Subirrigated Easter lilies were grown in five commercially formulated root media using one water-soluble fertilizer applied independently to each medium based on water-holding capacity and water loss. The number of irrigations ranged from 12 to 20 and the amount of applied water ranged from 5.3 to 6.8 liters for the uncovered media treatments. When the root-medium surface was covered with an evaporation barrier, the average amount of applied water was reduced by 35% compared to the uncovered media. The largest effect on root media pH was between uncovered and covered media due to the reduced amount of water applied. Similar macronutrient concentrations were measured in the five media during the experiment with few exceptions. The greatest differences in nutrient concentrations were found within the pots. The top 2.5 cm (top layer) contained nutrient concentrations up to 10 times higher than those measured in the remaining root medium (root zone) of the same pot. Covering the root-medium surface with an evaporation barrier reduced the stratification of fertilizer salts. Root-zone soluble salt concentrations of plants in the covered pots were similar to those of uncovered plants even though 36% less fertilizer was applied to the covered plants.
Yusuf Ucar, Soner Kazaz, Mehmet Atilla Askin, Köksal Aydinsakir, Abdullah Kadayifci and Ulas Senyigit
might contribute significantly to water users in decision-making. Because it is simple and easy to apply, the pan evaporation method is a commonly used method for the irrigation scheduling of plants ( Elliades, 1988 ; Wang et al., 2009 ). Studies have
Scott Henderson, David Gholami and Youbin Zheng
greenhouse microclimate conditions, such as air temperature, relative humidity, VPD, and solar radiation, can influence plant evaporation rate, water demand, and eventually irrigation frequency and amount. Microclimatic variations within a greenhouse can be
Dalong Zhang, Yuping Liu, Yang Li, Lijie Qin, Jun Li and Fei Xu
toward controlling evaporative demand according to VPD ( Lu et al., 2015 ; Zhang et al., 2015 ). Previous studies have suggested that greenhouse VPD regulation can maintain optimal ranges of temperature and relative humidity (RH) simultaneously, and
Matthew Rogoyski, Alvan Gaus, Israel Broner and Thomas Mourey
An evaporative cooling system for apple trees was implemented. The system is automated to conserve irrigation water. The automation is based on the digital, integrated thermometer and thermostat chip embedded in the artificial fruit. The thermometer–thermostat chip drives a solid state relay. The relay controls a solenoid operated valve. A typical duty cycle consisted of 1 to 2 minutes of wetting (water on) to 4 to 10 minutes drying (water off). Differences in the length of duty cycles between individual chips were observed. The reliability of the system was adequate. The waterproofing of the system's electrical components was its weak point. Irrigation water deposits accumulated on the apple fruit surface during the growing season were readily removable with a simulated brush technique.
Salvadore J. Locascio and Allen G. Smajstrla
Tomatoes (Lycopersicon esculentum Mill.) were grown on an Arredondo fine sandy soil to evaluate the effects of water quantity applied by drip irrigation scheduled by pan evaporation in a 3-year study. Water was applied to polyethylene-mulched tomatoes at 0, 0.25, 0.50, 0.75, and 1.0 times pan evaporation in one application per day. Irrigation was also scheduled with tensiometers to apply water to maintain soil water tension above 10 cb. The response to irrigation varied with rainfall during the three seasons. In an extremely dry season, fruit yields were doubled by irrigation. Total fruit yields were highest with irrigation quantities of 0.75 and 1.0 times pan and significantly lower with 0.25 and 0.50 times pan. In an extremely wet season, fruit yields were not influenced by water quantities from O to 1.0 times pan. In a third season that was wet from the middle to the end of the season, irrigation more than doubled the marketable fruit yield. However, with an increase in water quantity from 0.25 to 0.75 times pan, yield increased only from 65.9 to 74.1 t·ha-1. Water uses during the three seasons with 0.75 pan were 31.8, 31.1, and 29.6 cm, respectively. Fruit yields were similar with the 0.75-pan and 10-cb tensiometer treatments, but water uses with the latter treatment were 15.8, 17.0, and 18.4 cm during the three seasons, respectively. Tomato leaf N concentrations were reduced slightly with each increase in water quantity applied, even though N was applied with drip irrigation. Leaf N concentrations with the 10-cb treatment were generally equal to or higher than the concentrations with 0.75 pan.
Eric Simonne, Harry A. Mills and Doyle A. Smittle
Measurements of daily, 3-day, and 6-day cumulative pan evaporation using a #2 wash tub or a modified steel drum and a ruler provided an accurate, easy, and inexpensive way to schedule irrigation. Pan factors for these containers, which were covered with a 5-cm-mesh wire under humid climatic conditions, were 1.0 and 1.1, respectively.
Michael J. Perry, Preston K. Andrews and Robert G. Evans
`Fuji' apples grown in the high light intensity of arid eastern Wash. are prone to sunscald damage. Evaporative cooling with over-tree sprinklers has become a commercially acceptable method for reducing the incidence of sunscald damage. A computer-controlled, over-tree evaporative cooling system was installed in a 3-yr-old commercial `Fuji'/M.9 orchard near Walla Walla, Wash. Over-tree sprinklers (Nelson R10 Mini Rotators) applied 280 or 560 1·min-1·ha-1 (30 or 60 GPM/A) when core temperatures were ≥33C (91.4F). Fruit skin and core temperatures were monitored with thermocouples. Fruit growth was not different between treatments. Skin color was improved by cooling, but the incidence of sunscald was low in all treatments. Commercial pack-out was measured and culls were evaluated. Fruit quality was analyzed at harvest and after 14 weeks storage. Titratable acids and soluble solids were higher in the 560 1·min-1·ha-1 treatment at harvest.
W.N. Lipe, L. Baurnhardt, C.W. Wendt and D.J. Rayburn
Freeze losses to grapes in March, after mild deacclimatizing winters, is the major production risk on the Texas High Plains. Earlier studies indicated the effectiveness of evaporative cooling in reducing grape bud heat summation with a correlated delay in budbreak. Parameters relating to water-use-efficiency were identified. In the current study, these parameters were incorporated to minimize water use. Water was applied through microjets for 25 seconds every 4 minutes any time air temperature exceeded 10°C, 15°C, and Control. Bud temperatures were monitored continuously by thermocouples and data logger, and correlated with budbreak and plant development. Random bud samples were taken weekly prior to budbreak and subjected to differential thermal analysis. A freeze on March 23 (-3.5°C) resulted in differential primary bud losses to Chardonnay during budbreak, and to Cabernet Sauvignon 15 days prior to budbreak. Evaporative cooling significantly increased yields in both cultivars. Differential thermal analysis verified differences in cold stress tolerance in Chardonay prior to budbreak.
Jeff B. Million and Thomas H. Yeager
calculations. ET LF was the reference potential ET value (ETo) calculated using the 24 h of weather data collected before the input LF test date and time. ETo was calculated using a container-grown plant evaporation model ( Million et al., 2011 ), which used a