Center pivot irrigation

The low levels of rainfall in south-central Washington make irrigation a necessity. Rill, solid-set overhead sprinkler, drip, and center-pivot irrigation systems are all being used to some extent in the vineyards of the Northwest. 

In hot weather, evaporation pans lose up to one-half inch of water per day. Vineyards with cover crops lose up to 75 percent of evaporation pan losses. Up to 25 percent of the irrigation water can be lost through wind drift and evaporation. This results in a situation that is within 4 percent of a theoretical break-even input and output. To accomplish this break-even situation requires constant, twenty-four hour a day irrigation. While this concern is yet to be tested, past history with other crops has proved eminently successful. In 1978, 500 acres of V. vinifera grapes were planted under center-pivot irrigation. Since that time, an additional 1500 acres have been planted under center-pivot systems, so that today 2000 of the state s estimated 4500 acres of V. vinifera are utilizing center-pivot irrigation. 

A major advantage of this method of irrigation is cost. Solid-set sprinkler irrigation is estimated to cost in excess of 1100 per acre, or 151,800 for 138 acres. A center-pivot irrigation system is estimated at less than 60,000 for the same 138 acres. In both instances, an adequate water source at the site is presumed. 

With center pivot irrigation simulator equipment peanut and other vegetable oils were superior to paraffinic oils for applying A. cassiae spores at rates of 0.4-8 g spores/ha to sicklepod (Phatak, S. C., Univ. of Georgia, Tifton, GA, personal communication). Good infection occurred at rates of 0.8-1.6 L/ha of the oil/spore mixture even without dew. Sicklepod control was best when spores were applied in oil, compared with wettable powder or conidial suspension. 

Fig. 117.6 Center Pivot irrigation and the RPLSS in Kansas. (Photograph by Jonathan Leib)...

Splinter, W. (1976). Center-Pivot irrigation. Scientific American, 234(6/June), 90-99. 

Irrigation Irrigation water applied at 2-week intervals by an automatic, movable, center-pivot, overhead, sprinkling system capable of watering two 65-ha plots/day. About 3 h are needed to move the irrigation system. 

These data give some idea of the erratic areal distribution of aldicarb residue contamination even within a single field. For example, on Field 5, treated in its entirety in 1979 and in the eastern half in 1980, significant concentrations of residues were initially encountered only at two spots—at and directly north of the center pivot (sites 7 and 2, Fig. 1). Surprisingly, no residues were initially encountered in water from wells at positions 3, 4 or 5, or at any time in samples from the neighboring Field 4, all directly downgradient in the aquifer from the treated area. Residues (12 ppb) were found in June 1981 in water from the irrigation well which was cased to a depth of 36 feet (11 m), or 28 feet... 

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