The Irrigation Dating Game:
Finding the Perfect Match for Plants and Water
The purpose of this lesson is to help students understand that a farmer or rancher must take into account multiple factors when choosing an irrigation method for crops or pasture. Topography, crop selection and soil types will be compared with the three main types of irrigation: gravity flow, pressurized sprinkler and micro-irrigation.
The students will:
- Describe and simulate the three main types of irrigation systems.
- Describe several subtypes of each of the three main irrigation system types.
- Explore the influence slope, crop and soil type variations on the choice of irrigation systems.
Science - Hypothesizing, critical thinking, analyzing, comparing similarities and differences, describing, demonstrating, observing, listening, recording, discussing
English/Language Arts: - Reading, writing (technical), speaking
Performing Arts: - Creating, building
History/Social Science/Geography - Comparing past to present, studying geographical and topographical regions, weighing science against social perceptions, economics
Mathematics - measuring, subtracting, adding
In 1940 the average farmer in the United States could produce enough food for 19 people. Today, an American farmer can produce enough food to feed 129 people -- 101 in the United States and 28 abroad. Technological advances have increased the productivity of farmers, particularly by improving their ability to provide water to their crops through irrigation. Irrigation is defined as the managed application of water to soil for the purpose of increasing crop production.
Irrigated agriculture has helped American farmers produce the most abundant and diverse supply of food, fiber and foliage products in the world. Irrigation plays an especially important role in the Western United States where growing seasons are longer but there is not enough rainfall to supply an optimum amount of water to commercial crops. California alone produces over 250 agricultural commodities, most of which could not be grown there without irrigation.
The following AgriWater information and activities will focus on the three main types of irrigation - surface gravity flow, pressurized sprinkler, and micro-irrigation. In order to select the appropriate type of irrigation, the farmer must make informed decisions. Water availability, economics, soil types and plant biology factors must all be studied before choosing an irrigation technique. Some of the major considerations for the farmer or rancher include:
The complexity of choosing an appropriate irrigation system and utilizing the available water productively has helped to insure that good farmers are true water managers, very aware of conservation principles. It is in their own best economic interest to use water wisely.
- proximity of the field or pasture to a water source
- adequate distribution system to the field (pumps, canals or pipes)
- amount of water required by selected crop
- quality of available water
- cost of water
- topography of the land
- soil type
- annual precipitation
- cost of irrigation supplies
- availability of labor to set-up and maintain irrigation system
- fertilization methods
- methods for recycling or handling excess irrigation water
Basin irrigation, pressurized sprinkle irrigation, micro-irrigation, soil type, drainage, water holding capacity, saturation, runoff, water conservation.
Activity 1: Comparing the water holding capacity and speed of water saturation:
Different soils hold different amounts of water in the spaces between the soil particles. The amount of moisture a soil can retain per unit of soil volume is called its holding capacity. Holding capacity determines the quantity of water an irrigator must apply to a particular field and the frequency of the water application. In this lesson students will observe and demonstrate the different water holding capacities of sand, silt and clay soils.
Sand, silt and clay are distinguished physically by the size of the particles: sand having the largest and hardest particles, silt hav