Experiments were conducted with 180 m long T-tape and Agrifim emitter lateral lines in the laboratory and field to determine the effects of water temperature and sediment concentration on the hydraulics of drip irrigation laterals. The flow regime was laminar through the T-tape emitter and turbulent through the Agrifim emitter. Water temperature decreased along the lateral line in the laboratory where the inlet water temperature was higher than ambient air. In contrast, temperatures increased along a lateral line exposed to the sun in the field with an inlet temperature lower or slightly higher than that of air. The rate of increase or decrease was more pronounced towards the end of the line. The effect of temperature was highly significant on emitter flow rates obtained for a T-tape emitter as opposed to those recorded for the Agrifim emitter in the laboratory; however, the increase of emitter flow rates due to temperature was reduced by plugging in the field. Discharges of T-tape emitters were dominated by the hydraulic pressure for the first half of the line with the water temperature being more important for the second half of the line in both the laboratory and field. Measured discharges of Agrifim emitters were dominated by the hydraulic pressure for the entire lateral length especially in the laboratory. The Darcy-Weisbach friction factor, as opposed to the Blasius friction factor, is recommended for design because it accounts for the wall roughness of the pipe. The Hazen-Williams roughness coefficient was related to Reynolds number to improve the drip system design. Total friction losses, as a result of water viscosity changes and lateral discharge variations due to temperature, increased significantly for the T-tape emitter lateral in the laboratory and field for different inlet water temperatures and inlet-outlet temperature variations. In contrast, total friction losses decreased for the Agrifim emitter lateral primarily because of water viscosity changes with temperature. The sediment concentration along an Agrifim emitter lateral in the laboratory decreased sharply in the second half of the line when the flow velocity dropped below 0.29 ms⁻¹ . Also friction losses increased for an Agrifim emitter lateral in the laboratory as the inlet concentration increased from 200 to 650 mg/l.

This item was digitized as part of the Million Books Project led by Carnegie Mellon University and supported by grants from the National Science Foundation (NSF). Cornell University coordinated the participation of land-grant and agricultural libraries in providing historical agricultural information for the digitization project; the University of Arizona Libraries, the College of Agriculture and Life Sciences, and the Office of Arid Lands Studies collaborated in the selection and provision of material for the digitization project.

This item was digitized as part of the Million Books Project led by Carnegie Mellon University and supported by grants from the National Science Foundation (NSF). Cornell University coordinated the participation of land-grant and agricultural libraries in providing historical agricultural information for the digitization project; the University of Arizona Libraries, the College of Agriculture and Life Sciences, and the Office of Arid Lands Studies collaborated in the selection and provision of material for the digitization project.

Upland cotton lint yield response to several soil moisture depletion levels was measured in 1997 and 1998. In 1997, four Upland cotton varieties including DP 5415, DP 33B, DP 5816, and STV 474 were tested. However because of a nonsignificant variety difference in the 1997 test, the 1998 test was planted to a single variety (DP 33B). In 1997 and 1998, depletion of plant available soil water (PAW) irrigation treatments consisted of 35%, 50%, 65%, and 80%. In 1997, all PAW depletion treatments were significantly different with the 35% PAW treatment resulting in the highest average lint yield of 1880 lbs. lint/acre. The 50%, 65%, and 80% PAW treatments resulted in 1410, 1123, and 248 lbs. lint/acre respectively. There was no significant (P<0.05) difference between varieties within all PAW treatments in 1997. In 1998, all PAW depletion treatments again were significantly different with the 35% PAW treatment resulting in the highest average lint yield of 1658 lbs. lint/acre. The 50%, 65%, and 80% PAW treatments resulted in 1534, 1396, and 641 lbs. lint/acre respectively.

Another year of data was collected to determine the effects of high frequency irrigation on irrigation uniformity in cotton production. A field located at the Marana Agricultural Center was split into two treatments. Treatment one was irrigated at approximately 35% depletion of available water in the plant rootzone. Treatment two was irrigated at approximately 65% depletion in the crop rootzone. Increased frequency of irrigation has shown improved yields in many cotton studies. However, these more frequent and lighter irrigation applications may cause problems with irrigation uniformity. Frequent rains during critical time periods made it difficult to ascertain the impact of the irrigation schedule on uniformity. However, the less frequent, heavier application rate did result in a more uniform irrigation.

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