Table 1 shows the general growth and daily water use relationship for soybeans. Most growers realize the need to irrigate when the crop is blooming and setting pods. Experience indicates, however, that many growers tend to be late with the first irrigation and then quit before the crop can reach its full potential. The lack of early and late season irrigation is often responsible for a soybean crop not reaching its irrigated yield potential. The timing of irrigation is commonly referred to as irrigation scheduling.
Correct timing is critical to maximizing yield.
Having the ability to irrigate is important, but it is also essential that a grower have a commitment to apply irrigation in a timely manner. Too often growers irrigate by the appearance of the crop. Visual stress, especially during bloom and pod set, results in yield loss. Also, once irrigation is started, the time required to finish a field will result in part of the crop suffering even greater stress. If the soil moisture can be determined, then irrigation timing decisions can be improved.