 The goal of this study is to determine the ir-rigation requirements of the most common-ly used bedding plant annuals in Colorado, under Colorado conditions. We will be de-termining crop coeffients for these bedding plants with Evapotranspiration (ET) data. Evapotranspiration is the amount of water required by a plant. In calculation ET, factors such as solar effect, temperature, humidity and wind are all factored. ET is expressed in inches of water required, then usually converted into a weekly value. The standard in horticulture is Kentucky Blue Grass, Poa pratensis at an ET of 1 or 100%. The maximum weekly ET in most areas of Colorado is 2 inches/week.
All plants were drip irrigated with drip tape. Plants were pulse irrigated, up to 3 application in the same evening. Plants were planted May 28th on 10 inch centers. Soil was ammended with 2 yards of peat moss per 1000 sq. ft. A full season complete nutrient, slow release fertilzer was used at planting (Hardy Starts 7-2-6 at 25lb/1000sq. ft.). Bark mulch was used to reduce surface evaporation and minimize weed pressure. All plants were allowed a two week period of watering at 100% of ET to become established prior to the irrigation treatments beginning. Irrigation of the plants was done using an ET Controller, which is a comput-erized watering clock with the ability to have cellular down loads of the changing ET value. The clocks are updated daily by the controllers' manufacturer Hydropoint, (based out of California) which uses weath-er station data to update these ET values. Typically irrigation schedules change with varying weekly ET values: When irri-gated the treatments usually ran about 20-30 minutes 3 times during an evening with at least a 30 minute soak time in between each cycle. The 100% plots were irrigated roughly every other day, 75% every 3 or 4 days, 50% every 5 to 6 days, 25% every 8 to 10 days, and 0% was irrigated for only 2 weeks to get established. Based on the Garden Center of Colo-rado X-rated program, the ratings are as fol-lows: An X-rating is up to one inch of water per square foot per week; a XX-rating is one half an inch of water per week; and XXX-rating is a half an inch of water every other week. Results of the study were based on percent coverage, dry weight and photo-graphic data. Plants that performed well down to 0% ET or XXX-rated (only natural rain fall after 2 week establishment) include: Pe-tunia hybrida 'Merlin White' and Verbena x speciosa 'Imagination Blue'. Plants that performed well down to 25% ET or XX-rated, include; Rudbeckia hir-ta 'Indian Summer', Tagetes erecta (African Marigold) 'Inca Yellow', and Zinnia elegans 'Dreamland Red'. Plants than performed well down to 50% ET or X-rated include: Antirrhinum ma-jus (Snapdragons) 'Sonnet Yellow', Cathar-anthus roseus (Vinca) 'Peppermint Cooler', Dianthus hybrida 'First Love', Lobelia erinus 'Cobalt Blue', Lobularia maritima (Sweet Alyssum) 'Carpet White', Pelargonium horto-rum (Zonal Geranium) 'Kim Red', Portulaca grandiflora (Moss Rose) 'Sundial Mix', Salvia farinacea 'Rhea Blue', Senecio cineraria (Dusty Miller) 'Silver Dust', Tagestes patula (French Marigold) 'Bonanza Yellow', and Zin-nia angustifolia 'Crystal White'. Plants that performed well down to 75% ET include: Viola x wittrockiana (Pan-sy) 'Crown Gold'. Plants that performed well at 100% ET include: Begonia x semperflorens 'Vodka' and Impatiens walleriana 'Tempo White'. All photos were taken August 13, 2003. |
The top 19 selling bedding plants and turf were irrigated under 5 different regimes. The irrigation treatments were based on the ET value: 100% of ET, 75% of ET, 50% of ET, 25% of ET, and 0% ET.
To view the Efficiency Study imgages click on pages 2 through 6
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About X-Ratings and drought tolerant plants
