WSP10689 - Laserfiche WebLink

Home Browse Search

~ f-,o .~ .~ -, since then, data collection, processing and evaluations have \;2 improved tremendously, providing us with more accurate data. In 1988 and 1989, one-third of the sites monitored had sprinkler systems.. This could have affected the average (includes surface + sprinklers) deep percolation. and irrigation efficiency for those two years. Data from 1990 through 1993 shows increasing irrigation efficiency and decreasing deep percolation and water application trend. Of the 16 original sites started in 1985, only three were monitored . through 1993: sites 39,16 and 21. Of the three sites, only one site, 39 still has the same crop as 1985. In the Grand Valley, fields that are in annual crops or alfalfa go through a crop rotation. This makes it impossible to compare individual monitored '~ites for different years. comparison of nine years of irrigation monitoring data by crops (Table 6) show no significant trend toward decrease in water use or deep percolation for row crops (annual). Perennial crops like alfalfa and orchards are showing increasing efficiency and decreasing deep percolation in the last few years. Alfalfa water application has been decreasingE;ince' 1990. .; Until. good irrigation water management is applied in the field.to significantly reduce the amount of water use and deep per~rylation, a change will not be seen. Salinity Trends: During the fall, for' the past nine years (1984- 1993), quantitative' salt determinations have been made at depths of 6, 18, and 30 inches for each monitoring site. Soil samples were {~ collected each year from approximately the same area within the monitored field. Each monitoring site was sampled in two locations, the top and the bottom of the monitoring fields. At most sites, soil salinity levels are relatively low (refer to Appendix F for salinity data). Fifty to seventy years of irrigating these soils have reduced salinity levels to very low ~~lties~ . . i During this ten year period, 41 different sites have been monitored for quantitative salt determination. Of these 41 sites, 13 sites have been monitored for a period of seven years or more. These sites have shown no trend of increased salinity level..; Salinity levels would not be expected to rise on these deep, well drained soils, since net seasonal .irrigation application is greater than the crop needs. Water'applied in excess of the crop needs---" keeps the salts leached out of the root zone; , . changes in salinity from year to year on the monitoring.sites is probably a result of management practices rather than irrigation practices. There does not appear to be any trend for increase or decrease in soil salinity for the 13 sites which have been monitored for a period 'of seven years or more. ! .:....;... 24