Introduction

1. Dramatic increases in irrigated land motivated by desire to stabilize yields and ensure against diseases of drought.

2. In 17 western states, about 26% more land is being irrigated since 1974 census.

3. About 42% of irrigated land is in the five states that have primarily warm temperate climates.

4. 28% watered by sprinkler equipment.

5. 15% gravity irrigated (underground pipes).

6. Remaining is leveled land.

7. Since 1949 - a 450% increase in irrigation in southern Great Plains.

8. Trend not limited to arid regions, more humid regions in same period increased 335%.

9. Most extensive irrigated areas:

• North America, 23 million ha
• Near East, 18 million ha
• Southern Europe, 12 million ha

1. Waters of Colorado and Rio Grande almost fully used and litigation over the allocation of remaining waters and salinity a national concern.

2. Ground water level is falling to such an extent as to threaten long-continued use at present rates.

3. Irrigation development in western U. S. approaching the limits of available water supplies.

4. Competitive demands for water for urban uses, industry and recreation increasing.

5. Future development of energy resources in western U. S. could also divert large quantities of water away from irrigation.

Changes in Methods of Irrigation

1. Manpower situation changing in two major ways:

• Need for technical skills for designing, installing, and maintaining systems (consultants)
• Decreasing needs for technical skills in carrying out irrigation practices (simple)

1. Irrigation in furrows, borders or basins still most extensively used method of irrigation.

2. Head gates are being constructed to automatically raise or lower with time clock controls, so water will move from one location to another at prescribed intervals.

3. Difficulties in obtaining reliable labor and high water application efficiencies ;make the automated grated pipe and center pivot system attractive.

4. As fuel costs increase, the high pressure center pivot may become less attractive.

Cropping Systems

1. In western U. S., the general trend toward specialization (monoculture).

2. A flexible cropping system used with alfalfa.

• Because of wilt and other disease, it is grown 3-5 years, followed by corn or potatoes.
• A nurse crop (barley) used to reestablish alfalfa.

4. Multiple cropping is primarily limited to the warm temperate climatic zone.

• Common combination is wheat in winter and corn or sorghum in summer

• Ca grows 200 different crops

• Salt-tolerant crops such as barley, alfalfa, sugar beets, and cotton are favored

• This is all on irrigated land

1. Fertilizers.

• Fertilizers can be fairly accurately estimated based on soil tests and knowledge of crop requirements.
• Supplemental N is side dressed or added to irrigation waters (especially if sprinkler systems used)
• Zn, Mn and B often mixed with fertilizer, better results with foliage applications (added to sprinkler at end of application)

• Carefully selected - many varieties have limited area of adaptation/use local test data

• Use higher populations with adequate water and high soil fertility

• Weed seeds often brought in or scattered in irrigation water (screen or filter water)
• Herbicides extensively used in irrigated farming
• Herbicides must be compatible with current and succeeding crops
• Cultivations avoided because of soil compaction and cost

• Pests carry diseases and feed directly on crop

1. Salt problems.

• Effect crop yields on 25% of irrigated land in the 17 western states
• No general solutions have been found - problem for future may be disposal of salts in drainage waters

• More than half of all irrigated farms suffer reduced yields from lack of skilled management of irrigation waters
• Not properly timed, water application efficiencies often as low as 30-50%

• Most effective irrigations applied at mid to late boot stage and at heading
• Two irrigations properly timed worth four irrigations

• Often lack capital for nutrients or are not motivated toward achieving high production levels

• Crusting
• Compaction
• Residue management

1. Agricultural research.

2. Knowledge of soils and plant nutrition.

3. New chemicals and practices to control weeds, insects, and disease.

4. Development and improvement of all types of farm machinery.

5. Specialized harvesting equipment. you

6. Adoption of new mechanical equipment has been encouraged by shortages and higher costs of farm labor.

7. Agricultural extension program.

8. Soil conservation service.

9. Farm planning (emphasizing uniqueness of each farm).

10. Farm support program.

11. The farmer is key to development without his cooperation