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<br />o <br />~ <br />c"? <br />C., <br /> <br />. <br /> <br />. <br /> <br />'- <br /> <br />The variation in efficiencies for individual irrigations ranged from <br />4% to 89% for surface irrigation and from 36% to about 100% for <br />sprinklers (Refer to Appendix A for more detai Is on individual <br />irrigations). The sites with poor irrigation efficiencies generally <br />were irrigated sooner and longer than was needed. Improper schedul ing <br />and long set times caused excessive deep percolation on some of the <br />sites. Irrigation efficiencies can be improved at some sites with <br />better irrigation scheduling and the adjusting of set times or inflow <br />rates. <br /> <br />The results for each crop is discussed below: <br /> <br />Alfalfa: There were 9 sites monitored in 1989, of which sites 6 were <br />under surface irrigation and 3 under sideroll sprinkler system (Table <br />2). Of the 9 sites, 5 were the same sites as in 1988, 1 was a new <br />site added this year, 3 sites - 16, 21 and 33 switched to alfalfa <br />after having different crops for a few years. Total acreage for the <br />monitored alfalfa sites was 253 acres, or 0.9 percent of the 29,500 <br />acres I n the Grand Va II ey <Tab I e 7). <br /> <br />I,n 1989, there was an average of 9.9 inches of deep perco I at i on from <br />the alfalfa sites <Table 2) which IS considerably less than in 1988 <br /><15.5 inches). The average deep perco I ati on of 9.9 inches for the <br />alfalfa sites is about 20% below the average deep percolation for al I <br />19 sites (12.3 inches) monitored <Table 2). When only surface <br />irrigated sites is taken into consideration the average deep <br />percolation is 14.8 inches <Table 8). Of the 6 surface irrigated <br />sites, 5 of them had deep percolation over 100% of the average (9.9 <br />inches) for all alfalfa sites <Table 8). Only site 16 had below <br />average deep percolation with 3.5 inches, which is about 35% of the <br />average for al I alfalfa sites. This was a newly seeded alfalfa field. <br />At this site, only the first 2 irrigations had deep percolation and <br />during later irrigations the amount of water applied was never <br />adequate to meet the needs of the plants (Refer to Appendix A for <br />individual irrigations). There was no visible signs of plant stress <br />during the growing season. <br /> <br />AI I 3 siderol I sprinkler sites had no deep percolation, although in <br />1988, site 36 had about 17 inches of deep percolation. The amount of <br />water app lied was never adequate for p I ant needs (Refer to Append i x A <br />for individual site data). <br /> <br />Deep percolation losses on alfalfa sites seem to be fairly uniform <br />throughout the irrigation season unlike sites with annual crops where <br />most of the deep percolation occur during the first irrigation (Table <br />8). On surface irrigated alfalfa sites, approximately 25% of deep <br />percolation occur by the first two irrigations (Table 8), Site 16 was <br />'n corn in 1988 and seeded to alfalfa in 1989. This site had 100% of <br />deep percolation losses by the second irrigation. Refer to Appendix A <br />for more deta i Is. <br /> <br />Towards the middle of the season, al I the operators received <br />individual irrigation summaries and soil moisture deficit data every <br />2 to 3 weeks to help them with their water management decisions. <br /> <br />16 <br />