Water-soluble Phosphorus Research Articles

Amendment and Soil Type Controls Water-Soluble Phosphorus Recovery from Manure

ABSTRACT A laboratory incubation study was conducted for 35 days to determine the water-soluble phosphorus (WSP) recovery from manure treated soils as influenced by four amendments, spent lime, gypsum, leonardite, and alum. For soil with pH 8.1, WSP of control (soil+manure) increased from 40.1 to 61.8 mg kg−1 on 35 d, application of alum, leonardite, spent line, and gypsum reduced the WSP to 0.15 mg kg−1 (99%), 13.3 mg kg−1 (78%), 34.1 mg kg−1 (45%), and 39.8 mg kg−1 (36%), respectively. Soil with pH 6.7, control had initial WSP of 40.9 mg kg−1 and increased to 80.3 mg kg−1 on 35 d, spent lime, alum, gypsum, and leonardite reduced WSP to 23.6 mg kg−1 (71%), 27.4 mg kg−1 (66), 33.5 mg kg−1 (58%), and 61.1 mg kg−1 (24%), respectively. Alum worked for both soils but the performance of other amendments depends on soil pH and concentration of exchangeable calcium and aluminum.

A higher water-soluble phosphorus supplement in pig diet improves the whole system phosphorus use efficiency

Low phosphorus use efficiency in livestock production has contributed greatly to the unsustainable depletion of phosphorus rock reserves, and to subsequent impacts on the environment. In this study, we compared the effects of two contrasting water-soluble phosphorus supplements on phosphorus use efficiencies through the ‘rock mining – feed – pig – crop’ system, as this whole system analysis has not been explored in previous studies. Weaned piglets were individually fed one of eight different diets that were formulated using two water-soluble phosphorus supplements, a high water soluble (HWS) and a low water soluble (LWS) supplement, at different levels of inclusion in the diet, and production indicators were measured. The total phosphorus content and different phosphorus fractions were measured in the resulting manure, and in the soil following manure application. At the whole system level, the diet supplemented with 0.20%HWS increased average daily gain and apparent total tract digestibility of feed phosphorus by 21.9% and 21.7%, and reduced manure total phosphorus and water soluble inorganic phosphorus by 37.7% and 43.9%, compared with the 0.20%LWS amended diet. The 0.10%HWS supplement increased phosphorus use efficiency of the whole system by 18.1%, compared to 0.20%LWS supplement. These results suggest that a shift of pig feed supplementation from lower to higher water-soluble supplements could be an effective strategy for sustainable phosphorus use through the whole pig production system, and provides new insights for sustainable livestock production in countries with severe challenges from phosphorus shortages and pollution.

ADSORPTION-DESORPTION OF TRACE ELEMENTS IN SEDIMENTS OF THE MAIPO RIVER BASIN

We studied the adsorption-desorption of Cu, Mn, Pb and Zn in Maipo river basin, one of the most perturbed rivers in Chile, and thus determined its tolerance to the addition of these metals into the sediments and the possibility of transferring the metals from the sediments to the water column. Sediments were sampled from six sites from the river basin and characterized by their pH, electrical conductivity, organic carbon, total organic carbon, water soluble phosphorus and texture. Batch sorption and kinetics experiments were conducted to obtain the retained amounts onto the sediment samples. The initial concentration of trace elements in the sediment was quantified by AAS. The metals were present in most of the sites. Sorption parameters such as Kd and Koc were determined. Metals were adsorbed in the sediment, with Mn showing the lowest affinity, Kd and Koc values support these results. Desorption less than 1% were observed for Cu, while Pb and Zn ranged from 0.6% to 6.8% and those for Mn ranged from 0% to 17.6% across sites. The tolerance of the Maipo River to metal adsorption in sediments was as follows: Pb˃ Cu˃ Zn ˃Mn. Desorption analysis showed that both Zn and Mn could be transferred from the sediment to the water column. The strongest correlation occurs between the pH and Kd-Pb, indicating that at higher pH values, the Pb adsorption was unfavorable, while the correlation was moderate for Cu, Mn and Zn. On the other hand, there are positive correlations between pairs of metals such as Mn-Cu, Zn-Cu, and Zn-Mn, indicating the competition of these metals for the adsorbent sites. The high concentration of Mn found in the sediment and the possibility of being transferred to the water column, due to its easy of desorption, suggest concern due to its potential risk to aquatic biota.

Optimization of solid phosphate sludge composting by integration of horticultural waste

Phosphate sludge (PS) is a by-product of phosphate extraction industry and yet, still contain phosphorus bound to calcium what makes it unavailable. Here, we characterized phosphorus fractions in phosphate sludge and their evolution with other plant nutrients during 60 days aerobic composting with tomato plant residues. Two samplings at initial and final stage (5 and 60 days) were performed and analyzed for water-soluble phosphorus (P) fractioning (WSP), P associated with aluminum and iron oxides (Fe/Al-P), P associated with organic matter (OM-P), and P associated with calcium (Ca-P) along with water-soluble potassium (K), Ca, and sodium (Na) that were also analyzed. Results showed that at the initial stage of composting (5 days), the concentration intervals of each P fraction were 0.3 to 0.34 g kg−1, 0.66 to 0.68 g kg−1, 0.29 to 0.55 g kg−1, and 93.21 to 94.87 g kg−1, respectively, for WSP, Fe/Al-P, OM-P, and Ca-P. After 60 days, results revealed an increase in each fraction as follows: 1.36 to 1.40 g kg−1; 3.11 to 3.29 g kg−1; 2.04 to 2.44 g kg−1; and 91.49 to 94.04 g kg−1, respectively, for WSP, Fe/Al-P, OM-P, and Ca-P. Extractable K, Ca, and Na increased whereas total organic carbon decreased after composting. The dominant fraction Ca-P has decreased during composting period and transformed into WSP, Fe/Al-P, OM-P fractions. The slow release in available forms of plant nutrients is a valuable attribute of a mature organic amendment. This confirms that composting could be a promising approach for application of PS and P recovery to arable soils.

High uptake and inward diffusion of iron fortificant in ultrasonicated milled rice

Nutritional iron content in milled rice is generally lost as a result of milling due to removal of aleurone layer. Iron fortification in milled rice is recommended to regain the lost nutrients and address the malnutrition issues. This work investigates the uptake of iron and its diffusion into the kernel on ultrasonic-treated milled rice. Rice samples were subjected to ultrasonic waves resulting in the formation of microporous surfaces and the creation of fissures in the milled rice. Sonication followed by soaking in aqueous iron solution resulted in the uptake of 321 ± 13.43 mg of iron per kg of rice, a 28-fold increase compared to the endogenous iron content of milled rice with retention of 82.9% upon washing and cooking. Cross-section mapping (μ-XRF) of the concentration of the fortificant into the uncooked grains showed inward diffusion at different rates reaching into the kernel core. Results also show that sonication decreased the amount of water-soluble phosphorus in rice suggesting the removal of potentially anti-nutrient phytic acid. Textural analysis of ultrasonic-treated iron-fortified rice premix revealed favorable properties that can be advantageous for its consumer acceptability.

Genomic Predictive Ability for Foliar Nutritive Traits in Perennial Ryegrass.

Forage nutritive value impacts animal nutrition, which underpins livestock productivity, reproduction and health. Genetic improvement for nutritive traits in perennial ryegrass has been limited, as they are typically expensive and time-consuming to measure through conventional methods. Genomic selection is appropriate for such complex and expensive traits, enabling cost-effective prediction of breeding values using genome-wide markers. The aims of the present study were to assess the potential of genomic selection for a range of nutritive traits in a multi-population training set, and to quantify contributions of family, location and family-by-location variance components to trait variation and heritability for nutritive traits. The training set consisted of a total of 517 half-sibling (half-sib) families, from five advanced breeding populations, evaluated in two distinct New Zealand grazing environments. Autumn-harvested samples were analyzed for 18 nutritive traits and maternal parents of the half-sib families were genotyped using genotyping-by-sequencing. Significant (P < 0.05) family variance was detected for all nutritive traits and genomic heritability (h2g) was moderate to high (0.20 to 0.74). Family-by-location interactions were significant and particularly large for water soluble carbohydrate (WSC), crude fat, phosphorus (P) and crude protein. GBLUP, KGD-GBLUP and BayesCπ genomic prediction models displayed similar predictive ability, estimated by 10-fold cross validation, for all nutritive traits with values ranging from r = 0.16 to 0.45 using phenotypes from across two locations. High predictive ability was observed for the mineral traits sulfur (0.44), sodium (0.45) and magnesium (0.45) and the lowest values were observed for P (0.16), digestibility (0.22) and high molecular weight WSC (0.23). Predictive ability estimates for most nutritive traits were retained when marker number was reduced from one million to as few as 50,000. The moderate to high predictive abilities observed suggests implementation of genomic selection is feasible for most of the nutritive traits examined.

Chemical behavior of fluorine and phosphorus in chemical looping gasification using phosphogypsum as an oxygen carrier

In China, the amount of phosphogypsum (PG) has exceeded 250 million tons with more than 55 million tons of growth rates each year. As the micro constituent, fluorine and phosphorus restrict the resourceful disposal of PG. This paper focused on chemical looping gasification (CLG) which used PG as an oxygen carrier, systematically investigated the gasification performance and chemical behavior of fluorine and phosphorus contained in PG during CLG process. Main conclusions are as follows. The main pollutant of chemical looping gasification process was HF, which was transformed from NaF. Phosphorus transformed from water-soluble phosphorus (Ca(H2PO4)2, Ca(HPO4)) into insoluble Ca3(PO4)2.20 reducing-oxidizing cycles were investigated, and a less and less fluorine content in oxygen carrier was found because its phase transformation from solid NaF to gaseous HF, and the phosphorus content in oxygen carrier changed slightly under the current conditions. The Ca3(PO4)2 particle layers existed in both the middle of the reduced solid particles and the middle of the cycled oxygen carrier particles, confirmed to actually act as a glue between the particles. Furthermore, transformation routes of fluorine and phosphorus during the CLG process were discussed and the generation of syngas in CLG process needed to be purified.

Atmospheric deposition of phosphorus to the Northern Indian Ocean

Air-sea deposition of phosphorus is an important external source of this macronutrient for ocean primary productivity. Although global budgets have shown that atmospheric input of phosphorus is comparable to its riverine supply, studies on regional scale are rather limited. The present article summarizes sources and atmospheric pathway of phosphorus to the ocean surface as a case study of the Northern Indian Ocean. Water-soluble aerosol phosphorus (P Inorg ) concentrations are significantly high over the Bay of Bengal (BoB) compared to those over the Arabian Sea (ARS). Relative increase in the supply of aerosol-P over BoB is attributed to acid-processing of mineral dust during long-range atmospheric transport in addition to its supply from anthropogenic sources. Our estimate of P-deposition to the Northern Indian Ocean (~1.2 Gmol-P year -1 ) is comparable to its atmospheric deposition in other oceanic regions such as the North Atlantic and is also consistent with the model-based projections for the Northern Indian Ocean. These results highlight the importance of atmospheric source in influencing the biogeochemical cycle of phosphorus in the Northern Indian Ocean.

Effects of Soil Conditioners on Absorption of phosphorus by waxy corn and Phosphorus Transformation in High Phosphorus Soils

In this experiment, the effects of different types of conditioners and their application on the absorption and transformation of phosphorus in high phosphorus soils in facilities were investigated to improve the environmental problems of protected farmland caused by phosphorus accumulation. Waxy corn was used as a test crop, and five conditioners such as humic acid, biochar, bentonite, alum, and dephosphorized gypsum were used as test materials for potting experiments. The experiment set 10 treatments, namely T1(Blank control), T2(Humic acid), T3(Biochar), T4(Bentonite), T5(Alum), T6 (Dephosphorized gypsum), T7(Biochar-bentonite-alum), T8(Humic acid-biochar-alum),T9(Humic acidbiochar- bentonite-alum),T10(Humic acid-bentonite-biochar-alum-dephosphorized gypsum). Based on the analysis of the results of the three crops, except that the first crop was not significant, the biomass and phosphorus absorption of waxy corn of T2 was the highest in the second crop, and T10 was the most effective treatment in the third crop. The soil available phosphorus content of T8 was the lowest in the second crop and that of T10 was the lowest in the third crop, which were 12.01% and 12.75% lower than the control. The soil water-soluble phosphorus content of T4 was the lowest in the second crop, which was 41.84% lower than the control, and that of T8 was the lowest in the third crop, which was 26.62% lower than the control. According to the results of the three crops, the ratio of the total phosphorus content of the inorganic phosphorus in the third crop of each treatment was increasing compared with the first crop. The soil phosphorus was transformed from organic phosphorus to inorganic phosphorus. The ratio of total phosphorus content of organic phosphorus of T6, T9, T10 was larger than other treatments, which slowed down the conversion of phosphorus to available form. The ratio of Ca8-P in the inorganic phosphorus was the highest, reaching about 50% to 60%. From the results and analysis, T2 and T10 were beneficial to the absorption of soil phosphorus by waxy corn, T8 and T10 were beneficial to slow down the conversion of phosphorus to the effective state, reduce the potential risk of phosphorus environment, improve the phosphorus accumulation environmental issues in greenhouse farmland.

Water-soluble phosphorus contributes significantly to shaping the community structure of rhizospheric bacteria in rocky desertification areas

Microorganisms play important roles in soil improvement. Therefore, clarifying the contribution of environmental factors in shaping the microbial community structure is beneficial to improve soil fertility in karst rocky desertification areas. Here, the bacterial community structures of eight rhizospheric soil samples collected from perennial fruit plantations were analysed using an Illumina HiSeq2500 platform. The diversity and abundance of bacteria in rocky desertification areas were significantly lower than those in non-rocky desertification areas, while the bacterial community structure was not significantly different between root surface and non-root surface soils in the same rhizospheric soil samples. Proteobacteria predominated in rocky desertification areas, while Actinobacteria predominated in non-rocky desertification areas. Correlation analysis revealed that water-soluble phosphorus content (r2 = 0.8258), latitude (r2 = 0.7556), altitude (r2 = 0.7501), and the age of fruit trees (r2 = 0.7321) were positively correlated with the bacterial community structure, while longitude, pH, and total phosphorus content did not significantly influence the soil bacterial community structure. As water-soluble phosphorus content is derived from insoluble phosphorus minerals, supplementing phosphorus-solubilising bacteria to soils in rocky desertification areas is a feasible strategy for accelerating the dissolution of insoluble phosphorus minerals and improving agricultural production and environment ecology.

Activated dolomite phosphate rock fertilizers to reduce leaching of phosphorus and trace metals as compared to superphosphate

Use of water-soluble phosphorus (P) fertilizers such as superphosphates (SP) has been increasingly concerned due to the loss of P and trace metals such as cadmium (Cd) into the environment. Activated phosphate rock holds promising as an alternate due to non-destructive and slow release nature. The objective of this study was to assess the leaching potential of P and trace metals from newly developed activated dolomite phosphate rock (HA-DPR and SLS-DPR), as compared to water-soluble fertilizers, including superphosphate (SP), diammonium phosphate (DAP) and original dolomite phosphate rock (DPR). Two representative agricultural soils (Alfisol and Spodosol soil) were sampled at the 0–20 cm depth from two farms for the column leaching experiments. Seven leachings were conducted at day 1, 3, 7, 14, 21, 28, and 56, respectively, and a total of 1050 mL of deionized water (equivalent to half year's rainfall in the Indian River area) was applied for leaching. Leachates were collected from each leaching event and analyzed for water-soluble P and metals. Activated DPR application led to an increase in soil pH by 1.4–1.7 units, whereas SP resulted in a decrease in soil pH by 0.4–1.6 units. P leaching from activated DPR were 33–61 times less than that from SP or DAP. HA-DPR and SLS-DPR treatments reduced cumulative trace metals in leachate by 1.3–12.3 times for the Alfisol soil, and 1.4 to 8.4 times for the Spodosol soil, respectively. These results indicate that activated DPR fertilizers are more environmentally friendly than water-soluble fertilizers.

Effect of Long-Term Use of Tillage, Crop Residue and N Application on Phosphorus Fractions in Soil under Sorghum (Sorghum vulgare) (L.)-castor System (Ricinus Communis) in Rainfed Alfisol Soils

ABSTRACT A long-term field experiment was conducted at Hayathnagar Research Farm (HRF) of ICAR-Central Research Institute of Dryland Agriculture with the objectives to assess the effect of soil management practices viz tillage, residue application and N levels on soil phosphorus fractions, their interrelationships among themselves, impact on soil P availability pool, crop yields and P uptake. The results of the study clearly indicated that the long-term use of tillage, application of residues and N levels had a significant effect on all the P fractions in soils, except that water-soluble phosphorus (WSP) was not significantly influenced by the tillage practices. The Tillage x Residue x Nitrogen (T × R × N) significantly influenced the reductant soluble phosphorus (RSP) and total phosphorus (TP); however, the remaining P fractions were not influenced significantly. Among the combination of soil management treatments, conventional tillage (CT)+ Gliricidia loppings @ 2 tha−1 (GL) + N level @ 90 kg ha−1 (N90) (CTGLN90) gave the highest sorghum grain yield (1432 kg ha−1) and P uptake (14.20 kg P ha−1). Among the treatment combinations, the order of superiority of treatments in terms of castor yield and P uptake was: CT+ sorghum stover @ 2t ha−1 (SS) + N90 (CTSSN90) (1788 kg ha−1, 11.94 kg P ha−1) > Minimum Tillage (MT) + sorghum stove @2 t ha−1 (SS) + N level @ 90 kg ha−1 (N90) (MTSSN90) (1761 kg ha−1, 14.24 kg P ha−1), respectively. Significant coefficients of multiple determination obtained from regression equations developed between sorghum crop yield and P fractions (R2 = 0.726, p = .05) and sorghum P uptake and P fractions (R2 = 0.620, p = .05) highlighted the importance of these fractions in influencing the crop yield and P uptake. Similarly, castor yield (R2 = 0.748, p = .05) and P uptake (R2 = 0.783) were significantly influenced by the P fractions. The results of the present study will be useful in understanding the effect of soil management practices on the status of P fractions and their contribution toward P uptake and crop yields.

Hematite enhances the immobilization of copper, cadmium and phosphorus in soil amended with hydroxyapatite under flooded conditions

Hydroxyapatite (HA) is often applied as chemical amendment in soils contaminated with trace metals such as copper (Cu) and cadmium (Cd). Large amounts of iron oxides in red soil may interacts with phosphate released from HA and influence trace metal immobilization of HA. Here we simulated a red paddy soil with 1–5% wt iron oxides by adding hematite and evaluated the Cu and Cd availability in soil amended with HA under flooded conditions. Changes in phosphorus and iron oxide fractions were also evaluated after a 42-day flooding incubation experiment. Results showed that the addition of HA-only and hematite-only decreased soil redox potential and increased pore water pH compared to the control. HA combined with hematite could effectively decrease phosphate, Cu and Cd in soil pore water compared to HA-only. Additionally, HA combined with hematite could also increase soil pH and decrease soil CaCl2-extractable Cu and Cd. In particular, HA combined with 5% hematite was most effective in reducing soil exchangeable fractions of Cu and Cd by 53.7% and 65.6% compared to the control, respectively. The addition of HA-only increased water-soluble phosphorus, NaHCO3-extractable inorganic phosphorus, NaOH-extractable inorganic phosphorus, and HCl-extractable phosphorus. Conversely, HA combined with hematite treatments decreased NaHCO3-extractable inorganic phosphorus by 11.3–43.0% compared to HA-only. Vivianite and metal–phosphate precipitates were not observed using the Visual MINTEQ model, X-ray diffraction, and chemical analysis. The addition of hematite with or without HA increased free and crystal iron oxide fractions, while it substantially enhanced amorphous iron oxides in the soil. Thus, this study indicates that soil with high hematite content could enhance Cu and Cd immobilization while decreasing phosphorus availability in the red paddy soil amended with HA under the flooded conditions.

Alkaline phosphatase-harboring bacterial community and multiple enzyme activity contribute to phosphorus transformation during vegetable waste and chicken manure composting.

The objective of this study was to evaluate changes in phosphorus fractions during vegetable waste and chicken manure composting. High throughput sequencing, quantitative PCR, and multiple analysis methods were applied to investigate interconnections among phosphorus fractions, enzyme activity, and phoD-harboring bacterial community composition. We found the highest composting temperature reached 61°C and phosphorus fractions presented significant differences during a 60-day composting. The content of plant-absorbable phosphorus, including water soluble phosphorus, available phosphorus, and citric acid phosphorus increased by 121%, 87%, and 63%, respectively. Additionally, phoD gene abundance significantly correlated with the activities of nine enzymes. Our findings emphasize that microbial activity plays an important role in phosphorus transformation during composting, and the final composting product could be good biological phosphorus fertilizer. To our knowledge, this is the first report indicating that enzyme activity, community composition and abundance of phoD-harboring bacteria have direct and indirect effects on phosphorus transformation during composting.

Enhancement Effect of Water-Soluble Phosphorus on Agronomic Effectiveness of Phosphate Rocks

ABSTRACTDirect application of phosphate rocks (PRs) with low/medium in reactivity has shown to be low in agronomic effectiveness for cereal crops. Presence of water-soluble P (WSP) in the vicinity of PR can significantly enhance the rooting system at the early stage of plant growth. This, in turn, can enable the plant to utilize the associated PR more effectively than the use of PR alone at planting. This report presents the results of several greenhouse experiments that show the granulated (WSP+PR) products by dry compaction process using different low-reactive PR sources were as effective as WSP fertilizers viz triple superphosphate (TSP) and monoammonium phosphate (MAP). The test plants were maize (30 days) and soybean and upland rice were grown to maturity on acid or neutral soils. Based on the results obtained a P ratio of 50:50 between WSP and PR is recommended for the granulated (WSP+PR) products that can achieve crop yields at the same levels as that with the WSP fertilizers.Abbreviations: phosphate rock, PR; water-soluble P, WSP; dry-matter yield, DMY

Phosphorus Availability and Growth of Benthic Primary Producers in Littoral Lake Sediments: Are Differences Linked to Induced Bank Filtration?

Submerged macrophytes and periphyton are benthic primary producers that play an important role for several ecosystem functions of lakes. Their growth often depends on the availability of phosphorus (P) in sediments and overlying water. This P availability is assumed to potentially be affected by induced bank filtration (IBF), a cost-effective method for drinking water production. In this study, we tested whether littoral sediments sampled at sites with high and low influence of IBF in a temperate eutrophic lake used for bank filtration since more than 100 years affects periphyton and macrophyte growth. Sediments differed in aerobic desorbed water-soluble phosphorus (PH2O) and iron (Fe) content and the growth of macrophytes in sediments with a high impact of IBF was lower compared to sediments with low impact of IBF. We also found that P addition to the nutrient solution increased periphyton growth and that periphyton limited macrophyte growth. While these results point to a potential impact of IBF on P availability in sediments that can cascade to benthic primary producers, we could not prove mechanistic links between high rates of IBF and the lower macrophyte growth. Additional research to assure a sustainable application of this valuable drinking water production method is therefore needed.

Phosphogypsum based gypsum binder

Problem statement. Phosphogypsum-based binding materials without pretreatment have poor physical and mechanical characteristics compared to binders made of natural raw materials. This is due to the high value of their specific surface area, which in turn leads to an increase in water demand. Besides, phosphogypsum contains fluorine and phosphorus compounds adversely affecting the final strength. Therefore, neutralization of these compounds and decreasing water demand of phosphogypsum-based gypsum binder is the priority. Based on the preliminary research, we offered a scientific hypothesis of dry neutralization of fluorine and phosphorus compounds in phosphogypsum by an activated silica/calcium carbonate mixture used in the production of phosphogypsum-based binders. Purpose. The research of the effect of various impurities (lime, calcium carbonate, crushed sand, etc.) on gypsum binder obtained from phosphogypsum as well as the improvement of water resistance and manufacturing processes of phosphogypsum-based gypsum binder (setting time, water-to-gypsum ratio, etc.) that mitigate its disadvantages and extend the scope of application. Conclusion. The research has shown that after adding crushed sand and calcium carbonate as neutralizers of water-soluble phosphorus and fluorine impurities can significantly reduce the amount of water-soluble phosphorus compounds and make water-soluble fluorine impurities disappear completely (Table 6), which makes it possible to use phosphogypsum to produce binders that can be used in civil construction. Moreover, this neutralization method almost doesn’t involve emissions of fluoride compounds during the thermal treatment, and besides, physical and mechanical properties of the neutralized phosphogypsum-based hemihydrate CaSO4∙0,5H2O correspond to GVF−4 Grade.

Water quality modelling of the Mekong River basin: Climate change and socioeconomics drive flow and nutrient flux changes to the Mekong Delta

The Mekong delta is recognised as one of the world's most vulnerable mega-deltas, being subject to a range of environmental pressures including sea level rise, increasing population, and changes in flows and nutrients from its upland catchment. With changing climate and socioeconomics there is a need to assess how the Mekong catchment will be affected in terms of the delivery of water and nutrients into the delta system. Here we apply the Integrated Catchment model (INCA) to the whole Mekong River Basin to simulate flow and water quality, including nitrate, ammonia, total phosphorus and soluble reactive phosphorus. The impacts of climate change on all these variables have been assessed across 24 river reaches ranging from the Himalayas down to the delta in Vietnam. We used the UK Met Office PRECIS regionally coupled climate model to downscale precipitation and temperature to the Mekong catchment. This was accomplished using the Global Circulation Model GFDL-CM to provide the boundary conditions under two carbon control strategies, namely representative concentration pathways (RCP) 4.5 and a RCP 8.5 scenario. The RCP 4.5 scenario represents the carbon strategy required to meet the Paris Accord, which aims to limit peak global temperatures to below a 2 °C rise whilst seeking to pursue options that limit temperature rise to 1.5 °C. The RCP 8.5 scenario is associated with a larger 3–4 °C rise. In addition, we also constructed a range of socio-economic scenarios to investigate the potential impacts of changing population, atmospheric pollution, economic growth and land use change up to the 2050s. Results of INCA simulations indicate increases in mean flows of up to 24%, with flood flows in the monsoon period increasing by up to 27%, but with increasing periods of drought up to 2050. A shift in the timing of the monsoon is also simulated, with a 4 week advance in the onset of monsoon flows on average. Decreases in nitrogen and phosphorus concentrations occur primarily due to flow dilution, but fluxes of these nutrients also increase by 5%, which reflects the changing flow, land use change and population changes.

Effect of Different Levels of Water Soluble Phosphorus in Complex Fertilizers on Crop Productivity and Soil Health

Field experiments were undertaken on sandy soils with three cropping systems at Giridih, Jharkhand, India for two years during 2012-2014. The experiments were executed in split plot design by assigning water soluble phosphorus (WSP) fertilizers in main-plot and recommended dose of phosphorus (RDP) in sub-plot with three replications. The maximum economical yield of rice (4705 kg/ha), baby corn (842 kg/ha) and Chickpea (920 kg/ha) were recorded with the application of 30% WSP. The maximum economical yield of successive crops - wheat (3185 kg/ha), mustard (1720 kg/ha) and groundnut (1578 kg/ha) were recorded with the application of 30% WSP and 100% RDP treatment. Almost similar trends were noticed in terms of by-product yield, nutrient uptake and residual soil fertility status. All the levels of WSP (30% - 89%) in complex fertilizers were found to be equally effective for grain yield, straw yield, nutrient uptake, and residual soil fertility.

Phosphorus speciation and bioavailability of sewage sludge derived biochar amended with CaO

In this study, biochar samples were prepared from the co-pyrolysis of sewage sludge (SS) and CaO to explore the transformation of P speciation in sample. The potential of these biochar as a fertilizer to promote the growth of the plant was also evaluated. The result indicated that CaO addition can greatly facilitate the conversion of non-apatite inorganic phosphorus (NAIP) to apatite inorganic phosphorus (AP, mainly Ca3(PO4)2 and Ca3Mg3(PO4)4). The addition of 10% CaO in feedstock is sufficient to convert SS inherent P into more bioavailable AP. Under such a dosage, AP content in biochar increased by 21.2–33.6% in contrast to CaO free sample at pyrolysis temperature of 500–800 °C, and water-soluble phosphorus (WSP) content decreased to less than 1% of TP. The addition of CaO can also apparently reduce Zn, Mn leaching from biochar. Additionally, hydroponics assay showed that CaO amended SS biochar can promote the growth of rice seedling. The results of this study indicate that preparing CaO amended SS biochar is a technically feasible strategy to utilize P resource in SS.