Rooted cuttings of `Gutbier V-l 4 Glory poinsettia (Euphorbia pulcherrima Willd. ex Klotzsch) were grown in 15-cm pots using two irrigation methods, two water-soluble fertilization schedules, and two preplant root-media fertilization rates. No difference in shoot growth occurred with either top watering with 33% leaching or subirrigation. 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 with both irrigation methods. Constant applications of28 mol N/m3 water-soluble fertilizer (WSF) limited shoot and root growth as measured at 3 and 8 weeks compared to a weekly increase in the concentration of WSF from 0 to 28 mol N/m3 in 7 mol N/m3 increments over a S-week period. The additional incorporation of 0.27 kg·m-3 mineral N to Metro Mix 510 before planting had no effect on fresh- or dry-weight accumulation. When the root-medium surface was covered by an evaporation barrier, 46% less water and 41% less N fertilizer were applied to plants of similar size, and higher root-zone nutrient levels were maintained over the 8 weeks of the experiment. The evaporation barrier had the greatest effect on increasing root-zone nutrient concentrations and reducing the growth of subirrigated plants.
William R. Argo
Acceptable physical properties are an integral part of root-media quality. However, there is no one growing medium that works best in all situations because root-media physical properties are not constant, but rather can be affected by the grower. Understanding the root environment under production conditions requires an understanding of the dynamic nature of air : water : solid ratio in the medium. The objective of this review is to consider key aspects of root-medium physical properties, which include bulk density and particle size, container capacity, media settling, water absorption, rewettability, moisture release characteristics, and water loss due to evaporation from the root-medium surface.
J. Ryan Stewart and Roger Kjelgren
Infrared sensors were used to quantify canopy temperature and thus detect differences in incipient water stress between a cool-season grass [Kentucky bluegrass (KBG) (Poa pratensis)] and a warm-season grass [buffalograss (BG) (Buchloe dactyloides)]. The infrared sensors, connected to a datalogger, measured average hourly leaf–air temperatures (TL–TA) 1 m above eight replicate plots of Kentucky bluegrass and eight replicate plots of buffalograss. Air temperature and relative humidity from a nearby weather station were used to calculate the average hourly vapor pressure deficit (VPD). In late July, we ceased irrigating and measured TL–TA and soil water content while allowing the turf to dry down for 5 weeks. Soil water content was measured with a neutron probe. Both species exhibited a significant relationship between TL–TA and VPD. As the VPD increased, TL–TA decreased in both species (KBG r 2 = 0.73, BG r 2 = 0.71) on the 2nd day after an irrigation during well-watered conditions. An artifact was created on the first day after an irrigation as a result of excessive surface evaporation. KBG and BG were similar under well-watered conditions. KBG had a higher TL–TA after 4 to 5 days without irrigation. By contrast, BG did not have a higher TL–TA until 25 to 30 days without irrigation. Part of BG's drought avoidance was extraction of soil water down to 0.9 m vs. 0.45 m for KBG.
Robert Wiedenfeld and Robert Stubblefield
Plastic mulch ground cover and drip irrigation have produced substantial increases in yield and earliness of melons. However, such practices affect water movement, and nutrient and salt distribution in the soil. Salt levels in the soil after a melon crop using drip or flood irrigation increased in bare soil but decreased where plastic mulch had been used. Apparently capillary rise of water in response to surface evaporation brought salts up into the root zone. Very little of the applied N was detectable at the end of the study. However, enhanced early vine growth due to N application where drip irrigated but not where flood irrigated indicated that flood irrigation may have caused earlier N losses. Yield responses to N regardless of irrigation method indicated that early availability may have been most important. Yield increases were found for drip vs flood irrigation, and for plastic mulch vs bare soil, both of which may have been earliness effects; but the later treatments did not get the chance to catch up due to the occurrence of vine decline.
Mark V. Yelanich and John A. Biernbaum
The evaporation of water is a major source of water loss from potted plants which can be eliminated by placing a barrier at the exposed surface of media in the pot. To better understand the effect of reducing surface evaporation on growth and media nutrient concentration, 15 cm subirrigated poinsettias were produced with and without a pot cover. Both treatments received the same quantity of fertilizer, 75 mg·week-1 N for a total of 13 fertilizations. Uncovered pots received 12 more irrigations than pots with covers (20 vs. 32). Sixteen weeks after planting, covered plants had significantly less leaf area (2175 vs 2628 cm2), bract area (1655 vs 2137 cm2), height (24.1 vs 27.6 cm), fresh mass (116 vs 144 g) and dry mass (17 vs 20 g) than uncovered plants. Concentrations of N, P, K, Ca and Mg and EC (4.23 vs 2.65 mS·cm-1) were higher in the root-zone of covered plants than in uncovered plant. Covering the media surface did reduce the EC and the concentrations of N, P, K, Ca and Mg in the top layer (eg 13.47 mS·cm-1 vs 15.74 mS·cm-1) but stratification of salts to the top layer still occurred. Fertilizer salts in the top layer were shown to be less available to the plant than those in the root zone.
Isabelle Lemay, Jean Caron, Martine Dorais, and Steeve Pepin
sawdust peat-based substrates, irrigation strategies (dripper distribution and number, absence of surface evaporation, volume of leaching) played a key role in the salt build-up process and in subsequent leaching. Substrate irrigation management. Because
Richard C. Beeson Jr
environment characterized by ETo, whereas substrate evaporation was not or was only weakly coupled as evidenced by consistent surface evaporation rates ( Fig. 1 ). For young plants, PCA was quite small, 6% to 12% of the top substrate surface area (data not
Jeffery C. Kallestad, John G. Mexal, Theodore W. Sammis, and Richard Heerema
months. However, days with rainfall tend to be cooler, resulting in lower ET, which in itself may compensate for the effect of leaf interception and surface evaporation. The assumption built into the water balance model is that all of the station
Alex B. Daniels, David M. Barnard, Phillip L. Chapman, and William L. Bauerle
effective irrigation is required to replace water lost through transpiration and surface evaporation. Quantifying the amount of water to be replaced requires accurate characterization of the availability of water within the container and the rate of plant
Raquel Valdés, Julián Miralles, Jesús Ochoa, Sebastián Bañón, and María Jesús Sánchez-Blanco
water lost from a potted plant was caused by evaporation from the substrate surface. Evaporation from the substrate surface leads to the accumulation of salts at the top of the pot ( Guttormsen, 1969 ). In our experiment we used coconut fiber as a