Drip Irrigation Is the Only Way to Go
In the current cycle of drought years, it is a good time to review irrigation practices to determine if current systems are meeting our needs and that of the community. I heard about a report, second hand so I can’t vouch for it, that the Eastern Shore water table was something like eight feet below normal in March 2002. Even if it were only a few feet below normal, we would have to give it notice. Also, given that the drought situation has brought government to regulating water usage, it makes sense for exempt agricultural users to make an effort to look like a good citizen by reducing water consumption.
I really can’t say that drip irrigation is the only way to go for every last nurseryman, but it makes my argument easier to simply say that overhead irrigation is wrong.
At my first nursery we used overhead irrigation with water sourced from the Potomac River. With all that water rushing by it seemed logical to just crank up the diesel pump and push 500–600 gallons a minute to the field. We set up a solid set system of 5", 4" and 3" aluminum pipe with 6–foot risers and 40 gpm sprinklers. More sprinklers at lower volume would have been better but would have doubled the number of lateral pipes. I didn’t get very good advice on the system.
I can assure you that I would never do it again, with or without any outside pressure to do so. The soil was a heavy silt loam, high percentage of clay, that would become a gooey gumbo for several days after irrigation—almost impossible to work or walk in the field. The topography was relatively flat but irrigation induced erosion was a problem. The erosion messed with my pre-emergent program to the extent that weeds were an enormous problem. Surface applied fertilizer certainly washed away to some extent and roadway ruts became a constant hazard. Holes left from digging retained water for days and became a breading site for mosquitoes. Looking back, it was really not much fun being there during irrigation season. Of course it was a small operation so I couldn’t irrigate a block and work 100 acres away until the soil dried up.
When I purchased the site for Waverly Farm, I knew that the good news related to no surface water in the immediate vicinity and that we would not be able to poke a hole 50 feet in the ground to find 1200 gallons per minute. I could only assume that the vast Frederick Limestone Aquifer lying beneath would support our needs.
After many years of experience with drip irrigation, we conclude the advantages are significant:
- Water consumption with a drip system is approximately 10% that of overhead without sacrificing plant production.
- Both water and fertilizer are focused at the growing zone. To prepare our nutrient management plan, we determined that we are actually irrigating and fertilizing 32% of our total production acreage due to the zoned or banded affect of drip irrigation combined with fertigation. This clearly points out the fertilizer and water savings.
- Soil erosion from irrigation is non-existent.
- We install a valve on every tube. The cost is about $1.45 each. This allows us much flexibility in both water application and fertility rates. If for example we plant a small block in a large zone, we can focus water on the new plantings while not wasting it on more established plants nearby. Digging during any season can benefit from the ability to focus water on a single row. During a serious drought year, we needed water in March to improve digging conditions. It took about 20 minutes to get the system up and running while an overhead system might require a day or more. I can also discourage growth by not irrigating certain plants for which the market demand has slowed.
- The ability to spray, prune, stake, harvest and perform nursery tours while the irrigation is running has significant benefit.
- Weed production is significantly lower without the pooling, ponding, and small streams caused by overhead irrigation.
- Fertigation saves tremendous amounts of capital. At one point I did an analysis that more or less proved that the fertigation system saved enough capital to purchase new drip tube every 5 years while we expect to have a useful life of no less than 20 years. The cost savings relate to less costly fertilizer, no distribution equipment and no additional labor to apply the fertilizer. A further advantage of fertigation is that we can provide small amounts of fertilizer over several months thus eliminating the potential for run-off and at the same time allowing for an averaged dosage of nutrients over a broad spectrum of weather conditions.
- In a drought environment, we save 90% of the water needed and do not stir up any community controversy for our use of the water. Many of the local folks ask why we don’t irrigate when in fact we are running the system 24 hours per day, seven days per week.
- The above creates another advantage in that overhead irrigation really needs an observer during all hours of operation to find major leaks and to monitor the pumping station especially when engines are used. The non-polluting appearance of using electricity for pumping is also a good neighbor outcome.