Effect of Nanoparticle Phosphate Rock and Phosphate Solubilizing Fungi on Soil P-Potential, P-Retention, Organic Carbon and Base Saturation on Cilembu’s Inceptisols

Intensive agricultural cultivation on Cilembu’s Inceptisols has become several soil properties problem for crop production. Nanoparticle phosphate rock and phosphate solubilizing fungi have ability to increase some soil properties content. The research aimed to observe the effect of nanoparticle phosphate rock and phosphate solubilizing fungi on soil P-potential, P-retention, C-organic and base saturation on Cilembu’s Inceptisols. The experiment arranged in Completely Randomized Design. The nanoparticle phosphate rock consisted of 4 levels. The phosphate solubilizing fungi consisted of 2 levels, and 2 replication. Soil P-Potential, P-Retention, C-organic, and Base Saturation were observed. The factors was observed after one month incubation on soil. Results showed that there were an interaction between nanoparticle phosphate rock and phosphate solubilizing fungi on the C-organic after one month incubation. Nanoparticle phosphate rock had affected on C-organic, P-potential and base saturation significantly, but had not affected on P-retention. Utilization of phosphate solubilizing fungi as soil ameliorant had affected significantly on P-potential and C-organic, but had not affected on P-retention and base saturation. Nanoparticle phosphate rock with a dose of 6% had the best effect on increase P-potential and base saturation

Phosphorus Retention in Lakes: A Critical Reassessment of Hypotheses and Static Models

Various hypotheses and models for phosphorus (P) retention in lakes are reviewed and 39 predictive models are assessed in three categories, namely mechanistic, semi-mechanistic, and strictly-empirical models. A large database consisting of 738 data points is gathered for the analyses. Assessing four pairs of competing hypotheses used in mechanistic models, we found that (i) simulating lakes as mixed-flow reactor is superior to plug-flow reactor hypothesis; (ii) modeling P loss as a second-order reaction outperforms the first-order reaction; (iii) P loss is better explained as a removal process throughout the lake volume than as a settling process across the sediments; and (iv) considering a fraction of P loading is associated with fast settling particles enhances lake total phosphorus (TP) predictions. Due to the systematic approach used for combining the hypotheses, some models are for the first time developed and assessed. For instance, the preeminent mechanistic model combines, for the first time, the second-order reaction hypothesis with the hypothesis that a specific proportion of P loading settles rapidly at the lake entrance. Results also showed that semi-mechanistic models outperform both mechanistic and strictly-empirical models since they take the form of a mechanistic model based on the physical representation of the lakes and utilize statistically acquired equations for unknown parameters. The best-fit model is a semi-mechanistic model that adopts the mixed-flow reactor hypothesis with a second-order volumetric reaction rate that is calculated as a non-linear function of inflow TP concentration, lake average depth, and water retention time. This model predicts 77.8% of the variability of log10-transformed lake TP concentration, which is 4.2% higher than the best mechanistic model and 0.8% higher than the best strictly-empirical model. The findings of this study not only shed light on the understanding of P retention in lakes but also can be useful for assessment of data-limited lakes and large-scale hydrological models to simulate the P cycle.

Formulation of diets for pigs based on a ratio between digestible calcium and digestible phosphorus results in reduced excretion of calcium in urine without affecting retention of calcium and phosphorus compared with formulation based on values for total calcium

An experiment was conducted to test the hypothesis that formulating diets for pigs based on a ratio between standardized total tract digestible (STTD) Ca and STTD P instead of total Ca and STTD P does not decrease Ca retention, but increases P utilization. Forty barrows (59.4 ± 3.8 kg) were individually housed in metabolism crates and allotted to 4 corn-soybean meal-based diets in a randomized complete block design with 2 blocks and 5 pigs per diet in each block. Diets were formulated using a 2 × 2 factorial design with 2 diet formulation principles (total Ca or STTD Ca) and 2 inclusion levels of microbial phytase (0 or 500 units per kg of feed). Phytase was assumed to release 0.11% STTD P and 0.16% total Ca. Diets were formulated based on requirements for total Ca and STTD P or a ratio between STTD Ca and STTD P of 1.25:1. Diets were fed for 11 d and fecal and urine samples were collected from feed provided on d 6 to 9. Interactions (P < 0.05) between diet formulation principle and phytase level were observed for Ca intake, Ca in feces, Ca absorbed, Ca retained, P digestibility, P absorbed, and P in urine. Phytase increased (P < 0.05) the digestibility of Ca in both total Ca and STTD Ca diets. Without phytase, Ca intake, Ca in feces, and Ca absorbed was greater (P < 0.05) from pigs fed total Ca diets than from pigs fed STTD Ca diets, but P absorbed, P digestibility, and P in urine was greater (P < 0.05) from pigs fed STTD Ca diets than from pigs fed total Ca diets. However, in the presence of phytase, no differences between diet formulation principles were observed in these variables. Regardless of phytase, Ca in urine was lower (P < 0.05) from pigs fed STTD Ca diets than from pigs fed total Ca diets. There were no differences in Ca retention between pigs fed STTD Ca diets and total Ca diets, but pigs fed total Ca diets retained less (P < 0.05) Ca if diets contained phytase. No differences in P retention were observed between diet formulation principles, but pigs fed non-phytase diets retained more (P < 0.05) P than pigs fed diets with phytase. In conclusion, because diets formulated based on STTD Ca contain less Ca than total Ca diets, pigs fed STTD Ca diets excreted less Ca in urine, but retention of Ca was not affected. Formulating non-phytase diets based on STTD Ca instead of total Ca increased P absorption, which confirms the detrimental effect of excess Ca on P digestibility. However, P retention was not improved if pigs were fed STTD Ca diets.

Investigating Fast- and Slow-settling Phosphorus Fractions in Lakes using Steady-state Modeling

<p>Phosphorus (P) is the key and limiting nutrient in the eutrophication of freshwater resources. Modeling P retention in lakes using steady-state mass balance models (i.e. Vollenweider-type models) provides insights into the lake P management and a simple method for large-scale assessments of P in lakes. One of the basic problems in the mass balance modeling of P in lakes is the removal of P from the lake water column by settling. A fraction of the incoming P into the lake from the watershed is associated with fast-settling particles (e.g. sediment particles) that result in the removal of that fraction of P quickly at the lake entrance. However, existing models considering a constant fraction of fast-settling TP for all lakes are shown to result in overestimation of the retention of P in lakes with short hydraulic residence time. In this study, we combine a hypothesis of the fast- and slow-settling P fractions into the steady-state mass balance models of P retention in lakes. We use a large database of lakes to calibrate the model and evaluate the hypothesis. The results of this work can be used for the improvement of the prediction power of P retention models in lakes and help to better understand the processes of P cycling in lakes.</p>

Effects of aging and transformation of Fe(III)-precipitates on the retention of co-precipitated phosphate

<p>The cycling of phosphorus in terrestrial and aquatic systems is tightly coupled to the redox-cycling of iron (Fe). The oxidation of dissolved Fe(II) in natural waters leads to the precipitation of amorphous to poorly crystalline Fe(III)-solids that can bind phosphate (P) and other nutrients as well as toxic compounds. The EU project P-TRAP is aimed at developing methods to reduce diffuse P inputs into surface waters to mitigate eutrophication, by using Fe-rich byproducts from water treatment (https://h2020-p-trap.eu/). Within this project, we study mechanistic aspects of the formation and transformation of P-containing Fe(III)-precipitates and their implications for P retention in soils and water filters.</p><p>Freshly formed Fe(III)-precipitates are metastable and can transform into more stable phases over time. This may lead to the release of co-precipitated P. In laboratory experiments, we assessed how Ca, Mg, silicate (Si) and P impact on the formation and transformation of Fe oxidation products (at 0.5 mM Fe) and their P retention in synthetic bicarbonate-buffered groundwater. The time-resolved experiments were performed in electrolyte solutions containing Na, Ca, or Mg as electrolyte cation, without or with Si (at molar Si/Fe of 1), and P (P/Fe of 0.3 and 0.05). Changes in dissolved element concentrations over time were linked to changes in the structure and composition of the Fe(III)-solids; with Fe coordination probed by X-ray absorption spectroscopy, mineralogy by X-ray diffraction, and nano-scale morphology and composition heterogeneity by transmission electron microscopy with energy-dispersive X-ray detection.</p><p>The freshly-formed Fe(III)-precipitates were mixtures of amorphous Fe(III)-phosphate with either poorly-crystalline lepidocrocite (without Si) or Si-containing ferrihydrite (with Si). Increases in dissolved P during aging were largest in Na electrolytes without Ca, Mg or Si, and were linked to the transformation of amorphous Fe(III)-phosphate into lepidocrocite with a lower P retention capacity than Fe(III)-phosphate. In Ca- and to a lesser extent Mg-containing electrolytes, the Ca or Mg stabilized the amorphous Fe(III)-phosphate and thereby reduced P release over time. The presence of Si increased initial P uptake and inhibited P release during aging by causing the formation of Si-ferrihydrite with higher P sorption capacity than lepidocrocite formed in the absence of Si. In conclusion, the extents to which P is trapped by fresh Fe(III)-precipitates and released during aging can be attributed to the individual and coupled impacts of Ca, Mg and Si on Fe(III)-precipitate structure, stability and transformation.</p><p>In continuing work, we aim to expand our work to study how organic compounds impact on the formation and colloidal stability of Fe(III)-precipitates and P retention.</p>

Kinetics and mechanism of phosphate release upon sulfidation of phosphate-containing lepidocrocite

<p>Sulfidation of Fe(III) (hydr)oxides plays an important role in the phosphate(P) cycle in oceans and lakes. P has a strong affinity to Fe(III) (hydr)oxides and can either become incorporated via coprecipitation or adsorb onto the solid’s surface. Consequently, P enters aquatic sediments often associated with Fe(III) (hydr)oxides. In the sediments, when sulfidic conditions are prevalent, the reaction of Fe(III) (hydr)oxides with sulfide can lead to the formation of Fe(II) sulfides and P release. The released P can, in turn, diffuse upwards into the overlying water and thus aggravate eutrophication in water bodies.  Although it is generally expected that P is released during the sulfidation of P containing Fe(III) (hydr)oxides, questions remain whether part of the P could be re-adsorbed onto the products of the sulfidation reaction, or trigger the formation of vivianite<sup> [1]</sup> (Fe<sub>3</sub>(PO<sub>4</sub>)<sub>2 </sub>· 8H<sub>2</sub>O). Furthermore, it is still unclear how the rates of P release are related to the progress of the sulfidation reaction.</p><p>In order to study the P dynamics during sulfidation, we performed experiments in flow-through reactors with P-bearing lepidocrocite (γ-FeOOH). The inflow solution contained sulfide and we monitored P, dissolved S(-II) and Fe(II) in the outflow to follow the progress of sulfide consumption and P release. Sulfide concentrations in the outflow of reactors containing lepidocrocite with adsorbed P tended to be lower than in the outflow of reactors with lepidocrocite but no P. Consequently, the preliminary results indicate that consumption rates of sulfide by the reaction with lepidocrocite were lower when P was present, implying that adsorbed P reduced the rates of sulfidation. At the beginning of the experiment, P concentrations in the outflow remained low, then started to increase and reached a steady state after passing several reactor volumes. This indicates that P was not instantaneously released upon sulfide adsorption but only as lepidocrocite sulfidation progressed. At the end of the experiment, the fraction of P released from the reactor was significantly lower than the fraction of lepidocrocite that had reacted with sulfide(calculated from cumulative sulfide consumption and solid phase characterization). This implies that part of the P has been retained in the solid phase despite the reductive transformation of lepidocrocite. The underlying mechanisms of P retention and the complex relationship between the rates of sulfide consumption and P release will be discussed.</p><p>References</p><p>[1] Jilbert and Slomp, 2013. Geochimica et Cosmochimica Acta 107, 155-169.</p>

Effects of phytase supplementation on growth performance, plasma biochemistry, bone mineralisation and phosphorus utilisation in pre-lay pullets fed various levels of phosphorus

Context Reducing the environmental impact of animal production is becoming a really hot topic, especially with raised concerns over excessive flows of nitrogen and phosphorus (P) to the environment. Aims The present study was conducted to determine the effects of phytase supplementation on growth, plasma biochemistry, bone mineralisation and P utilisation of pre-lay pullets fed varying levels of non-phytate P. Methods A total of 240 Lohmann pullet chicks were randomly allocated to one of six dietary treatments with eight replicate cages (5 birds per cage) per treatment. Six treatments included three phytase-free diets and three diets supplemented with 1000 U/kg phytase; the non-phytate P levels were 2.75–2.50–2.25, 3.75–3.50–3.25 and 4.75–4.50–4.25 g/kg in the former, and 1.75–1.50–1.25, 2.75–2.50–2.25 and 3.75–3.50–3.25 g/kg in the latter, for the age of 0–4, 4–8 and 8–16 weeks respectively. Key results No significant differences were found for growth performance, plasma biochemistry (calcium, P, alkaline phosphatase and albumin) and bone mineralisation among dietary treatments, but P retention (%) was different (P < 0.001). Analysis of planned contrasts showed that phytase supplementation increased phytate P retention (P < 0.001), and improving the utilisation of phytate P tended most efficiently under low P conditions. Total P retention rate was reduced slightly by phytase supplementation (P < 0.05). Conclusions The results indicated that dietary non-phytate P level could possibly be reduced to 1.75, 1.50 and 1.25 g/kg for 0–4, 4–8 and 8–16 weeks of age respectively after phytase supplementation, without compromising pullet growth and performance during the pre-laying period. Implications The results of this study will contribute to decreasing P excretion by poultry and reducing the potential environmental impact with land application of manure.

PSX-38 Late-Breaking Abstract: Sequential feeding with diets varying differ in amino acid content on nutrient balance in growing-finishing pigs

This study evaluated the effect of conventional and sequential feeding programs with diets varying in amino acid content over the day on nutrient balance for growing-finishing pig. Sixty-eight barrows with an average initial BW of 25.0±2.04 were housed in a single pen with five automatic intelligent precision feeders (AIPF; University of Lleida, Lleida, Spain). Pigs were distributed in four feeding programs: 1) conventional feeding (CONV) in which pigs received 100% of SID AA recommendations for the entire day; 2) sequential feeding (SEQ80-120) providing 80% SID AA recommendations from 0000 to 1159h and 120% from 1200 to 2359h; 3) sequential feeding (SEQ70-130) providing 70% SID AA recommendations from 0000 to 1159h and 130% from 1200 to 2359h; and 4) sequential feeding (SEQ60-140) providing 60% SID AA recommendations from 0000 to 1159h and 140% from 1200 to 2359h. Body lean mass and mineral body content were obtained by DXA analysis and were converted to body protein and P content. Three contrasts were constructed to evaluate the effects between CONV and sequential treatments. In phase 1 (0–28d), pigs fed SEQ70-130 presented higher crude protein intake, N retention, N excretion, P intake and P retention (P < 0.05) compared to CONV fed pigs. SEQ 60–140 fed pigs presented higher P retention and P retention efficiency (P < 0.05) compared to CONV fed pigs. In phase 2 (29–54d), no statistical difference for any evaluated variable was verified (P > 0.05). In phase 3 (55–82d), SEQ70-130 fed pigs showed higher N excretion and lower N retention efficiency and lysine efficiency (P < 0.05) when compared to CONV fed pigs. In the entire experimental period (0–82d), there were no significant differences between treatments. According to our results, sequential feeding program improves nutrient balance of pigs at the beginning of the growth period.