Exam 1 Soils 456.   Take home test. Due in class on March 10 Bring hard copy and floppy disk. No class on March 8 to work on examination.

1. Explain under what conditions you would use sprinkler vs a flood vs a drip irrigation system to irrigate a soccer field in Las Cruces. Explain the advantages and disadvantages of each type of system and explain the reasoning behind your final choice of irrigation system.  The field is located on the east side of Burns Lake. Please look up the soil type and incorporate that knowledge in your answer. Points 15

2. The feel method is used to determine the soil type and the moisture content for scheduling when to irrigate. A technician went to the Chile field located at a field located 5 miles north of Las Cruces and reported to you that he found the following information.

Sample depth   1ft     soil stays in a ball when squeezed and makes a strong ribbon and does not feel gritty or very smooth

Sample depth    2 ft    soil stays in a ball when squeezed and does not form a ribbon. The second foot shows subsurface horizon development with a gypsum layer

Sample depth 3 ft      soil does not stays in a ball when squeezed and does not form a ribbon, but the soil moisture content is the correct amount for analysis.

What are the soil textures with depth and what is the total available water holding capacity of the 3 ft root zone. Use the Saxton  calculator  to calculate  the water-holding capacity of different textured soils. Show all calculations. Also what is the soil order?  Show all calculations.  Points 15

3. The water use of a lawn in April is .2 inches per day.  A sprinkler irrigation system with an application rate of 0.45 inch /hr was turned on for 1.5 hrs every three days  to irrigated a lawn located at a residence on Telsore Blvd. The front lawn had a slope of 15 percent and after the system ran for 40 minutes, runoff started to occur. The soil was a clay loam soil with a saturated hydrologic conductivity of 0.05 inch/hr.  Explain physically what was happing to the water applied by the sprinkler system and why the runoff started to occur after 40 minutes but not before that time.  A water samples was take and the soil was high in sodium with an Sodium Absorption Ratio of  7 .Explain what impact a high SAR had on the runoff problem and what you would do to fix the runoff problem?  Show all calculations.  Points 15

4. If a field that has a  loam soil was planted to cotton on May 1 2001 at the Leyendecker science center.  On what dates should the field be irrigated to prevent any reduction in yield due to moisture stress. The irrigation system is furrow and the runs are short so a flow of 1800gpm is applied to the 6 ac field and the time to irrigate the field is 5 hr. Please attach the excel spreadsheet to show your calculations. What is the irrigation efficiency of the furrow system? Show calculations for irrigation efficiency.  Points 25

5. The city of Alamogordo gets its water from a Lake in the mountains with the surface of the lake located at 4720ft. The bottom of the lake is at 4600 ft. A pipe runs from the bottom of the lake to the city distribution site at 4220 ft. What is the water pressure at the distribution site? If you have a house that is located a mile away at an elevation of 4500ft and the friction loss is ignored what is the pressure at your water meter.  Points 10

6. A cotton field is flood irrigated with a high flow turnout that discharged 6750 gmp into the field. The boarder in the field is 600 ft long and 120 ft wide. The irrigation-scheduling model determined that a irrigation was due on May 20 and a 3.5 inch irrigation was need to fill the root zone which would result in 2.8 inches of water being stored in the root zone. The farmer tells the irrigator to go and turn water into the field until the water reaches 75% of the way to the end of the field and then shut the water off. The irrigator does this and reports to the farmer that it took 30 minutes to irrigate that boarder. The field contains 6 boarders and the irrigator was through irrigating after 3 hr.

What was the depth of water the irrigator applied to the field? What was the target efficiency and what was the final irrigation efficiency that the farmer calculated that occurred using the rule of thumb to shut the water off when it reaches ¾ of the length of the field and let it cost the rest of the way.. Point 15

7. Explain the different type of irrigation scheduling methods and the advantages and disadvantages of each and which method you would use to schedule irrigation for a large park. There were eight method presented at the Chile conference talk by Dr. Sammis  Points 20