Clint Shock and Peter Sexton
Western Region Project W-128: Microirrigation: Management Practices to Sustain Water Quality and Agricultural Productivity, Maui, HI, September 20-22, 2000
Malheur Experiment Station, OSU, 595 Onion Ave., Ontario,
OR 97914 Telephone (541) 889-2174 Email Clinton.Shock@oregonstate.edu
Central Oregon Agricultural Research Center, OSU, 850 Dogwood Lane, Madras, OR 97741 Telephone (541) 475-7107
Drip irrigation systems are being intensively tested on alfalfa for seed, potatoes, onions for bulbs, onions for seed, poplar trees, yew shrubs, and carrot seed. Observations are also being made on drip system serving mint, sugar beets, and wheat fields. Treatments are being evaluated based on crop yield, crop quality, and water use efficiency.
1. Irrigation criteria for alfalfa seed.An alfalfa seed field was established in 2000 that will be irrigated uniformly with SDI until bud formation, then at 4 different levels of crop evapotranspiration (Etc ) demand (20, 40, 60, and 80%) with 5 replicates of each treatment in 0.2 acre plots. Each treatment will be irrigated twice a week to replace the fraction of evapotranspiration used in the last 3 to 4 days. It is anticipated that optimal seed production will occur with considerable water stress. Soil water will be measured in the alfalfa seed field with capacitance probes.
2. Tape configuration in alfalfa seed: Tape placement and alfalfa plant spacing for the alfalfa seed above is as follows: the alfalfa is 30 inches between rows and there is 5 feet between the tapes. Tape buried 12 inches deep between every other row of alfalfa will be compared with tape buried as deep as mechanically possible; 15-18 inches deep between every other row of alfalfa.
3. Irrigation criteria for potato. Potatoes were grown with successively drier irrigation criteria ( -15, -30, -45, and -60 kPa) with five replicates of each treatment. A single drip tape served two rows of potatoes to reduce tape cost, enhancing economic feasibility. Soil water was monitored automatically every hour using granular matrix sensors. Plots were irrigated automatically as often as every 6 hours, as required.
4. Tape placement for potatoes: The potato rows were spaced 3 feet apart. The treatments resulted in tapes 3 or 6 feet apart, respectively.
1. Buried 3-4 inches below the soil surface over every potato seed piece row.
2. Buried 3-4 inches deep between two rows of potatoes in a single raised bed.
5. Leaching avoided: Three vertical grids of soil moisture sensors were used in the soil perpendicular to the potato crop rows and drip tapes to evaluate vertical and horizontal soil water movement. (The soil in all the other trials were measured for soil water potential or soil water content.)
6. Reduced N applications: Onions were grown using 0, 50, 100, 150, 200, 250, and 300 lb N/acre with an irrigation criterion of -20 kPa. The N was split into small increments during the season. Both the current N recommendations and commercial applications are in the range of 300 to 350 lb N/acre. The resulting onion bulb yield and grade will be evaluated after conventional storage. The economic value of the crop will be estimated as well as the most environmentally sound and economically advantageous N rates.
7. Soil moisture monitoring in growers' drip-irrigated onion fields. Soil water potential was monitored using GMS every 8 hours in three cooperating growers' fields.
8. Demonstration of the continuous use of tape. Tape was buried 6-8 inches deep on a cooperating farm in 2000 (Ontario Farms, Ontario in cooperation with David Blaylock) where a sequence of crops is being planted to establish the variability of long term use of tape in the same field without removal. Onions, wheat, and sugar beets are being grown in rotation in successive years on 3 acre plots. Mint is being grown on an additional 3 acres with long term SDI. These plots have been monitored for water application and soil moisture in 2000. Water flow measuring and soil moisture monitoring equipment were installed this spring.
9. Hybrid poplar water use and irrigation systems.Five irrigation treatments are being evaluated to increase irrigation efficiency: three irrigation rates using mini-sprinklers and two alternative drip irrigation systems. Water application, soil water potential, applied water, and tree growth are being measured in all four replicates of the trial.
10. Carrot seed. Carrot grown for seed is a very important high-value crop in central Oregon. Disease tolerances are low in the crop, particularly Alternaria radicina and A. dauci. Employing a subsurface drip system to deliver irrigation water may decrease potential for disease infection and spread within the carrot canopy and may provide long term benefits of decreasing water and fertilizer use. Towards this end, a preliminary trial is being conducted to observe carrot yield and disease incidence with five different irrigation thresholds (-15, -30, -60, -90, and -120 kPa soil water potential). The first season of this trial is almost completed.
11. Onion seed. Onion grown for seed is a very risky, but potentially very profitable, crop. The fungus Botrytis allii may blight seed stalks, umbels, and florets in onion and has been known to cause complete stand loss. As with carrots, SDI may provide benefits in decreasing disease spread and so decrease some of the risk associated with this crop. A preliminary trial using SDI in seed onion is being conducted to look at the effect of tape placement (0, 5, 10, and 20 cm depths) on disease incidence and yield.
12. Water stress on yew. Hicksii yews are being grown experimentally under variable water stress using SDI to optimize taxol production. The effect of water stress on other chemical components in the yew leaves is currently being examined.
References
Journal articles:
Shock, C.C., J.K. Ishida, E.P. Eldredge, and M. Seddigh. 2000. Yield of yellow onion cultivars in eastern Oregon and southwestern Idaho. HortTechnology. 10:613-620.
Shock, C. C., E. B. G. Feibert, and L. D. Saunders. 2000. Irrigation criteria for drip-irrigated onions. HortScience. 35:63-66.
Hoffman, A.M., C.C. Shock, and E.B.G. Feibert. 1999. Taxane and ABA production in yew under different soil water regimes. HortScience. 34:882-885.
Other selected articles:
Shock, C. C., E. B. G. Feibert, and L. D. Saunders. 2000. Nitrogen fertilization and plant population for subsurface drip-irrigated onions. Oregon State University Agricultural Experiment Station, Special Report 1015. pp. 45-51.
Shock, C. C., E. B. G. Feibert, and L. D. Saunders. 2000. Irrigation management for hybrid poplar production, 1997-1999. Oregon State University Agricultural Experiment Station, Special Report 1015. pp. 80-93.