Craig D. Stanley

Nutrient Leaching during Establishment of Simulated Residential Landscapes.

Research evaluating nutrient losses during the establishment of plant material in mixed residential landscapes is limited. The objectives of this study were to determine the effect of vegetative cover type, compost application, and tillage on nutrient losses during the establishment of landscape plants. Twenty-four small plots constructed with subsoil fill were planted with St. Augustinegrass [ (Walter) Kuntze] and mixed ornamental species in a randomized complete block design. Plots received composted dairy manure solids at a rate of 0 or 50.8 m ha- in combination with shallow tillage or aeration. Cumulative leachate loads and flow-weighted mean concentrations of NH-N, NO + NO-N, and dissolved reactive P (DRP) were calculated periodically and annually to assess nutrient leaching from landscape plots. Higher cumulative leachate volume, inorganic N and DRP loads, and mean NO + NO-N and DRP concentrations were observed under ornamental cover during one or more study periods, which we attribute to differences in root density and shoot biomass between mixed ornamental species and turfgrass during establishment. Greater cumulative leachate inorganic N loads were reported from composted soils than from unamended soils or soils receiving only tillage or aeration. Inorganic N and DRP loads were similar in magnitude to reported leaching losses from agricultural systems. Better management of nutrients and water in woody ornamental plant beds during plant establishment is needed due to differences in plant growth habits compared with turfgrass. Nutrient content of organic amendments should be considered when applying these materials as a soil conditioner in new residential landscapes.

Phosphorus Fractionation in Core Sediments from Haihe River Mainstream, China

Sediments from Haihe River mainstream, located in Xingjiaquan, Zhangjiazui, Tianjin, were collected and examined on the basis of P fractionation. SMT (standards, measurements and testing) procedure was adopted to investigate the changes in P concentration with depth in the core sediments collected from the different sampling sites of Haihe River mainstream. The relationships among different P fractions, such as exchangeable P (Ex-P), metal oxide bounded P (NaOH-P), organic matter and grain size, were also discussed. The results indicate that in both sites the rank order of P fractions was HCl-P > Organic P (OP) > NaOH-P > Ex-P in terms of their concentration. The Ex-P represented < 4% of the sediment total P, while the NaOH-P ranged 5–21%. The calcium bound phosphorus (HCl-P) showed considerable contribution (53–80%) to the sediment total P loads. Silt/clay sized sediments exhibited significantly higher concentrations of HCl-P and Ex-P in both sites. However, coarse-sand-sized sediments exhibited significantly higher concentrations of OP in both sites and NaOH-P in Xingjiaquan. Multivariate statistics were performed to identify the factors that influenced the sediment P.

Suitability of Two Methods for Determination of Point of Zero Charge (PZC) of Adsorbents in Soils

ABSTRACT The points of zero charge (PZC) of manganese oxide (MnO2), titanium dioxide (TiO2), aluminum (Al) laterite, ferruginous (Fe) laterite, aluminum oxide (Al2O3), and a commercial activated carbon sample (AC001) were determined using acid-base potentiometric (PT) and mass titration (MT). The MT technique has been used extensively for carbonaceous materials but less for soils. In addition, little work has been done on the PZC of these metal oxides and carbon materials under similar experimental conditions concurrently. Our aim is to buttress the ease of MT usage over PT in routine laboratory analysis. The experimental PZC measured by acid-base potentiometric and mass titrations respectively were 4.97 and 4.11 for MnO2; 5.38 and 5.74 for TiO2; 4.19 and 4.08 for Al laterite; and 4.45 and 4.10 for Fe laterite. For Al2O3 and activated carbon, mass titration gave 7.53 and 8.41 respectively. Calculated standard deviations between the means of PT and MT were less than 1, and Student’s t-test at 95% confidence interval (CI) gave a P value of 0.135, suggesting that there is no significant difference between PT and MT and buttressing the reliability of the experimental procedures. In routine laboratory work, mass titration should be preferred for PZC measurement of (hydr)oxides and soil materials because it saves time.

Developing a Remediation Strategy for Phosphorus Immobilization: Effect of Co-blending, Al-residual and Ca-Mg Amendments in a Manure-Impacted Spodosol

A remediation strategy called “co-blending” was developed for rapid phosphorus (P) immobilization. Immobilization was achieved through the combination of an Al-based water treatment residual (Al-WTR) with Ca-Mg-based materials (Slag and magnesium oxide) for use in incubation and leaching experiments. Al-WTR was co-blended with Slag and MgO as “Al-WTR+Slag” and “Al-WTR+MgO,” respectively. Sequential extraction was used to delineate P species into operationally defined fractions: soluble or exchangeable, Al-Fe, and Ca-Mg-bound pools. Results from soils used in the incubation experiment showed that Al-amended material tended to sequester P bound (∼26%) to the Al-Fe pool. On the other hand, Ca-Mg-based materials tended to sorb (∼70%) of P greatly associated to the Ca-Mg pool. Amendments were applied at 2% or 20 g kg−1 as Al-WTR, MgO, and Slag and at 1%+1% or 10 g kg−1+10 g kg−1 as co-blended Al-WTR+MgO and Al-WTR+Slag, respectively, on mass basis. Results from leaching data suggest that treatment effects on pH are significant at (p < 0.0001) and also significant (p < 0.01) with weeks of leaching. A similar significant (p < 0.0001) trend was observed for effects of treatment on redox potential (Eh). However, treatment effects on weeks of leaching were not significant. Cumulative soluble P (mg) of leachate showed linear reduction (96%) from the control (without amendments) using a regression model. Potential co-blended material selected was Al-WTR+Slag (1%+1%) due to less P in leachates, moderate effect on pH, and fewer amounts of Al-WTR and Slag used compared with 2% Al-WTR and Slag, respectively. In addition, the RMSE of Al-WTR+Slag data fitted to a regression model was the least. Results suggested that the metal cations Al, Ca, and Mg tended to bind different forms of total P at any given pH. Through co-blending, less soluble P may be lost to the environment than using sorption materials independently.

Comparison of Freeze Protection Methods for Strawberry Production in Florida

Abstract During strawberry (Fragaria × ananassa) freeze protection, the standard practice is applying sprinkler irrigation on plant canopies to prevent and reduce freezing damage. This method is highly inefficient because it uses large volumes of water. The overall goal of this study was to compare the effects of freeze protection methods on water savings, and growth and fruit weight of strawberry. Treatments consisted of the following: sprinkler heads delivering 17 L∙min–1, sprinkler heads delivering 13 L∙min–1, light-weight row covers (21 g∙m–2) on the crop canopy, light-weight row covers on 60-cm-high mini-tunnel hoops, heavy-weight row covers (31 g∙m–2) on the crop canopy, heavy-weight row covers on 60-cm-high mini-tunnel hoops, and foliar application of a polymer (Desikote). There were eight freezing and near freezing nights (≤1.1 °C) at the experimental site during both seasons with a minimum air temperature of –2.8 °C. Minimum temperature inside the row covers ranged between 0.6 to 4.4 °C at the canopy level. There were significant treatment effects on early and total marketable fruit weights. The highest early marketable fruit weight was found in plots protected with light-weight row covers with hoops, heavy-weight row covers on canopy, and foliar polymer, ranging between 5.0 to 5.5 t∙ha–1. For total marketable fruit weight, using non-irrigation methods resulted in the highest fruit weight with 23.0 t∙ha–1. In conclusion, data showed that using non-irrigation techniques provided satisfactory freeze protection under the evaluated conditions and increased total marketable fruit weight, possibly due to reduced injury of fruits and flowers when using alternative techniques.