Substrate Nutrient Concentration Research Articles

Growth and Quality Response of Four Container-grown Nursery Crop Species to Low-phosphorus Controlled-release Fertilizer

The amount of phosphorus (P) conventionally recommended and applied to container nursery crops commonly exceeds plant requirements, resulting in unused P leaching from containers and potentially contributing to surface water impairment. An experiment was replicated in the Middle Atlantic Coastal Plain (MACP) and Ridge and Valley ecoregions of Virginia to compare the effect of a low-P controlled-release fertilizer (CRF, 0.9% or 1.4% P depending on species) vs. a conventional CRF formulation (control, 1.7% P) on plant shoot growth, crop quality, and substrate nutrient concentrations of four species: ‘Natchez’ crape myrtle (Lagerstroemia indica × Lagerstroemia fauriei), ‘Roblec’ Encore azalea (Rhododendron hybrid), ‘Radrazz’ Knock Out rose (Rosa hybrid), and ‘Green Giant’ arborvitae (Thuja plicata × Thuja standishii). In both ecoregions, the low-P CRF resulted in 9% to 26% lower shoot dry weight in all four species compared with those given the conventional formulation, but quality ratings for two economically important species, ‘Radrazz’ Knock Out rose and ‘Green Giant’ arborvitae, were similar between treatments. When fertilized with the low-P CRF, ‘Roblec’ Encore azalea and ‘Natchez’ crape myrtle in both ecoregions, and ‘Green Giant’ arborvitae in the MACP ecoregion had ∼56% to 75% lower substrate pore-water P concentrations than those that received the control CRF. Nitrate-nitrogen (N) concentrations in substrate pore water at week 5 were more than six times greater in control-fertilized plants than in those that received a low-P CRF, which may have been a result of the greater urea-N content or the heterogeneous nature of the low-P CRFs. Lower water-extractable pore-water P and N indicate less environmental risk and potentially increased crop efficiency. Our results suggest low-P CRFs can be used to produce certain economically important ornamental nursery crops successfully without sacrificing quality; however, early adopters will need to evaluate the effect of low-P CRFs on crop quality of specific species before implementing on a large scale.

Interspecific differences in root foraging precision cannot be directly inferred from species' mycorrhizal status or fine root economics

Nutrient acquisition in plants can be represented by a suite of intercorrelated root traits such as root diameter, nitrogen content, root tissue density and specific root length. However, it is unclear how a plant's ability to precisely forage for nutrients in a heterogeneous soil environment (i.e. the precision of placing roots into nutrient‐rich areas) relates to these traits. Mycorrhizal symbiosis also affects the relationship between the fine root traits and root foraging precision because fungal hyphae may be used for foraging instead of roots. Hypotheses matching high root foraging precision with low mycorrhizal colonization or ‘fast' acquisitive strategies of plants have been raised based either on data from tree species or a limited number of herbaceous species.To test these hypotheses, we compiled data quantifying the experimentally measured degree to which root biomass responded to patchy substrate nutrient concentrations (i.e. root foraging precision) for 123 herbaceous grassland species using a partial meta‐analysis. We tested root foraging precision relationship with root traits involved in nutrient acquisition and mycorrhizal symbiosis (root diameter, specific root length, root tissue density, root tissue nitrogen content and mycorrhizal colonization). The root foraging precision data came from four different pot experiments, and the trait data were extracted from publicly available trait databases. We used a phylogenetically informed approach in order to detect the degree of conservation of the relationships.We found that root foraging precision was not significantly correlated with other fine root traits and mycorrhizal colonization. Thus, it appears unrelated to the main dimensions of the nutrient acquisition space of herbaceous species, namely acquisitive–conservative strategy and outsourcing of acquisition to the fungi. Also, we found only a very weak phylogenetic signal in root foraging precision of 123 species. Our results suggest that root foraging precision constitutes another distinct, evolutionarily independent dimension in herbaceous species' trait space.

Cluster root-bearing Proteaceae species show a competitive advantage over non-cluster root-bearing species.

Cluster roots (CRs) constitute a special root adaptation that enables plants to take up nutrients, especially phosphorus (P), from soils with low nutrient availability, including recent volcanic deposits. It is unclear, however, how CR species interact with non-cluster root-bearing (NCR) species, and how substrates' fertility modulates potential interactions. We experimentally assessed the net interaction between CR and NCR species using two substrates of contrasting fertility: nutrient-rich nursery mix and tephra (low P availability). We planted seedlings of two southern South American (SSA) Proteaceae, CR species and two NCR Nothofagus species in pairs (conspecifics and heterospecifics) and as singles. We analysed the effect of seedling neighbours on survival, growth performance (e.g. total biomass and leaf area) and leaf and substrate nutrient concentrations (including manganese, a proxy for P-acquisition efficiency through CR activity) using the relative interaction index. After three growing seasons, we found that (1) Proteaceae species had fewer CRs and lower CR biomass and grew less in the tephra than in the nursery substrate; (2) Nothofagus species did not improve their survival and growth in the presence of Proteaceae species in any substrate; (3) contrary to Nothofagus, Proteaceae species improved their growth more when planted with any neighbour (including conspecifics) than when planted alone, which was accompanied by a significant accretion of leaf P; and (4) the presence of a neighbour increased the final nitrogen and P concentrations in the nursery substrate, regardless of species identity. CRs provide Proteaceae a competitive advantage over NCR species at the seedling stage, which may have important consequences for species coexistence and community structuring. The investigated SSA Proteaceae, which have not evolved in nutrient-impoverished soils, as have their relatives in south-western Australia and South Africa, improve their growth when cultivated in pairs, especially in nutrient-rich substrates.

Stoichiometry controls asymbiotic nitrogen fixation and its response to nitrogen inputs in a nitrogen-saturated forest.

Lowland tropical forests with chronic nitrogen (N) deposition and/or abundant N-fixing organisms are commonly rich in N relative to other nutrients. The tropical N richness introduces a paradoxical relationship in which many tropical forests sustain high rates of asymbiotic N fixation despite the soil N richness and the higher energy cost of N fixation than of soil N uptake. However, the mechanism underlying this phenomenon remains unclear. Our study aims to test this phenomenon and examine potential mechanisms of nutrient concentrations vs. substrate stoichiometry in regulating N fixation using multiple linear regression models. We hypothesized that the rates of asymbiotic N fixation would be low in an N-rich forest under N deposition and substrate stoichiometry would explain the variation in N fixation better than nutrient concentrations. We conducted a chronic N-addition experiment in an N-saturated tropical forest in southern China and measured the N fixation rates, carbon (C), N, and phosphorus (P) concentrations, and stoichiometry in different substrates (soil, forest floor, mosses, and canopy leaves). Total N fixation rates were high (10.35-12.43kg N·ha-1 ·yr-1 ) in this N-saturated forest because of the high substrate C:N and N:P stoichiometry (which explained 13-52% of the variation in N fixation, P<0.037) rather than substrate nutrient concentrations (P>0.05). Atmospheric N deposition (34-50kg N·ha-1 ·yr-1 ) failed to down-regulate asymbiotic N fixation in this forest possibly because the N deposition rate was insufficient to inhibit N fixation or N deposition maintained high N fixation rates by increasing C sequestration in the substrates. Our N-addition experiment showed the insensitivity of N fixation in all the tested substrates to low N addition (50kg N·ha-1 ·yr-1 ); however, medium and high N addition (100-150kg N·ha-1 ·yr-1 ) stimulated the moss and foliar N fixation because of the increases in substrate C:N stoichiometry (which explained 30-34% of the variation in N fixation, P<0.001). Overall, our results emphasize the importance of substrate (particularly mosses and foliage) stoichiometry as a driver of asymbiotic N fixation and sustained N richness in lowland tropical forests.

Gaussian process emulation of an individual-based model simulation of microbial communities

The ability to make credible simulations of open engineered biological systems is an important step towards the application of scientific knowledge to solve real-world problems in this challenging, complex engineering domain. An important application of this type of knowledge is in the design and management of wastewater treatment systems. One of the crucial aspects of an engineering biology approach to wastewater treatment study is the ability to run a simulation of complex biological communities. However, the simulation of open biological systems is challenging because they often involve a large number of bacteria that ranges from order 1012 (a baby's microbiome) to 1018 (a wastewater treatment plant) individual particles, and are physically complex. Since the models are computationally expensive, and due to computing constraints, the consideration of only a limited set of scenarios is often possible. A simplified approach to this problem is to use a statistical approximation of the simulation ensembles derived from the complex models at a fine scale which will help in reducing the computational burden. Our aim in this paper is to build a cheaper surrogate of an individual-based (IB) model simulation of microbial communities. The paper focuses on how to use an emulator as an effective tool for studying and incorporating microscale processes in a computationally efficient way into macroscale models. The main issue we address is a strategy for emulating high-level summaries from the IB model simulation data. We use a Gaussian process regression model for the emulation. Under cross-validation, the percentage of variance explained for the univariate emulator ranges from 83–99% and 87–99% for the multivariate emulators, and for both biofilms and floc. Our emulators show an approximately 220-fold increase in computational efficiency. The sensitivity analyses indicated that substrate nutrient concentration for nitrate, carbon, nitrite and oxygen as well as the maximum growth rate for heterotrophic bacteria are the most important parameters for the predictions. We observe that the performance of the single step emulator depends hugely on the initial conditions and sample size taken for the normal approximation. We believe that the development of an emulator for an IB model is of strategic importance for using microscale understanding to enable macroscale problem solving.

Effects of pH, Photoperiod, and Nutrient on Germination and Growth of Calymperes erosum C. Muell. Gemmaling

Effects of pH, photoperiod, and substrate nutrient concentration on the rate of germination of the gemmae and primary protonema growth of Calymperes erosum C. Muell. were studied. There was a statistically significant difference in germination of C. erosum gemmae and protonema growth among the different substrate pH levels, photoperiod treatments, and substrate nutrient conditions, respectively (P&lt;0.01). Gemmae germination and protonemal growth peaked at pH 4 and 5. Protonemal growth was retarded at pH 2, 3, 6, and 7. No germination was observed in continuous darkness. Germination and protonema growth increased significantly (P&lt;0.01) within the first 3 and 6 hours of daylight but not again until after 9 and 12 hours of exposure, respectively. No statistical (P&gt;0.05) increase in germination and protonemal growth was observed when the nutrient concentration was increased from 25% to 200%. Results indicate the moss is adapted to low nutrients and that it may germinate well at substrate pH as low as 2 howbeit the probability of establishment will remain limited until pH levels improve to 4 or 5. Furthermore, the moss is able to achieve net photosynthetic carbon gain during morning hours. Recovery from photoinhibition is likely by evening.

(73) Effect of Media on Growth of Euphorbia pulcherima `White Star'

Euphorbia pulcherima Willd. ex Klotzsch (poinsettia) are grown commercially in all 50 states. This experiment was conducted to find a suitable media for cultivating `White Star' poinsettia under natural day-length conditions in Orono, Maine. The growth, morphology, and foliar and substrate nutrient concentration of `White Star' poinsettia was evaluated in three different media formulations (Promix®, Metromix-560®, and a 1:1 v/v mixture of Promix® and Metromix-560®). Results indicated minimal variability in overall plant height, but there were significant differences in the canopy area. Canopy area was greatest for plants grown in Promix® followed by a combination of Promix® and Metromix-560®. Plants grown in Promix® recorded the highest fresh weight (170.6 g). Bract area was statistically insignificant among the three treatments. Nutrient status of the media varied widely and was significant for nitrate–nitrogen, phosphorus, soluble salts, iron, calcium, magnesium, manganese, sodium, sulfur, and zinc. Foliar analysis revealed that nutrient concentrations also significantly differed across treatment media. Optimum media pH for growing poinsettia ranges from 6.0 to 7.5. Media pH for Promix® was 5.9, which was significantly higher than Metromix-560® (4.65) and Promix® + Metromix-560® (1:1 v/v; 5.3). In spite of significant differences in foliar and substrate nutrient concentrations, overall plant growth remained the same.

WULPAK USED AS A MULCH OR AN AMENDMENT FOR NURSERY POTTING SUBSTRATES

Wulpak is a pelleted waste by-product derived from wool products manufacturing litter. It contains no manure or compost although it contains significant plant available nutrients. Preliminary reports suggest that mulching the top of container grown nursery crops provides a weed, moss and algae barrier and acts as a starter fertilizer by enhancing green color and stimulating new growth. To evaluate the usefulness of Wulpak, two studies were conducted. The objective of the first study was to compare the effect of supplemental fertilizing and use of Wulpak as a top mulch compared to incorporation into the potting substrate on plant growth, foliar and substrate nutrient concentrations. The objective of the second study was to evaluate Wulpak compared to PennMulch, a pelleted newspaper product, applied at two mulch depths for control of common nursery weeds. After 70 days, petunias were larger when top-dressed with supplemental Controlled Release Fertilizer (CRF) compared to the standard pine bark substrate or the Wulpak mulch or incorporation-only treatments. Tissue N was not significantly different among any treatments. Tissue P was higher in all Wulpak mulch and incorpation treatments compared to the pine bark standard. Leachate pH was consistently lower in the Wulpak top mulch treatments. Common groundsel and horseweed were controlled by all mulch treatments; although, after three months some common groundsel emerged in the 0.6 cm PennMulch pots. Spotted spurge and longstalked phyllanthus were controlled by both depths of Wulpak and by 1.3 cm PennMulch, but not by 0.6 cm PennMulch. Crabgrass was controlled only by the 1.3 cm Wulpak treatment. INTRODUCTION Wulpak is a pelleted waste wool by-product derived from wool products manufacturing litter. It contains no manure or compost although manufacture claims indicate that significant plant nutrients are available. The product is available in the US from Wilbro Inc., Norway, S.C. 29113, under an import agreement with APT Marketing, in Lincoln, UK. Preliminary reports suggest that mulching the top of container grown nursery crops provides a weed, moss and algae barrier and acts as a starter fertilizer by enhancing green color and stimulating new growth. In 1999, Wulpak was a new product in the US and was sold to nursery operators with only limited guidelines for its use. To evaluate the usefulness of Wulpak as a mulch on the surface of containers, two studies were conducted. The objective of the first study was to compare the effect of using Wulpak as a top mulch or as an addition to the potting substrate on plant growth, foliar and substrate nutrient concentrations. The objective of the second study was to evaluate Wulpak and PennMulch applied at two depths for control of common nursery weeds. Proc. IS on Growing Media Eds.: Alsanius, Jensen & Asp Acta Hort 644, ISHS 2004

The Ammophila decline: A field experiment on the effects of mineral nutrition

American beachgrass (Ammophila breviligulata) is a pioneer plant on coastal dunes of northeastern North America, where it forms dense, monospecific stands on the foredune. Although both plant and population growth are active on the front of the foredune, stand decline sometimes occurs on the back. Several hypotheses have been proposed to explain this phenomenon. The aims of the present study were to assess the effects of mineral nutrition on the performance of adult A. breviligulata plants. In a field experiment, the response of A. breviligulata to fertilizer addition was determined on the front (in a vigorous stand) and on the back (in a decline zone) of the foredune at the Dune du Sud, Îles de la Madeleine, Québec. There were differences in substrate nutrient concentration between positions on the foredune at the beginning of the growth season: potassium was somewhat higher on the front, and nitrogen on the back of the foredune in the decline zone. However, these differences were slight and not biologically significant. On the control plots, root mass density was higher on the back than on the front of the foredune. Fertilizer addition increased the density and the mass of A. breviligulata shoots both on the front and the back of the foredune. Plants in the decline zone responded strongly to nutrient addition and performed better than those in the control plots on the front of the foredune. Thus, it seems that fertilizer addition largely overtook the effect of the factor(s) responsible for the decline. Because there were no biologically significant differences in substrate nutrient concentration between the front and the back of the foredune, and because root mass density was higher on the back (in the decline zone) than on the front of the foredune, we suggest that the decline might be associated with a lower efficiency of the roots to absorb nutrients. This might be related to differences in mycorrhiza infections between the back and the front of the foredune.

Bedding Plant Growth in Greenhouse Waste and Biosolid Compost

Growth of `Oasis Scarlet' begonia (Begonia ×semperflorens-cultorum Hort.) and `Super Elfin Violet' impatiens (Impatiens wallerana Hook. f.) was compared in substrates containing compost made from used greenhouse substrates and yard trimmings (GHC) and in compost made from biosolids and yard trimmings (SYT). Treatments consisted of 100% compost (GHC or SYT) or compost combined with control substrate components at 60%, 30%, or 0%. Substrates containing SYT compost produced significantly larger begonia and impatiens plants than substrates containing GHC compost. Higher initial substrate nutrient concentrations in substrates containing SYT probably prompted increased begonia and impatiens growth because substrates containing SYT compost had significantly higher initial soluble salt, nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg) concentrations than substrates containing GHC compost. Begonia and impatiens shoot dry mass and size linearly increased as the percentage of SYT compost in the substrate increased from 0% to 100%. However, no difference in begonia or impatiens growth was observed among the different percentages of GHC compost. Initial soluble salt, N, P, K, Ca, and Mg concentrations also linearly increased as the percentage of SYT increased while only initial P, K, and Ca concentrations linearly increased as the percentage of GHC increased.

Timing is Crucial for Plug Seedling Substrate Testing

Many plug seedling growers complain about the inadequacy of substrate testing as a measure of nutritional status because results are too variable. We conducted two experiments to test a model system of sampling substrate at a set time after fertilization. Petunias (Petunia×hybrida Hort. ex Vilm. var. multiflora `Primetime White') were grown in 288-cell plug trays. Six fertilizer regimes were used consisting of a factorial arrangement of three fertilizer cycles (at each, every other, and every third irrigation) and two leaching fractions (0% and 20%). Fertilizer or water was applied at 0900 HR daily, and then 24 hours later in Expt. 1, and 1 hour later in Expt. 2, substrate solutions were sampled and analyzed. Samples taken after waterings were used to assess the dilution and leaching effects of water on substrate nutrient concentrations. In Expt. 2, additional substrate samples were taken at various hours after fertilizing to test the effect of plant depletion of the substrate. Substrate nutrient concentration curves constructed from data drawn at a fixed time after fertilizations, but not after waterings, were logical and could be interpreted. When data from a fixed time after fertilizations and waterings were plotted together, the curves could not be interpreted. Data from samples taken at various hours after fertilization in Expt. 2 revealed large reductions in concentrations, often after only 4 hours. Overall, leaching and dilution effects from watering in combination with the increased time span from fertilizing to sampling resulted in nutrient concentrations that could not be interpreted. Substrate testing can be effective for plug seedling production, but samples need to be taken 1 to 2 hours after fertilizations.

Spatial and Temporal Patterns of Substrate Physicochemical Parameters in Different-aged Barrier Island Marshes

Physicochemical substrate parameters were measured monthly from June to October 1990 in two young and two old barrier island marshes off the eastern shore of Virginia. Porewater salinity, substrate redox potential (EH), organic matter content, and sediment grain size were measured at three depths at high marsh and low marsh stations of all four sites. Porewater ammonium and phosphate, and extractable ammonium were also measured at one old and one young marsh site. Higher sand content, lower organic content, and lower elevation of the young sites relative to the old sites was representative of differences in development time between the different-aged sites. Porewater salinity peaked in mid-summer at higher levels at the old sites relative to the young sites and was higher at the high marsh stations compared to the low marsh stations of both old sites and one young site. Substrate EH was higher at the young sites, presumably as a function of better drainage related to a coarser-grain size and a steeper topographic slope relative to the old sites. Nutrient pools increased throughout the growing season in both the young and old sites, but peaked at higher levels in the old marsh below 10 cm which was consistent with the finer-grain size and higher organic content at depth of the latter site. Differences in physical substrate characteristics, EH, and nutrient pools, found in this study, generally agree with other age comparison studies which are usually between young, created marshes and older, natural marshes. Created marshes have been shown to develop inorganic nutrient pools comparable to established, natural marshes in 2-15 years. The results of this study, representing few comparisons of substrate nutrient concentration in natural, different-aged marshes, demonstrated that nutrient pools are comparable at 10 cm between 10-13-year-old marshes and marshes whose age is most likely in the hundreds of years. Nutrient pools at 30 and 50 cm of young marshes take longer than 10-13 years to reach levels comparable to older marshes at the same depths.

Composted Turkey Litter: I. Effect on Chemical and Physical Properties of a Pine Bark Substrate

Abstract Cotoneaster dammeri C.K. Schneid. ‘Skogholm’ and Hemerocallis sp. ‘Red Magic’ plants were potted into a pine bark substrate amended with 0, 4, 8, 12, or 16% (by vol.) composted turkey litter and were grown under 1-, 2-, or 3-day irrigation frequencies. Compost increased container capacity and available water 12-16% and 17-30%, respectively, compared to pine bark alone (0% compost). Unavailable water and bulk density increased with increasing compost rate, while air space decreased. Total porosity was unaffected by compost addition. Substrate solutions were extracted from the ‘Skogholm’ cotoneaster containers via the pour-through nutrient extraction method at 0, 18, 36, 54, 78, and 102 days after initiation. Ammonium, NO3, P, K, Ca, Mg, and micronutrient substrate solution concentrations increased with decreased irrigation frequency due to decreased leaching. Substrate nutrient concentrations and pH increased with increasing rate of compost addition. Compost provided adequate nutrient supplies throughout the growing season except for K and micronutrients which were depleted after day 78.

The growth of the extramatrical mycelium of ectomycorrhizal fungi and the growth response of Pinus sylvestris L.

summaryNine ectomycorrhizal fungi have been studied for their effect on the growth of Pinus sylvestris L. seedlings. The plants were kept growing for six months in root chambers with a changeable volume. All seedlings were cultivated under conditions of low substrate nutrient concentrations and they became strongly infected within a short time. We demonstrated the existence of an important negative correlation between the extent of the fungal development and the growth of the host plants. In most studies this reduced growth is attributed to an energy drain by the fungus. Fungi producing large amounts of fungal tissue are more energy consuming than species which only develop a sparse mycelium. However we suggest that also nitrogen acquisition by the plants might be altered by the fungus. Certain fungi probably retain a considerable amount of nitrogen for their own growth, thus reducing the amount transported to the host plant. A decreased N transport finally results in a slower growth. In this study the extramatrical mycelium in the rooting substrate was determined by wet oxidation and by nitrogen determination. This component of the fungal biomass showed the biggest variation among the different mycobiont species. The results are discussed in relation to the culture technique employed.