For many types of crops, hybrid strains have been developed that have been found in test plantings to produce significantly higher yields than were produced by traditional nonhybrid strains of those crops planted alongside them
However, in many parts of the world where farmers have abandoned traditional nonhybrid strains in favor of the hybrid strains, crop yields have not increased
The hybrid strains were tested under significantly better farming conditions than are found in most areas where farmers grow those strains.