Effects of media on early‐season sweet potato transplant production in heated beds

‘Georgia Jet’ sweet potato transplants were produced in heated beds to determine the effects of aged pine sawdust and builders’ sand (traditional media) and fresh and aged pine bark, and fresh pine sawdust (alternative media), on early‐season transplant production and media characteristics. At the first harvest, higher transplant numbers were obtained with the fresh pine sawdust or pine bark (mean 1,053 transplants/m²) than with the other media (mean 619 transplants/m²). Transplant fresh weights at the first harvest responded in a similar manner. The total early‐season number of transplants obtained with fresh pine bark (1,455 transplants/m²) was also greater than the total number of transplants obtained with the traditional media and aged pine bark (mean 951 transplants/m²), but not greater than the total number of transplants obtained with fresh pine sawdust. Mean lengths and weights of transplants obtained with the alternative media were at least as great as the values obtained with transplants grown in the traditional media. Highest media pH values were obtained with builders’ sand; the pH values of the fresh pine media were less acidic than the pH values of the aged pine media. Lower volumetric water contents and greater fluctuations in temperature were obtained with builders’ sand than with the pine media. Media had no effect on the percentage of intact roots at the end of the experiment.     

Lime applications increase extended sweetpotato transplant production in heated beds 1

This experiment was conducted to determine the effects of aged pine media (sawdust and bark) and lime amendments (0.0, 2.2, and 4.4 kg/m³) on the production of ‘Georgia Jet’ sweetpotato [Ipomoea batatas (L.) Lam.] transplants at four harvests. At the first harvest, transplant production with aged pine sawdust and aged pine bark increased quadraticaly and linearly, respectively, with increasing lime rates. Aged pine media did not differ in their effects on transplant number or mean transplant weight and length at the early (first two harvests) or extended (four harvests) harvest periods. Transplant numbers increased linearly, but mean transplant length decreased linearly with lime application during both periods. A reduction in mean transplant weight was also observed. The results of this experiment provide evidence that the positive effect of amending aged pine sawdust and bark with lime continues through an extended harvest period. Transplant production, however, decreased considerably following the second harvest. Greatest early‐ and extended‐season transplant yields were 1840 and 2200 transplants/m², respectively. Media pH or leaf mineral nutrient concentrations did not adequately reflect the yield responses.     

Lime applications to aged pine media increase early‐season sweet potato transplant production in heated beds

Aged pine sawdust and bark are likely to be the most widely used media for sweet potato transplant production in heated beds in north Alabama. Transplant production in these media, however, may be limited by acid conditions. This experiment was conducted to determine the effects of the application of lime (0.0, 2.2, and 4.4 kg/m³) on early‐season production of ‘Georgia Jet’ sweet potato transplants. Differences in transplant yield and quality due to media were not obtained at the first harvest, but heavier total early‐season transplants were obtained with aged pine bark than with aged pine sawdust. At the first harvest, the highest transplant number (936 transplants/m²) and weight (1.685 kg/m²), and the greatest mean transplant length (23.4 cm) were obtained with 2.2 kg/m³ of lime, but the total early‐season transplant numbers increased linearly from 1025 to 1154 transplants/m² with the addition of lime. Total early‐season transplant quality parameters, however, did not respond to the addition of lime in the same manner. Mean transplant weight decreased from 2.31 to 2.17 g with the addition of lime, and greatest mean transplant length was obtained with 2.2 kg/m³ of lime. High media pH and petiole Ca and Mg concentrations were also obtained as a result of the lime applications.     

Prediction of water‐retention of milled pine bark‐sand potting media from laboratory analyses of individual components

Abstract

A mathematical equation which estimates water‐retention of synthesized milled pine bark‐sand pottinq media from laboratory analyses of each medium component was formulated and tested. The equation is the weighted sum of water retained by each component at a specified tension level. Media samples were sequentially subjected to 0‐, 10‐, 50‐, and 100‐cm water tension for 72 hours. Regression equations describing measured and estimated water retention at each pressure level increased linearly with increasing volumetric percent bark. The two regression equations corresponding to each tension level were not statistically different indicating that the equation for estimating water retention is reliable with synthesized pine bark‐sand media.     

Cation exchange capacity of two‐component container media predicted from laboratory analysis of components

Abstract

A mathematical equation predicting cation exchange capacity (CEC) of pine bark‐sand container media from CEC of the individual components was formulated. The equation is the weighted sum of milliequivalents contributed by each component and is corrected for shrinkage due to mixing of components. Both measured and predicted CEC increased linearly with increasing percent volumetric bark in pine bark‐sand media. Regression equations describing measured and predicted CEC were not statistically different. The predictive equation was also tested on 6 non‐synthesized 2‐component media prepared from peat moss, perlite, pine bark, vermiculite, and sand. No statistical differences between measured and predicted CEC were obtained.     

Leaf mineral nutrient concentrations or media pH affect Georgia Jet sweetpotato transplant number,length, and weight 1

The results of four experiments were combined to determine the relationships between leaf mineral nutrients or media pH and sweetpotato transplant production. The relative number of transplants and the relative mean transplant lengths or weights were determined by comparing the values obtained with unamended aged pine sawdust, a traditional medium. These values were regressed against leaf mineral concentrations and media pH. There was no relationship between relative transplant production and leaf nitrogen (N), potassium (K), or manganese (Mn) concentrations. Compared to sufficiency ranges for nearly mature sweetpotatoes, concentrations of N and K were low and Mn was sufficient. An upper value of 1210 mg/L leaf iron (Fe) was obtained for relative mean transplant weight, but concentrations of this mineral were not associated with relative transplant numbers or relative mean transplant lengths. Leaf calcium (Ca) and magnesium (Mg) concentrations were related to all three transplant characteristics directly, or indirectly through possible effects on leaf phosphorus (P) concentration or media pH. Compared to the established sufficiency ranges for nearly mature sweetpotato plants, Ca and Mg concentrations were low, P and Fe concentrations were sufficient, and zinc (Zn) concentrations were high.     

Phosphorus immobilization in wood waste‐based potting media

Abstract

Microbially induced nitrogen (N) immobilisation in potting media is accompanied by immobilisation of soluble phosphorus (P), with the P/N ratio of the immobilised elements being about 0.15. Fertiliser N applied to counter N immobilisation should be accompanied by this amount of soluble P if plants are not to suffer from P deficiency. Essentially none of the immobilised P in potting media that contained aged pine bark or eucalypt sawdust was available for short‐term growth of ‘Giant Butterfly’ pansies or Hakea francisiana subsequently grown in them. One implication of these results is that the N drawdown test for potting media will underestimate N requirements if P is not included in the charging solution.     

Forms and extractability of manganese in potting media

Abstract

Sequential extraction of pine bark medium alone and after amendment with either manganese sulfate (MnSO₄), composted rice hulls, or soil showed that at pH 5.5–7.0 most of the manganese (Mn) exists in a form that is extracted by acidic hydroxylamine hydrochloride, and which could therefore be in oxide or strongly‐bound forms. Acidification to pH 4.5–5.0 transferred large amounts of this ‘oxide’ Mn into ‘readily available’ and ‘weakly adsorbed’ fractions. Similar extractions of Sitka spruce bark showed that most of its Mn was extracted by weak cationic reagents ('readily available’ and ‘weakly adsorbed’ fractions). Growth of oats in pine bark, peat, and eucalypt sawdust media, with and without MnSO₄ amendment, lowered the amounts of Mn in ‘readily soluble’ and ‘weakly adsorbed’ fractions and caused some loss of ‘oxide’ Mn. Comparison of data for Mn extracted by 2 mM DTPA (1:1.5 v/v) with Mn in sequential fractions showed that DTPA dissolves some ‘oxide’ Mn. The data further suggest that up to about 36 mg/L DTPA‐extractable Mn would not be toxic to most plants growing in media of pH 6.0, but 60 mg/L DTPA‐extractable Mn may be if the medium pH falls below 5.5.     

Effects of salinity and alkalinity on pansy and impatiens in three different growing media

The quality of irrigation water used for greenhouse crop production can strongly influence plant growth. However, the effect on plant growth is probably a combination of water quality and the type of growing media used. To determine the effect of saline and alkaline irrigation water on plant growth and nutrition, pansy and impatiens were grown in peat, peat:pine bark, and pine bark media under standard greenhouse conditions. Salinity treatments of 0, 100 and OmgL^‐1 NaCl: CaCl₂ and alkalinity treatments of 0, 100, 200, 300, and 400 mg L^‐1 NaHCO₃ were applied at every irrigation. Salinity levels at 100 mg L^‐1 and greater caused necrosis of leaf edges, upward curling of leaves, and reduced flower number for pansy. Treatment symptoms for impatiens were reduced growth, general chlorosis, and reduced flower number. These treatment symptoms increased in severity for plants grown in pine bark. Alkalinity levels at 200 mg L^‐1 and greater caused decreased flower number, necrosis of leaf edges, and downward cupping of leaves of pansy. Treatments symptoms of impatiens were general chlorosis, water‐soaked appearance of leaves and leaf abscission. Elemental concentrations of sodium (Na⁺), chloride (Cl), calcium (Ca⁺⁺), magnesium (Mg⁺⁺), and potassium (K⁺) varied in media solution and tissue with symptom and treatment.     

Effects of hardwood sawdust in potting media containing biosolids compost on plant growth,fertilizer needs,and nitrogen leaching

Abstract

Biosolids compost is used in media to grow potted plants. Nitrogen (N) in media leachate may contribute to nitrate (NO₃‐N) contamination of surface or ground water. Addition of sawdust to potting media containing biosolids compost will increase the carbon (C) to nitrogen ratio and could prevent N leaching without adversely affecting plant growth. A control medium containing 0% sawdust (v/v), 30% perlite, 50% municipal biosolids compost, and 20% sand was modified to contain either 10, 20, or 30% (v/v) fresh hardwood sawdust. The sawdust replaced either 1/3, 2/3, or all of the perlite in the control medium. Slow release fertilizer, slow plus quick release fertilizer, or no fertilizer was added to each of the four media to determine how the sawdust affected fertilizer needs. Coreopsis (Coreopsis grandiflora L.) and Rudbeckia (Rudbeckia hirta L. ’Goldstrum') were grown in pots for five months. Leachate was tested for NO₃‐N and ammonium N (NH₄‐N). Increasing amounts of sawdust produced no differences in growth of Coreopsis and few differences in the growth of Rudbeckia. The addition of slow or slow plus quick release fertilizer had little effect on the growth of Coreopsis and a greater effect on the growth of Rudbeckia. Sawdust and fertilizer had no effect on the leaching of N. Nitrogen leached primarily as NH₄‐N during the first four weeks of the experiment.     

Container medium characterization by scanning electron microscopy and comparison with a Monte Carlo computer simulated medium

Abstract

A 1:1 by volume pine bark and sand containermedium was embedded with Spurr's epoxy resin and cross‐sectioned for SEM characterization of particle distribution. A Monte Carlo computer simulated medium was built with spheres of the same particle size distribution as the pine bark and sand grains used in the experiment. Cross‐sections from the simulated systems were compared with actual experimental data and good agreement was obtained. SEM makes it possible to analyze particle and pore distribution of container media. Computer simulation provides a good approximation of container medium structure and may prove useful in estimating properties of container medium mixtures.     

Use of Spent Mushroom Substrate for Growing Containerized Woody Ornamentals: An Overview

There are substantial environmental and economic benefits to be gained by recycling spent mushroom substrate (SMS). Researchers throughout the world have grown many types of crops with SMS but information with ornamental nursery crops is sparse. High salt levels in SMS is largely responsible for its restricted use in agriculture. Investigations showed that many ornamental woody species grew well in 6-liter (2-gal) regular nursery containers amended with different proportions of SMS (33%, 67%, and 100% by volume) mixed with bark. Test species were: cotoneaster (Cotoneaster dammeri ‘Coral Beauty’); deutzia (Deutzia gracilis); dogwood (Cornus alba and C. alba ‘Argenteo-marginata’); forsythia (Forsythia × intermedia ‘Lynwood’); juniper (Juniperus sabina ‘Blue Danube’ and J. virginiana ‘Hetzii’); ninebark (Physocarpus opulifolius); potentilla (Potentilla fructicosa ‘Red Ace’); privet (Ligustrum vulgare); rose (Rosa ‘John Franklin’); and weigela (Weigela ‘Bristol Ruby’ and W. florida ‘Variegata Nana’). Despite variable species response, there was little relationship of growth performance to: source of SMS (different farms, fresh or aged, leached or unleached); initial or subsequent salt levels in the media; chemical or physical characteristics of the media, including increasing shrinkage with increasing amounts of SMS; or contents of leaf nutrients. Plants of all species, except privet, achieved marketable size and quality at harvest. Time-course studies demonstrated that rapid leaching of undesirable high salt levels from the containers was the key to our successful results. In further studies which evaluated a wider range of amendment combinations (peat, bark, and sand) with SMS included in amounts (25% or 50%) more desirable in commercial container nursery practice, all SMS amended media promoted excellent growth of nursery crops. Minimal shrinkage was obtained with a medium consisting of 25% sand, 25% SMS, and 50% peat or bark.     

Composts as Media Constituents for Vegetable Transplant Production

The use of compost with high salt concentration was evaluated, under commercial conditions, as a potential growing media constituent for vegetable transplant production. Two composts were prepared from sweet sorghum bagasse, pine bark, and either urea (compost A) or brewery sludge (compost B) as N source. Three vegetable species — broccoli (Brassica oleracea), tomato (Lycopersicum esculentum), and onion (Allium cepa) with different tolerance to salinity were used. Eleven substrates were formulated and tested: a control consisting of a moss peat-based commercial substrate; compost A; compost B; and, eight mixtures containing 33 or 67% by volume of each compost with either raw peat moss or commercial substrate as diluent. All the substrates prepared had suitable physical, physicochemical and chemical properties for use as growing media, except for the electrical conductivity (ranging from 3.20 to 13.21 dS m^?1) which was above the reference levels for soilless cultivation. Broccoli was the least affected by substrate salinity whilst tomato was the most. Onion transplants had an intermediate response to saline conditions. Tomato seed germination was markedly reduced when compost A, with a higher salt concentration, was used at a rate higher than 67%. Media prepared with either of the composts, and mixed with either a commercial substrate or peat in a rate up to 67%, did not cause any detrimental effect on the growth and nutritional status of broccoli, tomato and onion transplants, despite the high initial salinity of the substrates. These composts appear to be acceptable substitutes for Sphagnum peat in seed sowing mixtures.     

Prediction of H‐ion activity of two‐component potting media from analysis of components

Abstract

A mathematical equation which predicts H‐ion activity (HA) of container media from laboratory analysis of components was devised and tested. The equation is based on the weighted sum of HA contributed by each component. Both measured and predicted HA increased linearly with increasing volume percent bark in milled pine bark‐sand media. Regression equations describing measured and predicted HA were not statistically different. The predictive equation was also tested on other 2‐component potting mixtures with no statistical differences occurring between measured and predicted HA. Measured pH and pH values derived from the HA predictive equation were in close agreement.     

Physical and Chemical Changes in Container Media in Response to Bark Substitution for Peat

Physical and chemical properties of container media are important factors in controlling the supply and movement of water and nutrients for nursery plant growth. The objectives of this study were to evaluate the physical and chemical properties and quality of media formulated with systematic substitution of composted pine bark (bark) for sphagnum peat (peat) in the presence of sand. Ten formulations were prepared that contained 40-90% bark, 0-50% peat, and 10 or 20% sand by volume. Increasing the percentage of bark increased the percentage of coarse particles, and linearly decreased the medium-sized particles in media in either 10% or 20% sand. Increasing the percentage of bark in the media significantly decreased water holding capacity, whereas bulk and particle densities and total porosity were influenced by the interaction of bark x peat x sand. Increasing the percentage of bark increased electrical conductivity and total C, P, K, Ca, Fe, Cu and Zn. Availability of nutrients were also increased by increasing percentages of bark. Substitution of bark for peat did not influence the pH of the formulated media. Our results suggest that formulated media with 70 to 80% composted pine bark and 10 to 20% peat (V/V) exhibited physical and chemical properties considered optimum for the growth of container nursery plant crops.     

Effect of fresh bark media on phosphorus status of tomato plants1

Abstract

Phosphorus status of tomato (cv Floradel) was determined in two experiments where plants were grown in fresh or aged softwood bark or a control medium (perlitetsand, 3:1). The P concentration of plants grown in fresh bark was lower than for those grown in other media. Highly significant correlation coefficients were obtained between growth and P concentrations. The results strongly suggest that growth depression of plants grown in fresh bark is due to bark‐induced P deficiency.     

Soil testing of horticultural substrates for cyclamen and poinsettia

Abstract

The 1: 1.5 water, Spurway and saturated media extract procedures were evaluated for cyclamen and 1: 1.5 water extract for poinsettia growing in bark, peat and peat + soil using nutrient uptake as the criterion. In addition, the N, P, and K desirable values (DV) to give maxi Timm dry wt in two harvests and to give maximum growth rate for various growing periods, in samples taken at the start of the trial and midway through the trial, were determined using a quadratic function for both crops. The relationships between N, P and K uptake and the soil test values were generally very good, although the methods overestimated N uptake and underestimated P uptake in bark‐relative to peat. Underestimation of P uptake in peat + soil was even greater. The initial desirable N soil test value in relation to midterm harvest (IDVM) for cyclamen in peat varied from 100–104 ppm for water, 303–312 ppm for saturated media and 44–46 for Spurway extraction. The midterm soil test value in relation to final harvest (MDVF) values varied from 125–136 ppm for water, 471–502 for saturated media and 44–53 ppm for Spurway extraction. Corresponding values in bark were generally higher. The IDVM and MDVF values using the water extract for poinsettia were 180–225 ppm and 155–215 ppm in peat and bark respectively. It was not possible to determine phosphorus IDVM values for cyclamen due to the poor fit of the response curve. The phosphorus MDVF values in peat for cyclamen were 8.1–8.8 ppm for water, 24.5–26.7 ppm for saturated media and 3.2–3.5 ppm for Spurway extraction. The corresponding values in bark were about half of those values and even lower in peat + soil. The phosphorus MDVF values in peat for poinsettia were 14–19 ppm and in bark 4–4.5 ppm for the water extraction. It was not possible to determine K desirable values for cyclamen because of lack of adequate plant response from K application. Potassium IDVF and MDVF values for poinsettia in peat were 100–136 and 80–126 ppm respectively. The DV obtained using growth data were broadly similar to those using plant dry wt. The desirable plant nutrient levels for maximum dry wt of cyclamen at final harvest varied from 1.9–2.4% for N, 0.10–0.17% for P and 1.0–1.7% for K. The DV values for poinsettia at mid harvest were 3.6–4.6% N, and at final harvest 2.7–3.6% N and 0.18–0.37% P.     

Effects of amending Container growing media with Dolomitic limestone on the growth of Photlnia ‘Fraseri’

Abstract

The results of three years of experimentation on the effect of the addition of dolomitic lime to pine bark‐sand media shows that Photinia ‘Fraseri’ responds positively to lime additions. This response was not due to pH changes, since for two of the three years only a small change was observed in pH and lime requirement values. It is more likely that the increased growth is due to an improved magnesium environment. Not only was the magnesium content of the foliage increased with lime addition, but the K:Mg ratio was decreased to a level where potassium‐magnesium antagonism was not important.     

Carbon sequestration in forest soils: effects of soil type, atmospheric CO2 enrichment, and N deposition

Soil contains the major part of carbon in terrestrial ecosystems, but the response of this carbon to enriching the atmosphere in CO₂ and to increased N deposition is not completely understood. We studied the effects of CO₂ concentrations at 370 and 570 μmol CO₂ mol^?1 air and increased N deposition (7 against 0.7 g N m^?2 year^?1) on the dynamics of soil organic C in two types of forest soil in model ecosystems with spruce and beech established in large open‐top chambers containing an acidic loam and a calcareous sand. The added CO₂ was depleted in ¹³C and thus the net input of new C into soil organic carbon and the mineralization of native C could be quantified. Soil type was the greatest determining factor in carbon dynamics. After 4 years, the net input of new C in the acidic loam (670 ± 30 g C m^?2) exceeded that in the calcareous sand (340 ± 40 g C m^?2) although the soil produced less biomass. The mineralization of native organic C accounted for 700 ± 90 g C m^?2 in the acidic loam and for 2800 ± 170 g C m^?2 in the calcareous sand. Unfavourable conditions for mineralization and a greater physico‐chemical protection of C by clay and oxides in the acidic loam are probably the main reasons for these differences. The organic C content of the acidic loam was 230 g C m^?2 more under the large than under the small N treatment. As suggested by a negligible impact of N inputs on the fraction of new C in the acidic loam, this increase resulted mainly from a suppressed mineralization of native C. In the calcareous sand, N deposition did not influence C concentrations. The impacts of CO₂ enrichment on C concentrations were small. In the uppermost 10 cm of the acidic loam, larger CO₂ concentrations increased C contents by 50–170 g C m^?2. Below 10 cm depth in the acidic loam and at all soil depths in the calcareous sand, CO₂ concentrations had no significant impact on soil C concentrations. Up to 40% of the ‘new’ carbon of the acidic loam was found in the coarse sand fraction, which accounted for only 7% of the total soil volume. This suggests that a large part of the CO₂‐derived ‘new’ C was incorporated into the labile and easily mineralizable pool in the soil.     

The growth of tagestes erecta,petunia hybrida nana compacta and myosotis alpestris in a range of peat‐based container media

Abstract

The dry matter yield and nitrogen content of marigold (Tagestes erecta), petunia (Petunia hybrida nana compacta) and forget‐me‐not (Myosotis alpestris) plants growing in a range of peat‐based container media amended with different proportions of either sand, perlite, pumice, sawdust, bark chips or soil were studied under glasshouse nursery conditions.

Plant responses differed between species as manifested by their different correlations with measured moisture and aeration characteristics of the media. Marigold and petunia were adversely affected by excessive moisture content as demonstrated by their negative correlation with micropore water and container capacity. However, forget‐me‐not, being adapted to relatively high moisture regimes, responded adversely to increased aeration.