ABSTRACT The sizing of mechanized agricultural systems depends on the soil and climatic conditions, the crop and the work regime. The aim of this study was to determine the probabilities of time available during an agricultural year for mechanized spraying and sowing in the northeast region of the State of Mato Grosso do Sul and south of Goiás. The meteorological restrictions imposed as unfavorable hours were: ambient temperature above 32°C, relative air humidity below 50%, wind velocity above 15 km h-1 and soil volumetric moisture above 39% (humidity equivalent to 90% of the available water capacity for the studied soil). The mathematical models were elaborated for eight years, based on the historical data of the automatic station of the National Institute of Meteorology installed in the region. It was possible to determine the time available for mechanized sowing and agricultural spraying operations. The available times for every ten days of the agricultural year for mechanized spraying and sowing in the study region were determined. The hourly water balance is used for the restrictive study of soil moisture in determining the time available for mechanized operations. A single self-propelled sprayer (30 m bar) and a single seed drill (48 rows) are not sufficient to meet the operational rate in an area of 3,000 ha in the northeast of the state of Mato Grosso do Sul and south of Goiás.

RESUMO A qualidade física do solo é um dos fatores mais determinantes no desenvolvimento de qualquer cultura. Este trabalho teve, como objetivo, avaliar a representatividade amostral nos mapeamentos da resistência mecânica do solo à penetração nas linhas e entrelinhas no cultivo do algodoeiro, sob duas condições de umidade. Foram amostrados 30 pontos de controle em um talhão de 91 ha cultivado com algodoeiro. Foram realizadas leituras da resistência mecânica do solo à penetração (RP) e de umidade nesses pontos georreferenciados. Independentemente da umidade do solo é indiferente o posicionamento amostral da resistência mecânica do solo à penetração (linha, entrelinha ou em ambas as posições) quando a camada analisada é maior que 0,20 m no cultivo do algodoeiro. A diminuição da umidade do solo ocasiona o aumento dos valores da resistência mecânica do solo à penetração, independentemente do posicionamento amostral.

ABSTRACT The soil physical quality is one of the most determinant factors for the development of any crop. This study aimed to assess the sample representativeness in soil resistance to penetration mappings taken in rows and interrows of the cotton crop, under two soil moisture conditions. Thirty control points were sampled in a cotton field of 91 ha. Soil resistance to penetration and soil moisture were measured at these georeferenced points. Regardless of soil moisture, the sampling position of soil resistance to penetration is indifferent (row, interrow, or in both positions) when the analysed depth is greater than 0.20 m in the cotton crop. The decrease of soil moisture causes the increment of soil resistance to penetration, regardless of the sampling position.