Abstract
Knowledge about soil water availability for future planning is the basis for carrying out its rational use. This work aimed to study the spatiality of water precipitation, crop evapotranspiration, and the need for water supplementation in soybean cultivation in the microregions of Jales-SP and Andradina-SP for the summer harvest. The water balance was determined by the Thorthwaite and Mather (1955) method, with data made available by the Agrometeorological Stations Network operated by the Hydraulics and Irrigation area of UNESP Ilha Solteira. We considered an available water capacity (AWC) of 40 mm. The study took place from the simulation of the water condition of a soybean crop sown on November 4, 2020. In the water deficit condition, the actual evapotranspiration (ETa) was considered null at a 20 % deficit, and the other values followed the same mathematical proportion. The mean rainfall of the period, crop evapotranspiration, and water deficit of each weather station were interpolated through ordinary circular kriging in ArcGIS 10.7 software. The water deficit in the soybean crop in the northwest region of São Paulo is related to the poor distribution of precipitation during the cycle and the significant recurrence of Indian summers all through the area. For the producers’ safety, investment in irrigation systems anticipating this poor distribution is justified. The water deficit in the region is variable. In years with good rainfall distribution, it can reach zero values, and in years with poor distribution, it can reach values greater than 180 mm.
Highlights
Soybean (Glycine max L.) is the main crop of Brazilian agribusiness, with a cultivated area of approximately 35.8 million hectares producing 115 million tons per harvest
Due to the expansion of the Brazilian agricultural frontier in recent years, oilseeds are already being cultivated in regions with rainfall limitations through water supplementation carried out via irrigation system (MONTOYA; PINTOS; OTERO, 2017)
To obtain information about precipitation, water demand, and need for supplementary irrigation for the crops, we used data from eight climatological stations belonging to the Agrometeorological Network of Northwest São Paulo monitored by the Hydraulics and Irrigation area of the São Paulo State University “Júlio de Mesquita Filho” (UNESP) Ilha Solteira Campus
Summary
Soybean (Glycine max L.) is the main crop of Brazilian agribusiness, with a cultivated area of approximately 35.8 million hectares producing 115 million tons per harvest. Water availability is the main challenging factor for soybean yield. Most soybean crops in the world are carried out under the rainfed system. Due to the expansion of the Brazilian agricultural frontier in recent years, oilseeds are already being cultivated in regions with rainfall limitations through water supplementation carried out via irrigation system (MONTOYA; PINTOS; OTERO, 2017). Water loss to the atmosphere by transpiration seems to be an inevitable consequence of photosynthesis in the terrestrial environment. Carbon gas (CO2) absorption is coupled to water loss via a common diffusion route: as CO2 diffuses into the leaves, water vapor diffuses outward (TAIZ et al, 2017)
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