Irkutsk region is rich in land that is suitable for agricultural activities. The total sown area of agricultural crops in the Irkutsk region is 759 thousand hectares (2019). The main place is occupied by grain and leguminous crops, the total area of which is 540 thousand hectares (71.1%). In their structure, the first place belongs to spring wheat, the second place is taken by spring barley, the third-by oats. Due to the need to strengthen the feed base, forage crops play an increasing role. Yield depends on many factors, primarily weather conditions. For photosynthesis, plant crops need sunlight. By the number of Sunny days, the Irkutsk region is not inferior to the Crimea. There are 221 Sunny days per year. If weather conditions are correctly predicted, a high yield can be achieved. To assess the absorption of solar energy by grain crops, the radiation balance was considered in this article. Photosynthetic plant pigments absorb light and convert it from solar energy to chemical energy, which results in active plant growth. To forecast the future harvest, it is necessary to calculate the intensity and duration of solar radiation, which is the most important condition for further production of agricultural products. A study was conducted on the effectiveness of using insolation in the Irkutsk region for sowing wheat. The radiation balance was compiled, which allowed us to identify the maximum solar radiation favorable for wheat growth. To determine the amount of effective radiation, measurements were made of soil temperature, air humidity, and meteorological conditions in the Irkutsk region.