was investigated. The experiment used Federer´s augmented block design with 10 treatments, five sowing speeds (4, 6, 8, 10, and 12 km h^-1) and two seed treatments (with and without 4 g of graphite lubricant per kilogram of seeds). High sowing speeds increased uneven seed distribution, while graphite lubricant significantly improved plant spacing and crop yield. This study reinforces the importance of precise sowing speed adjustment and proper seed treatment to optimize soybean plant distribution in the field. Graphite lubricant proved to be effective at reducing spacing failures and increasing crop yield. These findings underscore the relevance of precision agriculture and the use of technology to ensure efficient and sustainable sowing operations.

Techniques to monitor vegetation cover have been used to track the biomass and yield of agricultural crops. Quantifying the leaf area index (LAI) and its variation throughout the production cycle of soybean is important because this data can be used as an input variable in growth and productivity models. Field experiments were carried out during the 2017/2018 and 2018/2019 growing season in soybean crops at the Faculdade Marechal Rondon (FARON) in Vilhena, RO, Brazil, to measure the LAI of cultivar 75I77 RSF IPRO from the estimated extinction coefficient of photosynthetically active radiation (PAR). LAI measurements were performed weekly in the 2018/2019 crop season. The PAR data were collected using the PAR Apogee® SQ-316-S linear sensor. The light extinction coefficient (Kc) was calculated using LAI and solar radiation interception data. A Kc value of 0.687 was found for this crop, indicating that more than 68% of the light was intercepted by the plant structure. In addition, the LAI data estimated via Kc were compared with LAI values estimated with the CROPGRO-Soybean model. The first method estimated the LAI values better than the second, as the r² increased from 0.738 to 0.882, the difference was reduced from 19.9 to 13.3%, and the d-value changed from 0.815 to 0.952. Thus, the extinction coefficient method of PAR can efficiently estimate the LAI parameter in soybean.

Agrometeorological modeling is crucial to predict the impact of climatic conditions on agricultural production. However, its application in large regions faces challenges due to the lack of weather stations and limited access to real-time data. In this study, the multiplicative agrometeorological model was used to estimate soybean productivity in the seven municipalities of the Southern Cone of Rondônia in the 2020/21 to 2022/23 harvests. This model considers the relationships between actual and potential evapotranspirations and water conditions during different phenological stages. Ten-year water balances were developed for each municipality, using air temperature data from ERA5-Land from the ECMWF and precipitation data estimated by NASA’s GPM_v06 satellite. The results showed satisfactory performance of the model, with coefficients of determination ranging from 0.48 to 0.88 and agreement indices from 0.41 to 0.90 compared to the data observed by IBGE.

The response of second crop corn to nitrogen application was evaluated at different stages of development. The experiment was conducted on the São Carlos farm in Vilhena – Rondônia/Brazil. The factors under study included the splitting of N associated with the application of coated urea with NBPT (45-00-00) in top dressing. The control group (witness) showed the highest productivity among all treatments, with 7962 kg ha-1, followed by V3+V7 (7895 kg ha-1) and V4+V8 (7821 kg ha-1). The lowest productivity was 6630 kg ha-1 in V5+V9, indicating that the later the urea application in defining the productive potential of the crop (V4), the lower the yields achieved.