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<br />I~ <br />~q <br />n <br /><;-.' Add i t i ana II y, about 10% of 0 I d peach trees may have been tota II y <br />o.~',> damaged and part i a II y damaged trees may have lost about 10% of the i r <br />-'fruit bearing surface. According To Rocky Renquist, the actual <br />estimate of tree loss may not be known for another 2 or 3 years and <br />also the overall I ife of many trees may have been reduced. It is <br />estimated that approximately 30% of these orchards and vineyards might <br />have been destroyed. <br /> <br />. <br /> <br />. <br /> <br />Because of the freeze, sites with peaches and grapes were not heavi Iy <br />irrigated. These plants were irrigated for plant maintenance only. <br /> <br />In 1989, the average deep percolation for all 19 sites was 12.3 inches <br />(Table 2). When only the 14 surface irrigated sites are taken into <br />account, the average deep perco I at i on is 16.4 inches <Tab I e 2). The <br />average for the 5 sprinkler and microspray sites is 0.9 inches <Table <br />2). A Comparison of 5 years of deep percolation data <Table 3) shows <br />1989 data to be s light I y lower than 1986, 1987 and 1988, but <br />substantially less than 1985. The deep percolation values shown on <br />Tables 2 and 3 are average values obtained from both surface and <br />sprinkler irrigated sites. <br /> <br />In 1989, there was a large drop in deep percolation at 6 sites <11, <br />12, 14, 32, 36 and 37> but there was a I so a large increase in deep <br />percolation at 2 of the sites (27 and 29). The decrease for 1989 <br />could be attributed to reduction in deep percolation at the above 6 <br />sites. Deep percolation increased at site 27 because of change In <br />crop from the prev i ous year (a If a I fa to corn) and a I so change in farm <br />operator. <br /> <br />Previous irrigation monitoring studies in the Grand Valley by Colorado <br />State University show deep percolation to be about 8 inches for the <br />Va I ley. The SCS M&E stud i es of the past five years show deep <br />percolation to be considerably higher (Table 3). <br /> <br />The results In Table 4 show that for most sites and crops, the actual <br />deep percolation is considerably more than the acceptable deep <br />percolation for leaching based on 15 percent of actual <br />evapotransp i rat i on (ETa) va I ue. Based on past stud i es, it is assumed <br />that deep percolation of around 15 percent of ETa would be adequate to <br />keep excessive salts at a level below the root zone. With the amount <br />of data collected so far on deep percolation and soi I sal inity levels, <br />it is difficult to determine any trend. The amount of deep <br />percolation required to leach salts below the root zone can only be <br />recommended following several years of irrigation monitoring. Refer <br />to Part 2 for more details on soil salinity monitoring. <br /> <br />Of the 16 sites mon i to red in 1985, 8 of them were st i I I be i ng <br />mon i tored through 1989; 5 i tes II, 12, 14-18, and 21. However, of the <br />8 sites, only 4 sites, 11, 14, 15, and 17 sti II have the same crop as <br />1985. In the G"and Valley, fields that are in annual crops or alfalfa <br />go through a crop rotation. This therefore makes it impossible to <br />compare all individual 5ites for the different years that they have <br />been monitored. A comparison between 1985 through 1989 data is <br />possible for sites 11,14,15 and 17 only <Table 5). All other sites <br /> <br />11 <br />