Evaluation of User Friendly Drip Irrigation/Mulch Systems for Urban and Small Farm Specialty Crop Production (2001-2004)

Of the 14 sites selected in 2001/2002, only one cooperator dropped out of the program after the first year. Composite soil samples (6- to 8-inch depth) were taken from each site each year and sent to the soils lab at New Mexico State University for analysis. Fertilizer applications were based on these results. Irrigation water from each site was analyzed the first year to determine salt content.

Of the 13 sites that were monitored over the entire three years, two were run by Non-Master Gardeners, two by county agents (herb projects), one by the researcher, and the rest by Master Gardeners. Master Gardeners were heavily involved with the herb project in Santa Fe and to a lesser extent in Taos.

All projects were divided up into two equal mirror-image plots. An organic mulch was applied to one plot in each project after plants had emerged except Edgewood where it was applied at planting. Mulches varied by site and included straw, alfalfa, grass hay, compost, or newspaper. The second plot served as a "check" or "control" with no mulch. Both plots, at any particular location, contained the same varieties of vegetables, herbs or cut flowers. Water sources were either private wells or city water. Water pressures varied from 28 psi (Cerro) to 98 psi (Los Alamos Community Garden).

Two identical drip system plots were set up at each site. Drip lines and types of battery timers varied with location. During the second year, a digital timer was used for one plot and an analog timer was used for the second plot at each location. During the third year, cooperators were allowed to use whichever timers they preferred from the previous years. The only exceptions were at Cerro, Taos and Santa Fe, where the same type of timer was used for both plots.

Each irrigation system consisted of a battery timer, antisiphon device (brass), pressure regulator (20 psi), "Y"-shaped screen filter, header line (1/2-inch black polypropylene) and drip line. After installation, each system was turned on for 15 minutes to calibrate the drip lines. Three rectangular shallow pans were placed under individual emitters or sections of soaker hose at random locations to collect water. The water was measured to determine the total output for each system.

Initially both systems at any particular site were set to come on for the same period of time up until the mulch was applied. The time of day each meter came on varied so meters would not compete with each other. After application of the mulch, the mulch plot was usually programmed to come on about half as often as the check plot up until frost. The exact intervals varied with location and time of year.

Most cooperators planted mixed vegetables in their plots. Herb gardens were planted at both the Santa Fe and Taos County Extension office grounds. Planting generally began in early April in Las Cruces and ended in early to mid-June in Cerro. All plots were maintained by the cooperators throughout the growing season, including weeding, insect control, and harvesting. Each project was visited by the researcher every two to three weeks during the growing season. Logs (calendars) were kept by the cooperators on most activities in the garden, including adjustment of timers and rain records. Logs were collected at the end of the season to determine water application amounts for each plot, rainfall amounts and weeding activities.

1. DIG Model 7010
2. Nelson Easy-Set 3
3. Orbit Model 62015/62415
4. Orbit Model 62001/62401
5. Gilmore Model 9400

The DIG meter was immediately eliminated since it would not completely shut off. The other four were installed randomly at the various locations throughout the state. After approximately a month, the Easy-Set 3 meters were replaced by Gilmore meters due to a number of malfunctions. During the second year, a Raindrip Model R672C was added to the mix.

Each cooperator was assigned one set of meters (same model) to evaluate the first year. Initially, the meters were installed and programmed by the researcher. Cooperators, however, were given written directions for the meters and were asked to adjust them when necessary. In September, cooperators were sent directions to cut back the irrigation days by reprogramming their meters. Two weeks later the meters were checked by the researcher to determine if the meters were programmed correctly. An evaluation form was sent out at the end of the season to each cooperator to list the pros and cons of their assigned meters. Cooperators were asked to consider "ease of use," "reliability," and "durability" of the meters.

The second year, cooperators were allowed to keep one of the meters from the previous year. The other meter was kept as a spare. Each was given a new meter to evaluate. Depending on the meter from the previous year, the new meter was either an analog or digital meter so that the cooperator had one of each. Both were evaluated at the end of the season using the above evaluation criteria.

During the third year, cooperators were allowed to select any of the meters they had evaluated in the previous years. Inherently it was a judgment call indicating which meter they felt was best.

1. Dura-Flo Jr. 1/4-inch dripper line (6-inch emitter spacing)
2. Dura-Flo Jr. 1/4-inch dripper line (12-inch emitter spacing)
3. 5/8-inch soaker hose

Each cooperator was randomly assigned one of the above types of drip line and was asked to evaluate the pros and cons of the line (same evaluation form as above). Cooperators were also asked how well the drip lines worked in combination with the mulch in conserving water. Three of the four cooperators assigned the 12-inch emitter spacing drip line were changed over to the 6-inch emitter spacing drip line during the second year, as well as one of the soaker line cooperators.

The soil samples were allowed to air dry in a garage for 2-3 weeks. They were then sifted through a kitchen colander to remove rocks and other larger debris. A 1/3-pound sample was placed in a plastic cup. Distilled water was added and stirred into the sample to make a saturated paste. The sample was then allowed to set for a few minutes. Each sample was then evaluated for total soluble salt content (g/l) using a PET 2000 Dual Purpose E.C. meter. Two readings were made for each sample and averaged.

In 2004, 24 Watermark soil moisture sensors were used in each herb experiment in Santa Fe and Taos. Sensors were soaked in water for eight hours, dried and were soaked again for eight hours. Two holes (6 and 12 inches deep) were drilled into the soil around select herbs (Echinacea, Peppermint, Mother of Thyme, Dwarf Curry Plant, Munstead Lavender and Winter Savory) with a one-inch diameter auger in each of the treatment plots (check and mulch). Holes were approximately 4-6 inches from the base of plants. Holes were filled with water and allowed to drain. The sensors were then placed in each hole and covered with a slurry of mud made from the same holes. The lines to the sensors were tied to rebar and readings (centibars) were collected throughout the season.

The test consisted of 10 questions that were either "fill-in-the-blank" or multiple choice (more than one correct answer was possible). The questions covered water, salts, nutrients and diseases affected by water. The test was administered to both Master Gardener trainees and veteran Master Gardeners. The test was administered annually at all Master Gardener programs for three years.

The amount of water applied to the check plots in 2002 (tables 2 and 3) varied from 2.2 acre-feet (Los Alamos locations 3 and 5) to 10.1 acre-feet (Bosque). The mulch plots varied from 1.6 acre-feet (Los Alamos location 5) to 7.0 acre-feet (Bosque). Water savings as a result of using mulches ranged from 7.3 percent (Los Alamos location 3) to 50.8 percent (Albuq./San Pedro). The average water savings using the mulches was 26.3 percent (did not include the Albuq./Heights location). Greater water use tended to be associated with use of soaker hoses and longer growing seasons. One exception was in Cerro, where the system was left on most of the day

The amount of water applied to the check plots in 2003 varied from 1.3 acre-feet (Cerro) to 26.9 acre-feet (Bosque, tables 2 and 3). The mulch plots varied from 1.0 acre-feet (Cerro) to 20.1 acre-feet (Bosque). Water savings, as a result of using the mulch, ranged from 18.2 percent (Santa Fe) to 53.8 percent (Las Cruces). The average water savings using the mulches was 31.3 percent (excludes Bosque). The heavy water applications at Bosque were due to new soaker hoses that had no water reduction washers (pressure reducers) in the female ends of the hoses. The water tended to go straight down through the loose soil that made up the beds and was not noted by either the researcher or cooperator. The older hoses at the same site (second figure) tended to put out less water due to salt accumulation imbedded in the hoses from the previous year which restricted, water flow.

The amount of water applied to the check plots in 2004 varied from 0.9 acre-feet (Cerro) to 8.5 acre-feet (Albuq./San Pedro, tables 2 and 3). The mulch plots varied from 0.8 acre-feet (Cerro) to 6.6 acre-feet (Albuq./San Pedro). Water savings as a result of using the mulch ranged from 14.2 percent (Rio Rancho) to 51.4 percent (Bosque). The average water savings using the mulches was 29.3 percent (excludes Los Alamos location 4 and Belen).

Of the 12 original sites that participated in the three-year project (excludes Albuq./Heights), only two sites showed no improvement in water savings over the three-year period (Albuq./San Pedro and Los Alamos location 4) when comparing check plot to check plot or mulch plot to mulch plot at each site. Reduction in water use over the three-year period at the other sites varied from 31.2 percent (check) and 33.3 percent (mulch) at Santa Fe to 84.4 percent (check) to 84.3 percent (mulch) at Cerro. Most of this improvement was associated with experience gained by the cooperators over the three-year period in programming their timers to deliver the optimum amount of water needed by their plants at various times during the growing season.

Rainfall varied from 0 inches (four sites) in 2003 to 7.9 inches (Edgewood) in 2004. 2003 tended to be the driest year (2.0 inches average across all sites), while 2004 was the wettest (4.5 inches average). The dry, hot weather of 2003 was very detrimental to crop growth at most locations during the year.

The four remaining timers (two analog and two digital) were evaluated each year for "reliability" and ease of understanding of the "instructions" by the cooperators. Cooperators only evaluated the timers they were assigned. Evaluations for each timer were combined and averaged for the three-year period and then compared (table 4).

The analog timers tended to be easier to understand in terms of instructions, since only two rotary dials needed to be adjusted to set the program. One dial set the "watering interval" or "frequency" and the other set the "watering duration." Depending on the timer, intervals varied from "once an hour" to "once a week." Assuming the "once-an-hour" option was chosen, there was no way to turn the timer off at night. Durations varied from one minute to two hours.

The digital timers tended to be harder to understand in terms of instructions, particularly the Gilmore timer. The Orbit 62001 was somewhat easier, particularly after cooperators became more familiar with it. The digital timers were a little more flexible in terms of watering intervals. The timer could be programmed to come on once every day, on any particular day or days of the week, every second or third day of the week. There were four separate program options, so the timer could be programmed to turn on at four separate times during the day to eliminate any excessive watering at night.

The digital timers were also a lot more flexible in terms of watering duration. The timers were not limited to preset times on a dial. Since the timers were set in increments of one-minute digits, the timer could be set to come on for 7, 8, 13 or even 61 minutes. The maximum time for the Orbit 62001 model was up to 360 minutes.

Before setting an irrigation program for a digital timer, a "reference" clock had to be set with the present time of day and day of the week. The program would then refer back to this clock when it was scheduled to engage. The reference time for each analog timer was determined at the time of day it was originally set. For example, if the cooperator wanted the timer to begin irrigating at 4 a.m. every 24 hours, the cooperator would have to physically set the program at 4 a.m. the first time. The program would not engage until 24 hours later at 4 a.m. This tended to be a nuisance if the program had to be changed very often during the growing season

Both analog timers were relatively cheap compared to the digital timers.

However, the analog timers, particularly the Raindrip 672C timer, tended to fail more times than the digital (Gilmore) timers. The Orbit 62001 Digital timer was the most expensive timer but was also the most reliable. Not one of these timers failed over the three-year period.

The Dura-Flo Jr. 1/4-inch dripper line (6-inch emitter spacing) was rated by cooperators as good to excellent in terms of reliability. It was rated as the best line for vegetable production due to its uniform water distribution pattern. The water patterns generally merged with each other after only one hour of water application. During the third year, however, the emitters at the ends of the lines started to clog up with salt. Depending on water quality, the lifetime of this type of emitter line is probably two to three years.

Cooperators rated the 5/8-inch soaker hose as good to excellent in terms of reliability. The hose was excellent for germinating seed because the water distribution pattern was a solid line as soon as water was applied. At the beginning of the season, water could be applied for a few moments several times a day to keep seeds wet, using limited amounts of water. Amounts could be increased over time as plants grew. This was not possible with the 6-inch spaced emitter, since it took at least an hour for the water patterns to merge.

At the herb plots in both Santa Fe and Taos in 2003, sensors were placed near established Lemon Balm plants and New French Lavender plants in both the check and mulch plots. Over the summer, at both locations in both plots, the sensors in the Lemon Balm plots always indicated less soil-water than in the French Lavender plots, indicating more water use near the Lemon Balm plants.

In 2004, moisture readings (centibars) for all moisture probes at both herb project locations in Taos and Santa Fe were generally taken at least once a week throughout the growing season. Plots were irrigated when at least two of the probes reached 20 to 30 centibars. Moisture readings for each herb depth and mulch treatment were averaged across the entire season. Echinacea (28 centibars) and peppermint (22) tended to use more water than other herbs in Taos, while peppermint (28), Winter Savory (26) and Mother of Thyme (25) tended to use more water in Santa Fe. Moisture readings at the 6-inch depth tended to be slightly higher than at the 12-inch depth.

Some plots, at both locations early in the season, showed abnormally high moisture readings. This was due to emitters on the end of the drip lines that had started to plug up with salt. This plugging of the emitters at the end of the lines also happened at other locations. Although the emitters at the ends of these lines were replaced, it indicated that the life expectancy of the lines is probably two years if there's much salt in the water.

Approximately 57 percent of the participants used some type of drip irrigation technique, while 30 percent used sprinklers, 22 percent furrow and 19 percent flood. Some used two or more different types of irrigation systems.

Nearly 97 percent of the participants grew tomatoes. It was followed in popularity by squash (60 percent), green beans (44 percent), bell peppers (44 percent), lettuce (36 percent), cucumbers (33 percent) and chile (30 percent).