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- Author or Editor: Ronald F. Walden x
The pour-through (PT) nutrient extraction method involves collection of leachate at the container bottom that results from displacement of substrate solution by water applied to the substrate surface. The PT is a convenient and effective means of monitoring the nutritional status of the soilless container substrates used in the nursery industry, but is less convenient for large containers, particularly those used in the “pot-in-pot” system of growing trees in production containers within in-ground socket containers. We describe a simple vacuum method of extracting solution from pine bark in containers using ceramic cup samplers. When N was applied to a pine bark substrate at 56–280 mg/L, extractable N was slightly higher for the PT than for the ceramic cup method. The correlation between applied and extractable N was 0.99 for both methods. Further comparison of pine bark extract nutrient and pH levels for PT and ceramic cup methods will be presented.
Rooted cuttings of Ilex crenata Thunb. `Helleri' were grown for 12 weeks in pine bark with two root-zone temperature treatments (unheated or heated to 40C for 6 hours·day–1), two rates of limestone addition (0 or 6 kg·m–3), and three weekly N application rates (200, 400, or 600 mg·liter–1 as urea ammonium nitrate) in a factorial combination. Decreases in shoot and root dry weights due to root-zone heating (69% and 75%, respectively) or limestone addition (41% and 42%, respectively) were not influenced by N application rate. Effects of root-zone heating on medium solution characteristics, which differed in response to limestone addition, were similar for all N application levels. In unlimed pine bark at 400 mg N/liter, the pH and the NH4-N: NO3-N ratio were higher in the heated medium (5.5 and 1.15, respectively) than in the unheated medium (3.9 and 0.64, respectively) after 80 days, suggesting that 6 hours of daily exposure to 40C inhibited nitrification. The higher medium solution pH due to root-zone heating resulted in lower medium solution and shoot tissue Mn concentrations.
Pine bark-filled containers periodically fertilized with NH4-N were heated from 21C to 28, 34, 40, 46, or 52C for daily exposures of 1, 2, 4, 6, or 24 hours over 20 days. Concentrations of NH4-N and NO3-N in medium solution extracts were determined every 5 days. Medium solution NH4-N concentration was higher at constant (24 hours) exposure to 40C than at lower temperatures or exposure times. There was a similar increase in NH4-N concentration for a 2-hour·day–1 exposure to 46C, with further increases in NH4-N for longer exposure times. By day 10, NH4-N concentration was highest after 1 hour·day–1 exposure to 52C. Decreases in medium solution NO3-N concentration generally coincided with the increases in NH4-N. These results indicate that container medium thermal periods, similar to those observed in nurseries of the southern United States, may inhibit nitrification, thereby influencing NH4-N: NO3-N ratios in the medium solution of plants fertilized with predominantly ammoniacal N sources.
Container nurseries often irrigate daily with a fixed amount of water that exceeds the water-holding capacity of the container substrate, thus, leaching a portion of the applied water and nutrients. We compared the influence of daily container irrigation based on substrate moisture tension (SMT) to that of daily irrigation with a set amount on irrigation volume, container effluent volume, total effluent N content, and plant growth. Rhododendron, Ilex, and Juniperus were grown outdoors in 11.3-L containers in a pine bark-based substrate at four rates of fertilization with a controlled-release fertilizer. Drip irrigation was applied each morning until an electronic tensiometer signaled an irrigation controller that SMT was less than a set value corresponding to container capacity. Irrigation at 1.5 cm·d–1 served as the control. Irrigation treatment had little influence on growth and no influence on growth response to fertilizer rate. Irrigation volume, effluent volume, and total effluent N content were lower for each species when irrigation was based on SMT. For Juniperus, irrigation volume, effluent volume, and total effluent N content were 62%, 69%, and 60% less, respectively, for tension-based irrigation than for irrigation with a set amount.
Pine bark-filled containers periodically fertilized with a (NH4)2SO4 solution were heated from 21°C to one of 5 temperatures (28°, 34°, 40°, 46°, or 52°C) for a daily exposure duration of 1, 2, 4, 6, or 24 hours. Medium solution extracts were analyzed for NH4-N and NO3-N every 5 days for 20 days. Treatment temperature of at least 40°C and a daily exposure duration of 24 hours was necessary to inhibit nitrification, thereby increasing NH4-N concentration in the medium solution. Similar increase in NH4-N was found for a 2 hr/day exposure to 46°C, with further increases in NH4-N at longer exposure times. By day 10, the maximum level1 of NH4-N concentration in medium extracts was found after a 1 hr/day exposure to 52°C. Decreases in medium solution NO3-N concentration generally coincided with the increases in NH4-N. Results indicate that high container temperatures may increase the ratio of NH4-N to NO3-N in the medium solution of plants fertilized with predominantly ammoniacal N.
Growers report that plants on gravel bed surfaces require more frequent irrigation compared to plastic surfaces. The objective of Expt. 1 was to determine if bed surface type influenced container environment and plant growth of azalea and Japanese holly plants on plastic- or gravel-covered beds. Measurements included bed, substrate, and plant canopy temperatures; evapotranspiration (ET), stem water potential, and plant widths also were determined. The objective of Expt. 2 was to determine the amount of water retained following irrigation and drainage for four pre-irrigation substrate water contents (230%, 208%, 185%, 162%; mass basis) on gravel or plastic bed surfaces. Containers on plastic or gravel beds were irrigated, drained for 1 hour, and the amount of water retained in the container substrate was determined. In Expt. 1, plastic bed surface temperatures (0730 to 1930 hr) were higher than for gravel. Container substrate temperatures on plastic were 1°C higher than gravel from 2300 to 0400 hr with no temperature differences from 0500 to 2300 hr. There were no treatment differences for other characteristics. In Expt. 2, containers on plastic retained 21%, 15%, 23%, and 16% more water than on gravel for the 230%, 208%, 185%, 162% pre-irrigation water content treatments, respectively. When containers are seated on plastic, the bottom drainage hole is sealed resulting in more water retention compared to gravel.
Abstract
Bush-type snap beans (Phaseolus vulgaris L.) were seeded by a no-tillage method into standing wheat (Triticum aestivum L.) stubble of 8, 15, 23, 30, and 38 cm in height to evaluate the effects of stubble height on pod mechanical harvest efficiency, plant morphology, and shoot component yield. Basal internode elongation, stem plus leaf yields, pod yields, efficiency of mechanical pod harvest (MH), and height of basal pod set were related in a positive linear or curvilinear fashion to wheat stubble height. Quantity of pods missed during MH was related negatively to height of basal pod set. Harvest efficiency was maximized with 15-30-cm stubble heights, and these notillage systems yielded MH pod levels that equaled or exceeded those of a conventional tillage (plow, disk 2 times) system. Superior MH efficiency was attributed to increased basal internode length and mechanical support of the shoots by the wheat stubble.