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  • Author or Editor: Wallace Pill x
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Abstract

Nitrapyrin (NI) incorporation into a peat-vermiculite medium reduced shoot growth of tomato (Lycopersicon esculentum Mill. cv. Marglobe) but this reduction was less pronounced at higher NO3-N fertilization levels. An initial 50 ppm NI application caused less growth reduction than 7, weekly 7.14 ppm applications. While increasing NO3 level had little effect on shoot ion concentration, with the exception of increasing shoot K and NO3 concentration, the increased shoot total N, Mg, and K concentrations with NI were attributed to the concentrating effect of reduced growth. Single and multiple NI applications decreased and increased, respectively, both plant water stress and medium NO3 retention. Nitrapyrin consistently increased medium NO3 concentration at the 2 highest NO3 fertilization levels. With time, however, medium NO3 concentration decreased and increased with single and multiple NI applications, respectively, relative to each other. Nitrapyrin initially decreased leaf xylem pressure potential (ψp), but with time, water stress decreased below that of the control plants with the single NI application but remained consistently high with multiple applications. Since leaf diffusive resistance and ψp were lower and transpiration rate was initially higher with the single NI application relative to the control, and since plants given the multiple NI applications had the lowest ψp and transpiration rate values throughout the study, it is hypothesized that NI reduced water uptake. That NI decreased both NO3 assimilation and uptake was evidenced by decreased shoot total N content, increased shoot NO3 content, and increased medium NO3 concentration.

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Seed treatments, gels, and planters associated with fluid drilling are reviewed in detail. The future of fluid drilling likely lies predominantly in the sowing of primed seeds rather than germinated seeds in the carrier gel. The primed seeds may be hydrated before fluid drilling to enhance germination and seedling emergence. The gel can carry a variety of chemical or biological additives appropriate for the crop and seedbed conditions. The positional advantage resulting from additive incorporation in the fluid-drilling gel represents a more eflicient, cost-effective, and environmentally sound application method than others such as binding or spraying.

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Abstract

Parsley (Petroselinum crispum L.) seeds osmoconditioned in −1.2 MPa polyethylene glycol 6000 (PEG) for 3 weeks at 15°C emerged earlier and gave higher seedling shoot fresh weights 24 days after planting than raw seeds. Further improvement in earliness of emergence was achieved by fluid-drilling the nongerminated, imbibed seeds in hydroxy ethyl cellulose gel. Germinating the osmoconditioned seeds (42% germination after 4 days at 15° in aerated water) before fluid-drilling decreased the time to 50% emergence by 52% and increased shoot fresh weight by 192% relative to raw seed performance. As emergence rate increased due to treatment, shoot fresh weight increased but emergence synchrony decreased. Neither grading seeds into density classes nor daily PEG replacement during osmoconditioning influenced seedling performance to a practical extent.

Open Access
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Seeds of `Champion' collard (Brassica oleracea L. var. acephala) were hydrated in water or a fluid-drilling gel (N-gel, hydroxyethyl cellulose) for 1 or 2 days at 20C (50 seeds/ml) before they were fluid-drilled into peat-lite in a greenhouse. Time to 50% seedling emergence from these seeds was more than 2 days earlier than from dry-sown untreated seeds, although emergence synchrony and percentage were unaffected. A second greenhouse study revealed more rapid seedling emergence from hydrated seeds that then were fluid-drilled than from dry-sown untreated seeds even when the delivery gel contained up to 25 g 9N-19.8P-12.5K/liter. Increasing fertilizer from 5 to 25 g·liter-1 led to increased shoot fresh weight 6 weeks after planting. When sown on two dates into field plots, hydrated seeds (1 day in either water or gel at 20C, 50 seeds/ml) that were fluid-drilled in 1.5% (w/v) N-gel containing 5 or 15 g 9N-19.8P-12.5K/liter yielded 42% greater final shoot fresh weights than untreated seeds sown dry.

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Kenaf (Hibiscus cannabinus L.), native to east Africa, is an annual herbaceous member of Malvaceae cultivated primarily for its bast fibers. One of many potential uses of kenaf is that of a growth medium component. Kenaf stems (xylem plus phloem) were ground and sieved to 2 to 5 mm diameter particles. The particles were combined at various volumetric percentages with other components (perlite, vermiculite, calcined clay) in 70% Sphagnum pest moss which received standard preplant fertilization. To avoid growth suppression, the kenaf must be enriched with nitrogen (soaked in NH4NO3 solution for 5 days). Impatiens and tomato bedding plant shoot growth was proportional to both the N concentration of the soak solution and the percentage of N-soaked kenaf in the medium. The N soak solution should be £ 2000 mg N/liter with 30% kenaf or £ 4000 mg N/liter with 10% kenaf. Physical properties (bulk density, total porosity, air porosity and container capacity) of kenaf media were similar to those of a commercial peat-lite. The optimal medium for bedding plant production was 70% pest + 15% calcined clay + 15% kenaf soaked in 2000 mg N/liter. The N-soaked kenaf served successfully both as a medium bulking component and as a slow-release N supply.

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Seeds of purple coneflower (Echinacea purpurea (L.) Moench were osmotically primed (OSP) in polyethylene glycol (PEG) or matrically primed in expanded vermiculite No. 5 (solid matrix priming, SMP). With both OSP or SHP at 15C, 10-day exposure to -0.4 MPa resulted in lowered time to 50% germination (T,) and higher germination percentage than shorter exposure (5-day) or lower water potential (-1.5 MPa). SMP- and OSP-seeds performed similarly in a greenhouse trial, resulting in 80% and 34% seedling emergence at 23C and 37C, respectively, compared to 58% and 27% for non-primed seeds. Seedling emergence rate and synchrony from primed seeds were greater than from non-primed seeds at both temperatures. An incubator study established that adding 10-4M GA3 and 10 mN ethephon (2-chloroethylphosphonic acid) to the PEG or vermiculite resulted in lower T50 and higher germination percentage than priming without these growth regulators. A further incubator study established that less-expensive trade products (Pro-Gibb Pius 2X) and Florel could substitute for the reagent-grade growth regulators. Seeds primed in PEG or vermiculite containing 10-4M GA3 from Pro-Gibb Plus 2X and 10 mM ethephon from Floral had lower T50 and higher percentage emergence in a greenhouse trial than seeds primed without growth regulators. Compared to the non-primed seeds, these treated seeds had 29% greater seedling emergence and 61% less time to 50% emergence.

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Achievement of head size uniformity at final harvest reduces loss and increases profitability for the hydroponic lettuce grower. Shoot fresh weight of `Cortina' lettuce (Lactuca sativa L.) at 7 or 21 days after planting (DAP) was inversely proportional to the number of days required for seedling emergence, and was greater for raw than for pelleted seeds. Head fresh weight at final harvest (61 DAP) was directly proportional to seedling length at 21 DAP, but raw and pelleted seeds produced equal head weights. Thus, initial seed (seedling) vigor differences were maintained to final harvest. Osmotic seed priming (–1.5 MPa KH2PO4, 20 h, dark) led to increased germination rate at 15, 25, and 35C; had no effect on germination synchrony; and increased germination percentage only at 35C. Covering raw or pelleted seeds sown in depressions of the phenolic foam trays with fine (No. 5) vermiculite compared to leaving the seeds uncovered, and soaking the trays in hydroponic solution rather than water, increased seedling shoot fresh weights. Seeds sown on their first day of germination or primed seeds gave greater seedling shoot fresh weights than pelleted seeds. However, the more uniform seedling shoot fresh weights from germinated seeds than from primed seeds was associated with more rapid and synchronous seedling emergence.

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Kenaf core (xylem) particles (2 to 4 mm in diameter) were submersed in ammonium nitrate solutions (0 to 5000 mg N/liter) for 5 days. The kenaf was incorporated into complementary components as 30% kenaf: 70%. sphagnum moss or 10% kenaf: 10% vermiculite: 10% calcined clay: 70% sphagnum moss. These media received standard preplant fertilizer additions. Tomato and impatiens bedding plant shoot dry weights increased with up to 5000 mg N/liter in media containing 10% kenaf and with up to 3000 mg N/liter in media containing 30% kenaf. By selecting the N concentration of the kenaf soak solution, shoot growth could be matched to that achieved with commercial peat-lites after any post-transplanting period (2 to 9 weeks). A further study revealed that kenaf was an effective carrier for Bonzi and Sumagic growth regulators. By combining N-soaked kenaf with growth-regulator-soaked kenaf in the growth medium, bedding plant shoot growth was healthy but restricted.

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Kenaf stems were ground and sieved to yield fine (<2mm), medium (2 to 6 mm) or coarse (6 to 12 mm) grades. These grades were mixed at 25, 50 or 75% volumes in sphagnum peatmoss and then provided standard basal fertilization. Tomato and impatiens shoot fresh weights 4 weeks after transplanting (50 mg N.liter-1 daily liquid feed) were greatest in 25% medium kenaf, being 68 and 89%, respectively, those in peat-lite (ProMix BX). In a further study, medium kenaf was soaked for 3 days in 5000, 10000 or 15000 mg N.liter-1 from 20N-4. 3P-8.6K then mixed at 25% volume in peatmoss. Tomato seedlings transplanted into these media were provided 0, 100, 300 or 500 mg N.liter-1 daily liquid feed (LF) from 20N-4.3P-8.6K. With ≥100 mg N.liter-1 LF, soak solution concentration had no effect on shoot fresh weight. With 0 mg N.liter-1 LF however, kenaf media soaked in 10000 or 15000 mg N.liter-1 yielded greater shoot fresh weights than ProMix with 100 mg N.liter-1, LF.

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The utility of Ironrich (IR), a tertiary mineral co-product from TiO2 production, as a growth medium component was investigated. All complementary bulking components (10 to 50% volume) gave reduced shoot fresh weights of tomato, impatiens or perennial ryegrass relative to Fairgrow (FG, co-composted solid waste and sewage sludge). Shoot fresh weights of impatiens and tomato grown in 50% IR with FG were similar to those grown in commercial peat-lites. When provided 200 mg N litre-1 daily, chard shoot fresh weights, beet root fresh weights, and tomato fruit fresh weights from plants grown in 50% IR plus 50% FG were not significantly different from those grown in 50% silt loam plus 50% FG. Tissue Cd, Cr, Ni, and Pb concentrations from plants grown in 50% combinations of FG with IR or silt loam were below the limits of detection. IR plus FG with N-P-K fertilization provided a satisfactory greenhouse growth medium. We project that IR + FG will constitute a satisfactory synthetic topsoil.

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