Two groups of soils were studied, the first being made up of twelve heavily fertilised representative soils from the European Community and the second containing fertilised and unfertilised soils for comparison. The first group demonstrate how the amount of plant available P was generally most closely related to soil P content, rather than soil chemical characteristics. However, the total adsorption capacity tends to decrease in the order moderately acid > calcareous > weakly acid. A very steep increase in solution P concentration above 60 percent saturation was observed and it was calculated that 15 to 30 years of cropping without further fertiliser P additions is required to bring some soils below this level. The second group of soils shows how long term P fertiliser additions cause accumulation of all forms of inorganic P. The comparison of a continuously fertilised soil to one which has had no P additions for three years, suggests that once soils of this type have been fertilised in excess of plant requirements, they can be cropped for several years without decreasing yield due to P deficiency. The aggregate separation indicates how selective erosion of small aggregates leads to increased loss of P in most cases. Mixing of aggregates demonstrated how some have a stronger ability to influence concentration than others and this was linked to their phosphate buffer capacity. Reducing conditions increased P release and this was linked to a combination of soil type, P content and cation release. Fertilisation has increased the available P and the ability to influence solution P most in the fraction at the greatest risk from erosion.

Anaerobic conditions resulting from flooding often lead to enhanced release of phosphorus (P) to overlying water. This study examined the effect of flooding and anaerobic conditions on soil P dynamics. A field ponding study using Scanterbury heavy clay soil (unamended, inorganic fertilizer- or manure-amended), and a laboratory incubation study using 12 soils (unamended or manure-amended) from Manitoba showed that P release to flood water under reduced conditions varied substantially. In the field ponding study, flooding and development of anaerobic conditions did not enhance P release into surface flood or soil pore water. In the incubation study, the response to flooding and anaerobic conditions ranged from a small decrease to a 15-fold increase in dissolved reactive P concentration (DRP) in flood water. Partial least squares analysis indicated that measures of degree of P saturation in soils can effectively predict DRP concentration changes in surface flood water under anaerobic conditions.

Growing interests in dietary manipulation to reduce P excretion in animal manure and P loss from agricultural soils to the environment have led to strategies such as the use of phytase in monogastric animal diets. The efficacy of phytase has been confirmed by several studies that reported its ability to hydrolyze phytate P present in grain feeds and thus, reduce manure total P. However, the solubility of manure P from phytase supplemented diets in soils is not well known, and as thus, the environmental implications of dietary P manipulation require further investigation. Two related studies were carried out in the laboratory to investigate the fate of manure phosphorus (P) from pigs fed phytase supplemented diets in Manitoba soils. The first study characterized the forms of manure P from phytase supplemented swine diets to evaluate their potential environmental impact. The seven dietary treatments fed randomly to a total of 28 growing pigs were: a positive control that contained P at the NRC (1998) recommendations (NRC), a negative control (RED) containing 0.1 percentage units reduction (about 33%) in available P from 1998 NRC recommendations, RED with 500 U of phytase kg-1 of diet (RED + P1), RED with 1000 U of phytase kg-1of diet (RED + P2), a double negative control with no added inorganic P (DNC), DNC plus 2000 U of phytase kg-1 of diet (DNC + P3) and DNC plus 4000 U of phytase kg-1 of diet (DNC + P4). The second study examined the solubility of manure P from the manure collected from the first study. Manure collected from the first study were applied at a rate of 75 kg of total P ha-1 of soil to surface samples from four Manitoba soils (0-15 cm); Osborne clay (Rego Humic Gleysol/Gleysolic Humic Vertisol), Red River clay (Gleyed Rego Black Chernozem/Gleyed Humic Vertisol), Ladywood very fine sandy loam (Gleyed Dark Gray Chernozem), and Glenhope loamy fine sand (Gleyed Rego Black Chernozem). In the first experiment, total P in feces and manure were significantly reduced (p < 0.05) with phytase addition to the diets. The labile P concentration (sum of H2O–P and NaHCO3-P) was about 71 to 89% and 77 to 89% of total P in both feces and manure, respectively. Phytase addition to the diets reduced the labile P in feces. The solubility of P was greatest in the calcareous soils amended with the manure from the DNC diets and solubility of P varied with time and extracting solutions. Although, a combination of physico-chemical properties (e.g. CEC, Exchangeable Ca2+), texture seems to play a significant role, as P solubility increased in coarse textured soils after longer period of incubation (16wks). However, our results showed that phytase supplementation in the diets of pigs did not affect the solubility of manure P in amended soils.

An extant model was evaluated to assess its adequacy for nutrient management planning for swine operations in Manitoba with regards to phosphorus (P) and nitrogen (N) excretion and the land base for the optimum spreading of manure based on P requirement of crops. Two dietary treatments were used, control diet formulated to meet the requirement of pigs for nutrients as per the recommendations of NRC (No-phytase) and a diet formulated with P level in the No-phytase diet reduced by an average of 0.1 percentage units and amended with microbial phytase at 500 FTU/kg (Phytase). Data was generated from starter to finisher pigs (10 per dietary treatment) and sows (9 per dietary treatment) to evaluate the model. The model was found to be adequate for the prediction of P outputs from starter to finisher but not sows. Model was found to be inadequate for prediction of N output.

Declining phosphate reserves and stricter regulations regarding wastewater discharge have increased the need for phosphorus removal and recovery. Crystallization is a promising option since P would not only be removed from the waste stream, but could also be recovered as struvite, a potential fertilizer. The purpose of this research was to achieve effective P removal and recovery through struvite precipitation from agricultural wastewater with minimal chemical input. It was found that raw swine manure had the potential for P removal and recovery through struvite precipitation by raising the pH through aeration without any Mg2+ amendment. This led to the development of a side-stream continuous 12 L reactor design with a novel combination of fluidized seedbed and aeration for pH increase. Synthetic feed was used to optimize the operational parameters of the reactor system. It was found that for a 100 ml/min influent rate, an aeration and recycle rate combination of 4.5 – 7 LPM and 700 ml/min was sufficient for increasing and maintaining the reactor pH from 6.7 to between 7.6 and 8.0. Significant P removal was achieved in six h runs without a seedbed (91 – 92%), while neither the struvite nor sand seedbeds improved P removal (91 – 96%). Struvite was recovered in all runs, with additional Ca2+ precipitation in the seedbed runs. Long-term runs showed that operation of the reactor was possible for an extended period of time, up to 46 h without any major adjustment. The average P removal was 85 – 88%, and precipitate collected after 24 h was found to be mainly struvite, while the final precipitate also contained calcite. This study has demonstrated the technical feasibility of an aerated crystallization reactor system for struvite removal and recovery from synthetic swine wastewater. By avoiding chemical amendments this reactor system has eliminated a significant portion of the operational costs found in comparable systems. The major obstacle for achieving system stability and consistency was scaling.

Agricultural land is widely acknowledged as a primary non-point source of nutrients that affect the health of freshwater ecosystems throughout many parts of the world. Simulated rainfall-induced runoff trials were conducted at four P amended primary field sites under annual crop cultivation and three un-amended secondary field sites during the fall of 2009 and 2010. Highly significant (P <0.001) linear relationships were observed between measures of soil P and runoff TDP (r2 = 0.20–0.43). Olsen P was as accurate as other soil test methods for predicting runoff P losses. However, site, sampling year, runoff interval and crop residue management practices also affected these relationships. In particular, the predictability of these relationships on a site by site basis, as well as from one year to the next was extremely variable (r2 = 0.00-0.86), and declined significantly as the range of STP values decreased below approximately 80-100 mg P kg-1.

The over application of manure phosphorus (P) to farmlands can lead to P build up in the soil and eventual runoff to surface waters causing eutrophication. Reducing P in manure by precipitation of struvite enables P capture and reuse as a fertilizer in the agricultural supply stream. Struvite precipitation is dictated by levels of soluble P which can be highly variable according to manure treatment and management. This research studied P forms in liquid pig manure, ways of increasing P-PO4 levels in manure from strategic storage conditions, novel struvite reactors, and the effectiveness of struvite as a fertilizer. Studies that monitored soluble nutrients during manure storage revealed that P-PO4 concentration was sensitive to pH and time. Anaerobic fermentation of manure increased P-PO4 by 2.5 fold with 12 days of storage, provided the buffering by alkalinity was low. Two different struvite reactors were operated, a batch-type system for processing lagoon supernatant and an upflow air sparged reactor that used supernatant from a rotary press solids separator. They achieved 75% and 31% total P removal, respectively. The upflow reactor operated without chemical addition at pH 6.8 to produce high purity struvite free of calcium phosphates. Costs of both reactors were comparable ($0.0139 and $0.0167/kg live pig wt) and similar to other pilot struvite reactors. Manure derived struvite was compared with pure struvite and commercial fertilizer for agronomic value in canola production. Results of a greenhouse pot experiment showed no significant difference between the two struvites despite impurities in the manure precipitate.

Greenroofs are increasingly being recognized as an effective site level best management practice (BMP) to reduce the volume of stormwater runoff in urban environments. For some water quality constituents, greenroofs can improve runoff water quality but recent studies demonstrate greenroofs are sources rather than sinks of phosphorus (P). Accordingly, further research is required to evaluate treatment technologies that improve the performance of these BMPs. This study examined the use of two engineered media types to reduce phosphorus loadings from a greenroof located on the Archetype Sustainable House at Kortright in Vaughan, Ontario. A treatment system was installed to capture and remove P in stormwater runoff using sorptive properties of an engineered media. A mass balance approach was used to evaluate pre and post-treatment water quality. Pre and post-treatment water samples were collected for 25 rainfall events from July 11, 2009 to August 22, 2010 and analyzed for soluble reactive phosphorus (SRP), total phosphorus (TP), suspended solids (SS) and total dissolved solids (TDS). Storm events ranged in return frequencies from < 2 years to 35 year periods. The results show that the greenroof was a consistent source of P. The volume weighted mean concentrations were 0.769 mg/L and 0.630 mg/L for 2009 and 2010 events, respectively. The media used in 2009 reduced SRP loadings by 32.0% and TP loadings by 25.4%. The media evaluated in 2010, reduced SRP loadings by 82.4% and TP loadings by 86.6%. The greater P removal demonstrated by the 2010 media is attributed to a higher specific surface area and increased P sorptive capacity. Results of this study will help inform the use of sorptive materials in greenroof applications and a wider range of best management practices for stormwater quality treatment.

The nutrient elements needed for the optimum growth and yield of pear trees is vitally important to the pear growers. The knowledge of the amounts and kinds of fertilizer to apply to obtain this growth could increase the production and cut the costs for these growers. Field experiments have been made on the nutritional elements needed for pears, but the results were affected by many variants, such as the availability of the elements and rainfall. The growing of fruit trees in sand with controlled nutrient solutions added had been used to obtain data not possible to obtain under field conditions. Since other factors affect the absorption of the nutrient elements in the field experiments, an experiment for the application of varied nutrient solutions on one year old Anjou pear trees, grown in sand culture, was undertaken. The purpose was to try to determine the influence that the concentration and the ratio of nitrogen and phosphorus in the nutrient solutions would have on the amount of nitrogen and phosphorus which the pear trees would absorb into the leaves. One year old pear trees were grown in a sand culture in a greenhouse through one growth period. The experiment was set up as a factrial with three levels each of nitrogen and phosphorus. The solutions were applied through an automatic system which irrigated the trees every hour. The solutions were checked daily and were changed once every week. The trees were harvested and the leaves were analyzed for nitrogen and phosphorus. The results indicated that the supply of nitrogen was adequate at all levels to support normal development of the leaves of the trees. The supply of nitrogen in the nutrient solution did not cause the percent of nitrogen in the leaves to vary by a statistically significant amount. The analysis of the variations of the percent of phosphorus in the leaves showed significant differences between treatments. The main effect of the phosphorus in the nutrient solution was to increase the phosphorus content of the leaves as the supply of phosphorus was increased. The main effect of phosphorus on nitrogen was negative at all levels. This effect was noticeable at the highest phosphorus level, but it was not statistically significant. The ability of the Anjou pear tree, to absorb both nitrogen and phosphorus from a nutrient solution with very low levels of each of the elements, implies that heavy fertilization with either of these elements may not be necessary for normal, vigorous growth; this is especially true in the case of phosphorus. / Graduation date: 1960

Thesis (Ph. D.)--University of Washington. / Bibliography: l. 97-105.