Fertigation techniques for use with multiple hydrozones in simultaneous operation
Site-specific delivery of fertilizer is a useful tool to address differences in crop need. Modern systems with wirelessly networked sensors and valves allow multiple hydrozones to be created more easily than traditional wired systems. This allows irrigation and fertigation rates to be varied across small portions of a field. However, fertigation to multiple hydrozones with different fertilizer requirements may be complex if each zone cannot be fertigated in an independent set. Instead, it might be necessary to operate several fertigation zones simultaneously. This raises a concern over the ability to deliver fertilizer uniformly within each zone. Four fertigation strategies were tested. The conventional method was to fertigate multiple hydrozones at different times. Three site-specific strategies were considered, involving overlapping fertigation phases in multiple hydrozones. Fertilizer distribution uniformity tests were conducted with a 64-emitter drip line to determine which strategy gave the most uniform distribution of fertilizer within a hydrozone. All fertigation techniques performed well, with fertilizer distribution uniformities between 0.88 and 0.96. Selection of the optimum site-specific fertigation strategy will depend on crop needs, scheduling limitations, and system design parameters such as emitter type, fluid travel time, and slope. Similar to conventional fertigation, the main factor in fertilizer distribution uniformity for this study was drip emitter variability. In the presence of sloped terrain, the site-specific control strategy that involved a delay between fertilizer injection and flushing had the least uniform fertilizer application.