Issue: April 2005
Try Easy-to-Install Drip Irrigation SystemsSee special spring soil preparation supplement below
Despite much needed moisture this winter, gardeners must still conserve water. Drip irrigation is a good start.
There are four common techniques for irrigating gardens. Sprinklers are very inefficient because wind blows much of the water away. Flooding is good for large irrigated pastures or alfalfa fields, but itís a waste in small vegetable gardens. And furrow irrigation loses a lot of water that seeps into soil away from roots.
In contrast, drip irrigation waters the base of the plant, where it filters down to roots. This reduces water loss between plants and denies water to weeds.
Drip irrigation systems often intimidate home gardeners because some require elaborate electrical timers and plumbing. Expense is also a major deterrent. However, relatively simple, inexpensive drip systems are now available at most hardware stores and can be self-installed in a few hours.
Simple systems use battery timers connected to the nearest garden faucet. Wrap Teflon tape around faucet threads to keep it from leaking.
Analog timers are inexpensive and have easy-to-use, adjustable dials to determine the days and lengths of time the system turns on and off. However, most analog timers are only good for one growing season.
More expensive digital timers last longer and are more accurate, but theyíre a little harder to program. Programming instructions come with all timers.
Connect an antisiphon device to the bottom of timers to keep water from being sucked back into the house. Brass antisiphons are better than plastic, which become brittle and often break down in sunlight. Place the antisiphon device at least six inches above the highest emitter in the garden. When the system shuts off, water will squirt out through the device.
Place a pressure regulator below the antisiphon device. Most drip irrigation systems cooperate best at pressures of 12 to 15 pounds per square inch. Water pressure in most houses is generally much higher.
Place a screen or filter below the pressure regulator, especially if the house has a well for drinking water. Clean the screen periodically to remove sand or other matter that can clog emitters.
Connect the header line to the filter and roll it out like a hose at the top of the garden. Most header lines are half-inch diameter polypropylene tubing. Cut tubing to fit the gardenís shape and put it back together with compression fittings. Buy all supplies from the same manufacturer to make sure fittings hold properly. Place a drain plug at the end of the header line to hold in water. In the fall, remove the plug and blow the water out of the tube to prevent freezing.
Drip lines are normally quarter-inch diameter tubing. To connect them to the header line, punch a hole in the header, place a barb in the hole and connect the other end of the barb to the drip line. Place a plug at the far end of the drip line to keep water from running out of there.
Drip lines have periodic laser holes or imbedded pressure-compensated emitters where the water comes out. The imbedded emitters tend to distribute water more uniformly, and they plug up less. The distance between emitters varies from 6 to 18 inches. Six-inch spacing is better for most row crops because the water pattern is more uniform. Thatís particularly good for sandy soils.
Bury the header line in the soil to keep it from breaking down in sunlight. Use coupling compression fittings to repair broken header lines and barbs to fix drip lines.back to top
Preparing Soil For Spring GardenSpecial April 2005 Supplement
(Editors Note: Following is a special, one-time supplement.)
For healthy, hardy fruits and vegetables, enrich garden soils in early spring, before planting.
The first step is a good soil analysis. Soil samples taken 6 to 8 inches deep at several locations will ensure a good representation of whatís in the garden.
Most New Mexico soils are low in organic matter. Adding compost, whether homemade or purchased, is an easy and safe way to build organic matter. However, donít spread fresh livestock manure in the garden. It can burn seedling vegetables because of its salt content and introduce weed seed and even E.coli bacteria.
Compost builds soil structure. It improves drainage in heavy clay soils and increases water holding capacity in sandy soils. It also improves soil absorption of nutrients, making them more available to plants.
Plants require 16 chemical elements to grow properly. Oxygen, hydrogen and carbon come from air and water. Soil supplies the rest. Shortages of any of the remaining 13 elements can limit crop growth.
Of the 13 elements derived from soil, plants need only three in large quantities: nitrogen, phosphorus and potassium. They can be added to soil with fertilizers. Most New Mexico soils are already high in potassium, but test soil to make sure.
Compost will supply most of the other minor elements. Compost is generally made of plant materials like coffee grounds, banana peels, citrus rinds, potato skins and apple cores. Such plant materials provide the necessary nutrients in an organic form, which are slowly released to plants throughout the season. Thatís important because most commercial fertilizers donít contain minor elements.
Commercial fertilizer bags have three numbers on them. The first stands for the percentage of nitrogen. The second is the percentage of phosphorus, written P2O5 or spelled out as phosphoric acid. The third is the percentage of potassium, written K2O.
Nitrogen is important for good vegetative growth. Shortage of nitrogen can result in a stunted yellow plant. Phosphorus improves root growth and fruit production. Shortages can result in purple coloration of older leaves, although cool weather can cause similar symptoms. Lack of potassium can slow growth, weaken stems, and burn the margins of leaves, although that could indicate salt burn.
Apply nitrogen fertilizers in split applications, particularly with crops like corn. Apply one third before planting seed. Scatter it evenly across the garden and incorporate it lightly into the soil. Nitrogen fertilizer left on top of soil will vaporize as ammonia.
Apply another third a few weeks after plants emerge, and the last third a month later. Apply the nitrogen in a band or shallow furrow four to six inches to the side of plants. Cover the fertilizer with soil and immediately irrigate the plants. That ensures a relatively even supply of nitrogen to the roots throughout the growing season.
Apply phosphorus fertilizer before planting. Incorporate it into soil where roots can reach it. Apply phosphorus-only fertilizers directly below the seed row to make it more available for plant uptake. If the fertilizer contains both phosphorus and nitrogen, spread and incorporate it into the soil. Banding such fertilizers directly below seed rows can burn developing roots when they reach the concentrated nitrogen.
If soil is low in potassium, spread potassium fertilizer and incorporate it into soil with other nutrients before planting. Like nitrogen, potassium is a salt and should not be banded directly below the seed row.back to top
For more gardening information, visit New Mexico State University's Cooperative Extension Service publications world wide web site at http://www.cahe.nmsu.edu/pubs/_h.
George W. Dickerson, Ph.D., is is a horticulturist with New Mexico State University's Cooperative Extension Service. New Mexico State University is an equal opportunity/affirmative action employer and educator.
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