The inoculation of extensive crops with Azospirillum spp. has been extensively evaluated worldwide, with abundant information describing its role in enhancing early growth, nitrogen uptake, and final grain yield under diverse field conditions. This chapter presents the design and outcomes of inoculation with Azospirillum brasilense and Azospirillum argentinense field trials performed across different continents, under a wide range of environmental and agronomic management. The chapter covers inoculation studies performed on seeds, in-furrow during sowing, or as foliar on top of the crop canopies using diverse formulations. On average, the introduction of Azospirillum spp. to large-scale crops resulted in a 10% increase in grain yield over non-inoculated controls. The responses were variable, reflecting interactions among crop types, environmental conditions, and inoculationApplication strategies. In rainfed wheat (Triticum aestivum L.) trials conducted in semiarid regions, 60–200 observations per season were required to detect statistically significant yield effects depending on rainfall patterns, highlighting the importance of robust experimental designs. The analysis of response distributions offers a realistic approach to evaluate productivity under abiotic stress while enabling probabilistic assessments of inoculation outcomes. Studies on soybean (Glycine max L.) showed co-inoculation with Azospirillum and Bradyrhizobium spp. enhances nodulation and yield stability, particularly under stressed environments. The use of Azospirillum spp. inoculants is a complementary practice to enhance crop performance mostly under temperate and semi-arid cropping systems worldwide.