No description available.

Several hypotheses concerning the role of fishes in influencing nutrient dynamics in freshwater ecosystems were examined in Lake Memphremagog (Quebec-Vermont). Phosphorus excretion by fishes provides a negligible amount (< 0.33%) in comparison to the quantity taken up by the seston. The phosphorus pools present in the seston and fish community were approximately equal and both were twice the phosphorus content in the zooplankton. Part of this nutrient reservoir is released during the decomposition of fish carcasses. The potential is dependent upon post-spawning mortality rate, the fate of phosphorus in decomposing fish tissue, and the concentrations of allochthonous phosphorus entering the lake. Daily losses of epilimnetic phosphorus from the seston due to fish (up to 40%) and enhancement of nutrient excretion by zooplankton due to size-selective predation are important when open water fish populations are mainly planktivores. When benthic, detrital, or faculative consumers predominate, as in Lake Memphremagog, the effect of fishes on nutrient dynamics through foraging pressure is probably small.

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.

No description available.

Precipitation reactions of phosphorus (P) with Ca decrease the P fertilizer efficiency in calcareous soils. The hypothesis was that anion competition of sulphate with phosphate to precipitate with Ca will increase P solubility in calcareous soils. Initial experiments were conducted to investigate the effect of co-application of K2SO4, (NH4)2SO4, MgSO4 and (NH4)2CO3 on the solubility of monopotassium phosphate (MPP) and monoammonium phosphate (MAP) in different Manitoba soils. Co-application of sulphate salts enhanced P solubility by a factor that ranged from 6% to 44% in soils with greater exchangeable Ca and smaller acid-extractable Ca content (i.e. Osborne, Red River, Balmoral and St. Claude soil series). Solubility and solid-state speciation of P were investigated when MPP was banded with sulphate salts in both model and natural (Dezwood Loam soil series, DL) calcareous soils. The results of S K-edge X-ray absorption near edge structure spectroscopy (XANES) showed that CaSO4•2H2O was formed in DL soil when either K2SO4, (NH4)2SO4 or MgSO4 was applied with MPP. Phosphorus-31 magic-angle spinning nuclear magnetic resonance (MAS NMR) analysis showed that dicalcium phosphate dihydrate (DCPD) was formed in both soils, but the relative proportion of DCPD decreased in the presence of sulphate salts due to the formation of a new P compound. The results also showed that decreasing Ca saturation on the cation exchange complex increased the solubility and mobility of MAP in model calcareous soils and Ca played a more dominant role in forming P precipitates than Mg. According to 31P MAS NMR results, DCPD was the dominant P species in soils with 100% to 50% Ca saturation on the cation exchange complex while poorly ordered magnesium phosphate trihydrate was the prominent P phase with 70% to 100% Mg saturation. This study has demonstrated that the combination of solid state NMR and XANES provided complimentary information concerning anion competition and changes in P speciation due to the co-application of sulphate salts in fertilizer bands. Application of sulphate salts is a promising agronomic practice to enhance P solubility in soils with greater exchangeable Ca content due to the anion competition by sulphates with phosphate to precipitate with Ca.

No description available.