Irrigation Home Study Course Summary

1. Why Manage Water for Irrigation: This short chapter provides goals of irrigation water management and consequences of failing to employ irrigation scheduling principles. Information and equipment needed to accurately schedule irrigations is summarized in 5 concise components.

2. Physical Properties of Soils: Properties of soils that influence crop growth and soil water holding characteristics are discussed in this chapter. Soil texture determination, structure and classification are presented to help understand soil survey reports.

3. Soil Water: This chapter discusses the soil’s ability to store and transmit water. The Examples of how water movement through soil is affected by soil texture are illustrated.

4. Measuring Soil Water: This chapter covers various methods used by producers to measure soil water content starting with electrical resistance blocks and ending with neutron probes. Procedures for locating monitoring sites are discussed for furrow and sprinkler irrigation systems.

5. Nitrate Movement and Loss Under Irrigated Crop Production: Failing to manage irrigation water applications has led to increased groundwater nitrate levels in irrigated areas of the U.S. This chapter discusses how depth to groundwater and type of overlying soils impact downward movement of nitrates. A description of the nitrate leaching process is presented using two examples. The chapter ends with a discussion of leaching loss research conducted in Nebraska.

6. Crop Water Use: This chapter begins by defining crop water use and its components, evaporation and transpiration. Factors affecting crop water use rates such as soil residue cover, climate, leaf area, plant population, relative maturity range, and soil water levels are discussed in detail based on Nebraska research results. Procedures used to estimate crop water use from weather data and how estimates should be used round out the chapter.

7. Flow Measurement and Basic Water Calculations: Accurate flow rate estimates play a key role in irrigation scheduling procedures. This chapter discusses different flow measurement technologies such as impeller and ultrasonic meters. With flow rate measurements recorded, basic water application calculations are presented for furrow and sprinkler irrigation systems.

8. Irrigation Efficiencies: This chapter presents factors that impact irrigation water application efficiency for furrow and sprinkler irrigation systems. Comparison of the gross water applied discussed in Chapter 7 with field based changes in soil water content discussed in Chapter 4 is used to develop estimates of irrigation efficiency.

9. Soil Water Balance: This chapter discusses using the Checkbook Method of irrigation scheduling. Procedures for maintaining a soil water reservoir checkbook account are discussed. Irrigation efficiency, effective rainfall, crop water use and soil water content information are used to estimate a soil water balance.

10. Scheduling Irrigations: Irrigation scheduling is the process of applying the correct amount of water at the right time. This chapter presents examples of how to implement no-later-than and no-sooner-than irrigation management schemes. An example for determining the last irrigation event is presented and some example worksheets are provided at the end of the chapter.

11. Furrow Irrigation Management: This chapter discusses different methods of furrow irrigation and how to evaluate and adjust stream size and set time to achieve the most efficient water applications. Conventional gated pipe and surge irrigation system operation examples are presented with graphic illustrations.

12. Sprinkler Irrigation Basics: Beginning with irrigated area calculations, this chapter discusses how to estimate flow rate needs based on long term crop water use rates, soils, and precipitation information. Peak water application rates and system revolution time are presented to help establish system management schemes. Procedures for measuring gross water applied and how to match sprinkler packages with field conditions are discussed in relation to a zero runoff rule.

13. Energy Costs for Irrigation Pumping: The cost of pumping irrigation water is based on fuel cost, the efficiency of the pumping plant, the volume of water pumped and the total head (lift plus pressure). This chapter discusses how to collect information needed to estimate pumping plant performance and how to calculate equivalent costs of different fuel types.

University of Nebraska Cooperative Extension

Irrigation Management Home Study Course