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<br />,,) <br />L") <br />, 'oJ <br />..... <br /> <br />"EFFECTS OF ONFARM WATER MANAGEMENT". Note that these factors are <br />used on the data sheets as salt tons/ acre inch on the data sheets for 1990, 1991. <br />1992, and 1993. These numbers have been generated by USSR and USDA for the <br />different areas of the Grand Valley based on measured salt contributions. <br /> <br />c..) <br /> <br />The total salt contribution from each field, where data was obtained, has been <br />calculated using the number of acres under surge, the acre inch reduction of deep <br />percolation due to the use of surge irrigation, and the tons of salt produced per <br />acre inch of deep percolation. These numbers and the total are shown in the right <br />column of the data sheets. <br /> <br />Additional, incalculable, salinity benefits can be expected to have occurred in that <br />not all irrigation events on all farms were evaluated each year. <br /> <br />DEEP PERCOLATION REDUCTION: <br /> <br />The amount of deep percolation in acre-inches by conventional and surge irrigation, <br />divided by the acres in each for all years, indicates a deep percolation savings as a <br />result of surge irrigation, as shown below: <br /> <br />comparison of deep percolation, by system, in acre inches per <br />acre. <br /> <br />Year <br />1990 <br />1991 <br />1992 <br />1993 <br /> <br />conventional <br />5.6 <br />4.6 <br />1.1 <br />0.7 <br /> <br />Suroe <br />1.5 <br />1.5 <br />0.4 <br />0.03 <br /> <br />Several reasons may exist for the declining deep percolation as shown in the above <br />data: <br /> <br />11 Winter moisture and spring rains may have left the soil in the fields in a <br />condition conducive to packing which increased the soil bulk density. <br />Increased bulk density reduces infiltration rates. Weather conditions during <br />the corn planting seasons of 1992 and 1993 were such that they inhibited <br />work in corn fields. This reduced tillage lowered or minimized the loss of <br />stored soil moisture which reduced the amount of early irrigation. <br /> <br />2) The farmers who requested surge units at the start of the program were <br />either the more innovative farmers or the ones with the most serious <br />irrigation problems. <br /> <br />31 The last group of farmers to request surge units were more involved with <br />orchard crops; generally, orchard fields have shorter furrow rows, are easier <br />to manage under conventional irrigation systems and may show less <br />advantage to the surge system. This is supported by the data from field <br /> <br />6 <br />