Horticulture Principles and Practices

FIGURE 4 Fertilizer injector
plumbed into drip irrigation
system in high tunnel. (Photo
courtesy of Catie Rasmussen)
(This item omitted from WebBook edition)
ADVANTAGES OF DRIP IRRIGATION
1. Smaller water sources can be used, because trickle irrigation may require less
than half of the water needed for sprinkler irrigation.
2. Lower operating pressures mean reduced energy costs for pumping.
3. High levels of water use efficiency are achieved because plants can be supplied
with more precise amounts of water.
4. Disease pressure may be less because plant foliage remains dry.
5. Labor and operating costs are generally less, and extensive automation is possible.
6. Water applications are made directly to the plant root zone. No applications are
made between rows or other non-productive areas, resulting in better weed
control and significant water savings.
7. Field operations, such as harvesting, can continue during irrigation because the
areas between rows remain dry.
8. Fertilizers can be applied efficiently through the drip system.
9. Irrigation can be done under a wide range of field conditions.
10. Compared to sprinkler irrigation, soil erosion and nutrient leaching can be reduced.
DISADVANTAGES AND LIMITATIONS OF DRIP IRRIGATION
1. Initial investment costs per acre may be more than other irrigation options.
2. Management requirements are somewhat higher. Delaying critical operation
decisions may cause irreversible damage to crops.
3. Frost protection is not possible with drip systems; if this is needed, sprinkler
systems are necessary.
4. Rodent, insect, and human damage to drip lines are potential sources of leaks.
5. Water filtration is necessary to prevent clogging of the small openings in the emitters.
6. Compared to sprinkler irrigation, water distribution in the soil is restricted.
LOW TUNNELS
Low tunnels have been used in field production in North America for the last 50
years. Use of low tunnels (24 to 36 wide by 18 to 30 tall) for vegetable crops
helps to warm the soil, maintain higher air temperatures under the tunnel, maintain
higher levels of soil moisture, reduce plant stress from wind, reduce/eliminate insect
618 Chapter 20 Growing Vegetables Outdoors