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<br />[SOlL WATER AT FIELD CAPACITY AT PLANTING TlMEJ
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<br />I-APPLIEDWATER
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<br />Yti _ .}~, IV - CROP PRODUCTiON
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<br />Figure 1. Applied water depths and their impacts on
<br />evapotranspiration, evapotranspiration
<br />deficit, and crop production. Schemetic.
<br />
<br />line source sprinkler plot. Figure 3 utilizes data
<br />from one of the 1974 plots at Logan to show the
<br />cumulative water application pattern which had
<br />occurred by season's end.
<br />
<br />
<br />At each of the four sites (Logan, Yuma, Fort
<br />Collins, and Davis), four plots were planted in
<br />corn. Al1 four were irrigated in the same spatial
<br />pattern shown in Figure 3, but each was irrigated
<br />on a different time schedule, One of these was the
<br />control time schedule or treatment desigued to
<br />provide . sufficient water to satisfy the crop'
<br />evapotranspiration requirements fully. A fixed
<br />schedule of irrigations for each site was established
<br />to meet the criterion for local soil and climatic
<br />conditions.
<br />
<br />Since this time schedule of irrigations provi.
<br />ded the full evapotranspiration needs of the crop
<br />during the vegetative, pollination, and maturation
<br />periods, the control time schedule was desiguated
<br />III. The other three schedules differed from the
<br />control treatment in that the fixed irrigation
<br />schedule was halted, first in the vegetative period
<br />
<br />(OIl), second in the pollination period (101), and
<br />third in both (001), All plots were irrigated in the
<br />maturation period, except a few specific instances
<br />noted later.
<br />
<br />For the control schedule, the first irrigation,
<br />after moisture for germination had been assured,
<br />was applied shortly before the crop began to
<br />experience any slowing of the ETA rate below the
<br />ETM rate. Additional irrigations were then applied
<br />at regular intervals throughout the irrigation
<br />season, which stretched from the early vegetative
<br />period into the early maturation period.
<br />
<br />Generally speaking, the same quantity of
<br />water was applied on each irrigation date. It was
<br />calculated to be in excess of crop needs very close to
<br />the sprinkler line. The next few rows, e.g., rows 4,
<br />5, and 6 from the lateral, received the optimum
<br />amount, sufficient to meet all needs, but not in
<br />
<br />
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<br />30.5m
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<br />Figtlre ll. Schematic di4gram of the line .prinkler
<br />plAlt .howing wetted perimeter of each
<br />.prinkler. PlAlt wittth ovema must be
<br />greater to permit .oil water and yield
<br />measurement. in the unil'l'igated eondi-
<br />!ion, alld to provide a bonier area.
<br />
<br />4
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