A small inexpensive (less than $1000) container yard, measuring 10 × 10 ft square, with an automatic irrigation system was designed for schools participating in the Louisiana State University Coastal Roots Program: A School Seedling Nursery Program for Habitat Restoration. Students helped install the container yard on their school site and oversee native plant production through the course of the school year. Teachers and other school staff checked the nursery during summer months to ensure that the irrigation system was working properly and the plants were healthy. Students grew ≈1000 restoration seedlings per year in their container yard. Each year they transplanted their seedlings and grass plugs on trips to habitat restoration sites across Louisiana's coastal zone. Since the inception of the program in 2000, the students using this container yard design have produced nearly 24,500 trees and shrubs and over 8000 grass plugs.
Edward W. Bush and Pamela B. Blanchard
Nastaran Basiri Jahromi, Amy Fulcher, Forbes Walker, James Altland, Wesley Wright, and Neal Eash
Controlling irrigation using timers or manually operated systems is the most common irrigation scheduling method in outdoor container production systems. Improving irrigation efficiency can be achieved by scheduling irrigation based on plant water needs and the appropriate use of sensors rather than relying on periodically adjusting irrigation volume based on perceived water needs. Substrate amendments such as biochar, a carbon (C)-rich by-product of pyrolysis or gasification, can increase the amount of available water and improve irrigation efficiency and plant growth. Previous work examined two on-demand irrigation schedules in controlled indoor (greenhouse) environments. The goal of this study was to evaluate the impact of these on-demand irrigation schedules and hardwood biochar on water use and biomass gain of container-grown Hydrangea paniculata ‘Silver Dollar’ in a typical outdoor nursery production environment. Eighteen independently controlled irrigation zones were designed to test three irrigation schedules on ‘Silver Dollar’ hydrangea grown in pine bark amended with 0% or 25% hardwood biochar. The three irrigation schedules were conventional irrigation and two on-demand schedules, which were based on substrate physical properties or plant physiology. Conventional irrigation delivered 1.8 cm water in one event each day. The scheduling of substrate-based irrigation was based on the soilless substrate moisture characteristic curve, applying water whenever the substrate water content corresponding to a substrate water potential of –10 kPa was reached. The plant-based irrigation schedule was based on a specific substrate moisture content derived from a previously defined relationship between substrate moisture content and photosynthetic rate, maintaining the volumetric water content (VWC) to support photosynthesis at 90% of the maximum predicted photosynthetic rate. Total water use for the substrate-based irrigation was the same as for the conventional system; the plant-based system used significantly less water. However, plant dry weight was 22% and 15% greater, water use efficiency (WUE) was 40% and 40% greater, and total leachate volume was 25% and 30% less for the substrate-based and plant-based irrigation scheduling systems, respectively, than for conventional irrigation. The 25% biochar amendment rate reduced leachate volume per irrigation event, and leaching fraction, but did not affect total water use or plant dry weight. This research demonstrated that on-demand irrigation scheduling that is plant based or substrate based could be an effective approach to increase WUE for container-grown nursery crops without affecting plant growth negatively.
Albert E. Smith and Will Corley
Lysimeters were developed in the greenhouse for simulating golf course greens with `Tifdwarf' bermudagrass and `Penncross' bentgrass overlying USGA specified rooting substratum. The lysimeters were constructed by subtending wooden flats containing turfgrass (38 × 38 × 14 cm deep) with polyvinyl chloride tubes (15 cm diam. × 52 cm deep) containing USGA-recommended rooting mixture for each turfgrass. The base of the tubes was capped with a closure containing an exit port for collecting the effluent drainage. An automatic irrigation system was developed by mounting flat fan nozzles on a cable driven roller 55 cm above the grass sod. The automatic water system is calibrated to irrigate at a rate of 0.1 cm min-1 for predetermined time-periods and volumes. The water flow through the lysimeters is uniform with a coefficient of variation less than 10% for 36 lysimeters. Data on chemical movement following treatment with three herbicides and weekly applications of fertilizer will be presented.
Sudeep Vyapari*, S.M. Scheiber, and Richard C. Beeson Jr.
During Fall 2003, a study was conducted to determine the effect of soil amendments on growth and response of Pentas lanceolata `New Look Red' in the landscape. Pentas were grown in 250L drainage lysimeters in an open-sided clear polyethylene covered shelter filled with local top soil (Apopka fine sand). The treatments used were non-amended top soil (control) and soil amended with either compost (5% by volume) or clay (5% by volume) in the top 15 cm. Best Management Practices were followed. Irrigation frequency and rate were regulated using a tensiometer-controlled automatic irrigation system. When plant available water in each soil type had declined to 70% or less, the plants were irrigated back to field capacity. Data were recorded on initial and final growth indices, shoot dry weight, and root dry weight. Final growth indices between control and soil amended with compost were not different; however, growth in the clay-based soil was significantly less than the compost-based soil type. The mean shoot dry weight (77.2 g) produced from plants in compost amended soil type was significantly higher than either control (57.45 g) or clay amended (54.92 g) soil types. No significant differences were found for either initial growth indices or root dry weight among the three treatments.
S.M. Scheiber and Richard C. Beeson Jr.
Petunia ×hybrida Vilm. `Midnight' plants were grown in drainage lysimeters to evaluate growth in response to alternative irrigation strategies. Irrigation treatments were tensiometer-regulated automatic irrigation systems, regularly scheduled irrigation using an automated controller, and human perception of plant irrigation need (manual watering). Mean irrigation volumes were reduced by manual watering and tensiometer-regulated treatments, compared to the automated controller. Total mean irrigation volume applied by the automated controller (460 L) was significantly greater than received by the manually watered (293 L) or tensiometer-regulated (286 L) treatments. Regularly scheduled irrigation using an automated controller resulted in higher assimilation rates, final shoot dry mass, final biomass, shoot to root ratios, and growth indices compared to other irrigation methods tested. Assimilation rates were significantly higher for tensiometer-controlled irrigation than the manually watered treatment, but no differences were reported between these two treatments for growth parameters. Visual observations indicated aesthetic quality was compromised among tensiometer-regulated and manually watered treatments relative to the automated controller treatment.
Jack W. Buxton and Wenwei Jia
Cabbage seed was germinated and grown to transplanting size in a 98-cell tray using an automatic irrigation system based on the principle of maintaining a constant water table (CWT) relative to the growing medium in transplant trays. Seedlings obtained a nutrient solution from a capillary mat with one end suspended in a trough containing the solution. The distance between the nutrient solution surface and the transplant tray bottom was regulated with a water level controller. The nutrient solution was resupplied from a larger reservoir. A polyester material on top of the capillary mat allowed solution movement to the roots but prevented root penetration into the mat. The water table placement below the tray determined the water content in the growing medium. Seedling growth was evaluated using two growing media combined with two water table placements. Excellent quality seedlings were produced; the CWT irrigation system satisfactory provided water and nutrients for the duration of the crop. The only problems observed were dry cells, less than 2%, because of no media–mat contact and algae growth on the media surface using the higher water table. The CWT irrigation system is adaptable to existing greenhouse vegetable transplant production systems. It is automatic and can provide a constant optimum amount of moisture for seedling growing. It can be adjusted for phases of seedling growing such as more water during germination and can create water stress near transplanting time to either harden off or hold plants because of unfavorable planting conditions.
Sloane M. Scheiber* and Richard C. Beeson Jr.
Petunia `Midnight' were grown in drainage lysimeters in an open-sided clear polyethylene covered shelter to evaluate growth responses in response to alternative irrigation strategies. Three irrigation methods were evaluated: tensiometer-controlled automatic irrigation system, regularly scheduled irrigation utilizing an automated controller, and human perception of plant irrigation need. Drainage lysimeters (250 L) were backfilled with native sand field soil to simulate landscape conditions and managed with Best Management Practices. Following establishment, lysimeters irrigated by an automated controller were irrigated 1.3 cm daily. Tensiometer-controlled lysimeters were irrigated when plant available water (2.5 kPa to 1.5 MPa) had declined to 70% or less, and were irrigated back to field capacity. Canopy growth indices and leaf gas exchange measurements were evaluated relative to irrigation strategies. Actual evapotranspiration was calculated for each replication. Daily irrigation resulted in significantly higher assimilation rates, transpiration rates, and final shoot dry weights than the other treatments tested. Assimilation rates and transpiration rates were significantly higher for tensiometer-controlled irrigation than the human judged treatment, but no differences were found in final shoot dry mass.
J. Norrie, M.E.D. Graham, P.A. Dubé, and A. Gosselin
An automatic irrigation system was designed for use on green-house tomatoes growing in peat-based substrates. This system uses electronic tensiometers to monitor continuously substrate matric potential (SMP) in peat-bags. The system also uses the Penman equation to evaluate potential evapotranspiration (PET) through the acquisition of many greenhouse environmental parameters. Through a series of linear equations, estimates of PET are used in a computer-controller system to vary the electrical conductivity (EC) of irrigated nutrient solutions, as well as SMP setpoints at which irrigations are started. Such modifications to current irrigation management systems may improve fruit quality and reduce the risk of water stress during periods of high PET by irrigating more frequently with less-concentrated nutrient solutions. Conversely, during periods of low PET, irrigation is less frequent with more-concentrated nutrient solutions. Although no differences were found in fruit number or overall yield using variable nutrient solution EC, plant fresh weight was higher in those treatments. It is concluded that an integrated tensiometer-PET system may give increased precision to irrigation management and the control of crop growth in the greenhouse.
Young Soon Kwon, Soon-Il Kwon, Jeong-Hee Kim, Moo Yong Park, Jong Taek Park, and Jinwook Lee
irrigation system equipped with a tensiometer (Irrometer SR; Irrometer Company Inc., Riverside, CA). Data from the nearest meteorological station showed that the daily mean, maximum, and minimum air temperatures of the experimental area in the last decade
Qiang Liu, Youping Sun, James Altland, and Genhua Niu
–controlled automatic irrigation system. Substrate volumetric water content (VWC, %) is volume of water/volume of substrate. Plant height, leaf area, and shoot DW of tatarian dogwood seedlings decreased linearly with decreasing VWC with the linear regression