An exergy analysis of the bioconversion of radiation energy by plants during photosynthesis is substantiated for the first time. A computer system is developed for optimizing yield formation and determining the level of efficiency of agrotechnologies with consideration of the ecological conditions of agricultural lands. A method of combined exergy analysis of bioconversion of solar energy by plants and technogenic energy in agrotechnolgies is examined: from selection of plant species, varieties, and hybrids for correspondence to ecological conditions of the land to a quantitative estimation of the exergy content in the yield. It is shown that such analysis is the theoretical basis for predicting yield.