Search Results

You are looking at 1 - 10 of 181 items for :

  • Journal of the American Society for Horticultural Science x
Clear All

The use of potential evapotranspiration (PET) estimates to identify irrigation timing for greenhouse tomatoes (Lycopersicon esculentum Mill.) grown in peat-based substrate was evaluated for a spring and fall crop. PET (using the Penman equation) was calculated from leaf, wet and dry bulb temperatures, and incident and reflected photosynthetic photon flux. Substrate matric potential (SMP) was monitored continuously using electronic tensiometers. Two irrigation starting setpoints (-4.5 and -6.5 kPa SMP) and two nutrient solution electrical conductivity (EC) treatments (1.5 and 3.0 dS·m-1) were factorially combined in a completely randomized design. Irrigation frequency was greater in treatments irrigated at -4.5 than at -6.5 kPa. The integral of calculated PET values was correlated with SMP for both experiments. Accumulated PET values were higher at the start of irrigation in the -6.5-kPa treatments for spring and fall crops. Nutrient solution EC did not influence irrigation frequency. Leaf pressure potential (LPP) was correlated to PET-predicted LPP (r 2 > 0.56) in plants subjected to high EC, low (-6.5 kPa) matric potential setpoint, or both treatments. PET and electronic tensiometer technology can be used jointly to improve irrigation management for tomatoes grown in peat-based substrates by more accurately responding to crop needs for water and nutrients.

Free access

Abstract

The relationship between water extraction (1:1.5) values and nutrient uptake in geranium (Pelargonium × hortorum Bailey) growing in moss peat (peat), bark, or moss peat and soil media was investigated. Nitrogen, P, and K fertilizers were incorporated in increments in the starting media and applied again in solution, about at the crop midpoint. Desirable nutrient N(NH4 +-N + NO3 --N), P(H2PO4 --P) and K(K+) values (DV) from media analysis at the start of the experiments (MDV) and midway to flowering (FDV) also were calculated from regression equations on the basis of maximum growth rates, maximum dry weight production at midharvest, and final harvest. The relationships between plant uptake of N, P, and K and the water extract concentrations were generally very good, except for K in bark for both harvests and in peat at the first harvest, and an underestimated P uptake in peat + soil and in bark. The media DV obtained using growth data were broadly similar to those using plant dry weight data, although somewhat lower for N during the early growing period.

Open Access

Abbreviations: AW, available water; BD, bulk density; GW, gravitational water; PBS, peat-based substrate; % REC, intensity of root-length endomycorrhizae colonization; VAM, vesicular-arbuscular mycorrhizal; WCS, water content at saturation. 1

Free access

Abstract

Spagnum peat, perlite, vermiculite, and six media formulated (by volume) from these constituents (2:1, 1:1, 1:2 peat: perlite; 2:1, 1:1, 1:2 peat: vermiculite) were limed with 0, 0.9, 1.8, 2.7. 3.6, 5.4, 7.2, and 9.0 kg∙m−3 dolomite [CaMg(CO3)2]. Media were wet to container capacity with distilled/deionized (d/d) water, incubated at 25° ±3°C, and pH determined at day 0, 2, 5, 7, 14, 28, 56, and 84. Liming reactions in mixes could not be predicted from reactions occurring in sphagnum peat, perlite, and vermiculite constituents alone. Although sphagnum peat made the major contribution to liming reactions, both perlite and vermiculite were found to contribute to liming responses of media in which they were incorporated. The major portion of pH change due to incorporation of pulverized dolomite in peat-based media occurred within 2 days. Change in pH was complete within 14 days.

Open Access

Lining of shipping cases with low-density polyethylene (PE) greatly reduced moisture loss from packing media and bulbs of Lilium longjlorum Thunb. `Nellie White' during shipping, handling, and case vernalization (CV). Three years of studies showed that use of PE liners accelerated floral sprout emergence above the growing medium, floral bud initiation, and flowering date. Effects of case lining became more pronounced as the initial water content of the spagnum peat packing was lowered. Case lining sometimes increased apical meristem diameters measured immediately after vernalization, or 2 or 4 weeks after bulb planting, but flower bud number was never significantly increased. Root growth during the first 4 weeks after planting was not affected by case lining. Bulb scale and basal plate water contents at planting were greater in lined than nonlined cases and when packed in peat of relatively high moisture content. Handling and vernalization of bulbs in PE-lined cases without a packing medium resulted in similar bulb forcing characteristics as in bulbs held in PE-lined cases packed with sphagnum peat.

Free access

Abstract

Peat-sand (1:1, by volume) and wood-sand (2:1, by volume) mixes in 10 cm plastic pots were planted with Epipremnum aureum Linden & Andre cv. Tricolor (pothos), Coleus glumei Benth (coleus), and Brassaia actinophylla Endl. (schefflera). After the pH of the leachate had dropped to between 4.0 and 5.0, pots received a single irrigation with solutions NaHCO3 and KHCO3. For the peat mix, the highest concentrations (0.20 M) of NaHCO3 and KHCO3 raised the leachate pH to nearly 9.0; the pH subsequently dropped most rapidly in pots containing coleus and schefflera, and slowest with pothos. In pots containing the wood-sand mix, the pH climbed as high as 8.0 immediately after treatment with 0.08 m KHCO3, then decreased slowly in pothos and more rapidly with the other 2 species. In peat mixes, the final leachate pH was nearly one unit greater than the saturation paste pH of the soil. In wood-sand pots, mix from the bottom half of the pot was always lower in pH than mix from the top half. Except for schefflera the pH of the last leachate obtained was nearer the pH of the bottom half of the pot than that of the top half.

Open Access
Author:

Abstract

Chrysanthemum plants (Chrysanthemum morifolium Ramat. cv. Bright Golden Anne) were grown for 84 days in plastic pots containing media treated with inorganic fertilizers or liquid sewage sludge, added at a rate of 50, 100, or 200 ml/week, to determine if sludge could be used as a fertilizer. Plants grown with sludge at all application rates had higher N and lower K concentrations compared to plants grown with inorganic fertilizers. Leaf concentration of P, Ca, Mg, Fe, Zn, Cu, Cd, Ni, and Pb of plants grown with 50 ml sludge/week were similar to plants receiving inorganic fertilizers. As sludge application rate increased, leaf concentrations of Fe and Cu increased of plants grown in media consisting of all sand or all peat and Zn increased in leaves of plants grown in the standard greenhouse media (1 soil: 1 sand:l peat, by volume). Sludge-treated media had a higher pH and extractable Cu concentration, and a lower extractable K concentration, than media without sludge. Plants receiving 50 ml sludge/week grew as well as plants grown with inorganic fertilizers.

Open Access

Heavy metal-sensitive `Express Orchid' petunias (Petunia ×hybrida Hort Vilm.-Andr. `Express Orchid') were grown in substrates of 2 green yard waste compost: 3 peat (v/v) with target Cu contents of 100 and 200 mg·kg-1 at varying pH. Iron supply was also varied. Copper contents of the substrate were determined by H2O, NH4NO3, NH4OAc, CaCl2, CaCl2-DTPA, and aqua regia extraction. Plant Cu concentration increased with increasing Cu supply and decreasing pH, indicating that Cu phytoavailability depended on substrate pH. Extraction of fresh substrates with CaCl2-DTPA provided a good prediction of plant Cu concentration and reflected well the influence of pH on Cu phytoavailability. The percentage of CaCl2-DTPA extractable Cu increased with decreasing pH. Extractions of Cu with NH4NO3, H2O, NH4OAc, and CaCl2 resulted in very low extractable amounts and hence were not suitable. Plants showed Cu toxicity induced iron-like deficiency chlorosis, which was alleviated by additional Fe supply. This Fe supply did not seem to affect total Fe concentration of petunias, but reduced Cu concentration of the shoots. Since yield reduction was not observed, the occurrence of chlorosis during the culture period was chosen as the toxicity parameter, resulting in a Cu threshold toxicity level of 12.3 mg.kg-1 plant dry weight. From this, a threshold toxicity level for CaCl2-DTPA extractable Cu in compost-peat substrates of 3 mg.L-1 substrate was determined. Chemical name used: diethylenetriamine-pentaacetic acid (DTPA).

Free access

Water retention at effective water-holding capacity (EWHC) and container capacity (CCAP) were measured in four rockwool-peat potting media amended with a wetting agent and/or a hydrophilic gel in pots 12 cm tall containing 445 cm3 medium, and irrigated by capillary mat, flood-and-drain, trickle emitter, or overhead sprinkler. Water retention was measured by weighing. Irrigation was continued until EWHC (i.e., net water retention when no weight increase could be obtained by further irrigation) was reached. CCAP (i.e., net water retention following saturation and free drainage) was measured at the end of each experiment. Irrigation method and medium amendments significantly affected EWHC. Rank order of irrigation treatments was sprinkler ≥ trickle > flood and drain ≥ mat. Hydrophilic gel increased both EWHC and CCAP, while the wetting agent increased EWHC but decreased or had no effect on CCAP. Significant interactions of gel and wetting agent were observed in some media. EWHC was less than CCAP, and EWHC was better correlated with CCAP with trickle emitter and overhead sprinkler irrigation than with capillary mat and flood-and-drain irrigation.

Free access
Authors: , , and

Abstract

The effects of peat: vermiculite mixes on increased growth response of radish (Raphanus sativus L. ‘Early Scarlet Globe’) induced by Trichoderma harzianum Rifai (isolate T-12) were investigated. Canadian sphagnum peat and vermiculite were mixed in various ratios to form 0-100% peat mixes. Four levels of T-12 amendment were added to these mixes—0%, 2%, 5%, and 10% (v/v) or 0%, 0.1%, 1%, and 10%. In general, increasing levels of T-12 amendment induced linear increases in radish dry weights after 4 and 5 weeks. Greatest increases were seen in mixes containing 20% peat or 80% peat. The smallest increases were observed when T. harzianum was added to 0% peat or 100% peat mixes. There was no effect on the population densities of T-12 after it was introduced into the mixes. No Pythium spp. or root disease were detected in the mixes, suggesting that T. harzianum, a biological control agent, can increase plant growth independent of any detectable root pathogens.

Open Access