Nutrient Management Research Database
General Information
Research Title
Research Specifications
Authors
Summary/Abstract from Original Source
Precision management of irrigation and fertigation in orchards is compromised by the physical constraints of traditional sprinkler and drip systems, which are designed for uniform nutrient delivery and ignore the reality that demand varies across fields and between individual trees. Trees that die from flooding or other damage are replanted and do not have the same water and fertilizer requirements as older trees. When applied uniformly, water and fertilizer may leach in light textured soils and pool in heavy soils. Emitter clogging and irrigation line damage further compound the problem of delivering water and fertilizer based on demand. Controlled application of water and dissolved fertilizer through a network of intelligent microsprinklers could lessen these problems. A microsprinkler system was developed to provide spatially variable delivery of water and fertilizer, and a prototype was installed in a nectarine orchard at the University of California in Davis. Fifty individually addressable microsprinkler nodes, one located at every tree, each contained control circuitry and a valve. Low-cost microcontrollers were programmed to communicate on a wired network laid along each row of the orchard. Latching valves provided a low-energy means of controlling flow to each microsprinkler. Pressure sensors connected to some of the nodes provided lateral line pressure feedback. A small computer board in the field (i.e., drip line controller) stored schedules and issued commands to each node. The nodes and drip line controller were operated on a single battery with solar-powered recharger. The system was programmed to irrigate individual trees for specific durations, to apply a specific volume at each tree, or to irrigate in response to soil water demand. Time-based schedules demonstrated the ability to provide microsprinkler control at individual trees, but exhibited discharge variation due to pressure differences between laterals. Volume-based schedules used pressure sensor feedback to more accurately control the volume applied by individual microsprinklers, and the average error in application volume was less than 4%. The 2 coefficient of variation for application volume improved from 4.1% for time scheduled control to an average of 2.5% for volume scheduled control. Soil-moisture-based schedules showed how an individual or a group of microsprinkler nodes could be triggered using a soil moisture sensor to irrigate at specific thresholds. Fault detection was used to check for damaged drip lines and clogged or damaged emitters. A pressure monitoring routine automatically logged errors and turned off the microsprinklers when drip line breaks and perforations caused pressure loss. Emitter diagnosis routines correctly identified clogged and damaged microsprinkler emitters in 359 of 366 observations. The system was effective for spatially variable control but suffered from trouble with wiring connectors, difficulty of installation, and the potential for problems associated with long-range wired communication and damage from animals and machinery. To alleviate these problems we explored the possibility of wireless communication between nodes. A prototype node was developed and results indicate that wireless control could be a feasible alternative to a wired system.
Research Highlights
Design and Methods
Results
- A prototype computerized microsprinkler systems designed to apply tree specific rates of water and fertilizer was installed in a nectarine orchard.
- The computer system allowed for the development of time-based schedules of water and fertilization applications.
- While the wired system suffered from connector issues, another wireless system was explored as an alternative.
- The costs of the system developed were prohibitive, and would not be economically feasible unless outweighed by savings in water and fertilizer expenditures.
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