Agriculture irrigation accounts for approximately 80 percent of the consumptive ground and surface water use in the United States (Schaible and Aillery, 2012). Recently, acreage of irrigated land for row crop production has increased in humid regions (Figure 1), leading to the need for optimizing water use in these systems to conserve water resources and bring economic beneft to producers. Soybean water use varies with growth stage (Figure 2). Soil water sensors are one tool that can be utilized to better assess soil water availability in the soil profle and schedule irrigation appropriately during soybean growth stages.

To determine the latest efective soybean growth stage to initiate irrigation and maximize yield for soybean plants.

Irrigation decisions are based on the needs of the crop and may vary from one year to the next. Furthermore, environmental factors such as diverse rainfall patterns, soil type, soil water availability, heat waves and high evaporative demand need to be considered. For example, in sandy soils, soybeans are more likely to require irrigation in the late vegetative and early reproductive stages (V4 to R3), and providing adequate soil water in the later reproductive stages (R4 to R6) is even more critical.