Bioavailable Phosphorus Content Research Articles

Effect of phytase corn addition on ethanol yield and distillers' dried grains with soluble profile in corn dry‐grind process

AbstractBackground and ObjectivesPhytase as a feed additive improves the bioavailable phosphorus content of the poultry diet, thereby decreasing dependence on externally added phosphorus. The objective of this study was to determine the effect of adding phytase corn on ethanol yield and distillers' dried grains with soluble (DDGS) composition during a corn dry‐grind process.FindingsPhytase corn at 2.5%, 5%, 7.5%, and 10% w/w of fermentable corn was added during the dry‐grind process. Upon fermentation, the ethanol yield was observed to be in the range of 17.9%–18.9% v/v compared to control (17.7% v/v), representing an 1%–6.5% increase in ethanol yield. Relative to the corn that was introduced at the beginning of the fermentation, the DDGS obtained from the control corn or phytase corn addition all showed a threefold increase in oil, protein, and neutral detergent fiber content. However, the phytic acid content of the DDGS was reduced from 0.45% w/w (control) to 0.13% w/w (phytase treatments).ConclusionAdding phytase corn in a dry‐grind process improves the ethanol yield and reduces phytate‐bound phosphorus content.Significance and NoveltyPhytase corn addition will improve the ethanol yield, DDGS nutritional quality in a corn dry‐grind process, and reduce dependence on phosphorus supplementation.

Evaluation of acid mine drainage sludge as soil substitute for the reclamation of mine solid wastes.

The reclamation of mine waste deposits is often hindered by the scarcity of natural topsoil. Acid mine drainage sludge (AMDS), as a mass-produced waste in metalliferous mines, is a potential topsoil substitute but had not been validated. In this study, a pot experiment with three plant species was conducted to evaluate the capacity of AMDS to support plant growth, buffer acidification, and immobilize heavy metal(loid)s when reclaiming mine waste rocks. Chemical fertilizer and compost chicken manure were applied to AMDS at different rates to explore their effects on plant growth and the physicochemical properties of AMDS. Results showed that all the plants could survive in AMDS even without fertilization. The contents of heavy metal(loid)s in rhizosphere remained almost unchanged over the experimental period, indicating low leachability of revegetated AMDS. Fertilizers enhanced macronutrients and soil enzyme activities, leading to significant increases in plant biomass. However, owing to manure composting and low richness and diversity of the bacterial community in AMDS, the NH4+-N and bioavailable phosphorus contents were extremely low. Bermuda grass was a suitable pioneer species for reclamation for its better adaptability to nutrient deficiency and heavy metal(loid) stress. Overall, AMDS is a viable soil substitute for mine reclamation due to its capability to support plant growth and environmental safety.

Impact of river dams on phosphorus migration: a case of the Pubugou Reservoir on the Dadu River in China

Reservoirs in agricultural catchments retain large proportions of inflowing phosphorus (P). However, the effects of reservoirs on the P cycle and related biogeochemical processes remain unclear. Therefore, this study investigated the degree to which a typical river-transition-reservoir in Southwest China retains both inflowing particulate phosphorus (PP) and dissolved total phosphorus (DTP) and various forms of P in sediments over different water seasons [normal-water season (NWS), low-water season (LWS), and high-water season (HWS)]. The proportions of inflowing PP and DTP retained were 37% and 27%, respectively. This result could be attributed to the absorption of DTP by the large load of intercepted sediment in the dam and the interception of PP itself. The rank of water seasons in terms of the proportion and load of inflowing TP retained was LWS (79%, 336 t P yr−1) > NWS (21%, 43 t P yr−1) > HWS (4%, 27 t P yr−1), which might be due to the high P concentration 0.78 mg L−1 and long hydraulic retention time (HRT) 780 d during the LWS. In the long-term, there was a high rate of retention of bioavailable phosphorus (BAP) in sediments (63%). This result could be attributed to the combined effect of fine sediment particles and organic matter (OM). In addition, HRT (R2 = 0.89, p < 0.05) affected the retention of P more significantly than P concentration (R2 = 0.56, p < 0.05). Dam interception during the LWS resulted in high BAP contents (280 mg kg−1) in sediments, high P concentrations (0.78 mg L−1), and weak hydrodynamics (HRT: 780 d) in overlying water. Therefore, further regulatory measures are urgently demanded during the LWS to prevent reservoir algal blooms.

Improvement of nitrogen and phosphorus availability by Pseudoalteromonas sp. during salt-washing in saline-alkali soil

In saline-alkali soils, the inactivation of phosphorus and loss of nitrogen resulting in soil infertility could be intensified by salt, which simultaneously leads to pollution of water sphere. However, there is no complete solution for this challenge due to the weak nutrients biological turnover caused by salt dynamic accumulation. In this study, halophilic marine bacteria strains with carriers were screened to decrease the leaching of nitrogen and phosphorus inactivation in saline-alkali soil during salt-washing. Results showed the combination of Pseudoalteromonas sp. CF8-6 and corn cob significantly increased not only soil available phosphorus by 37.03%, but also the soil bioavailable phosphorus content. Moreover, the concentration of TN, NO3−, TP and PO43− in salt washing eluents reduced by corn cob colonized with CF8-6 significantly. It was also found that the abundance of nitrogen-fixing bacteria (such as Azotobacter), and abundance of Proteobacteria and Actinobacteria in soil were all increased by this combination, which were corresponding for the turnover of nitrogen and phosphorus. We demonstrated that the combination of CF8-6 and corn cob has promising potential in improvement of bioavailability of soil nitrogen and phosphorus during the salt-washing process in saline-alkali soil.

Effect of addition of lanthanum-modified bentonite(Phoslock&lt;sup&gt;&amp;#174;&lt;/sup&gt;) in sediments on growth of &lt;i&gt;Hydrilla verticillata&lt;/i&gt; under different water nutrient concentration

轮叶黑藻（Hydrilla verticillata）是我国浅水湖泊常见的沉水植物，经常用于湖泊生态修复工程.然而在生态修复中后期，轮叶黑藻又往往会过度繁殖，影响其他湖泊功能的发挥.镧改性膨润土（锁磷剂）可以有效地降低沉积物中生物可利用磷含量，近年来被用于控制湖泊沉积物磷释放，其对轮叶黑藻生长和形态的影响还有待阐明.本研究在2种不同上覆水营养盐浓度条件下，设置添加和不添加锁磷剂2种处理，探究沉积物添加锁磷剂对轮叶黑藻生长及形态特征的影响.结果表明：1）沉积物添加锁磷剂之后，铁锰结合态磷、有机磷、铝结合态磷等生物可利用磷浓度显著降低，而生物不可用磷，如钙结合态磷浓度显著升高；2）沉积物添加锁磷剂显著降低了轮叶黑藻的生物量和生长率.添加锁磷剂的处理组植物的株高、地上部分生物量均明显低于无锁磷剂组；相反，添加锁磷剂显著增加了植物的根长和地下部分生物量，进而提高了植物的根冠比；3）锁磷剂对轮叶黑藻生长的影响程度与水体营养盐浓度有关，在低营养盐浓度水体中锁磷剂对植物生长和形态特征的影响更为显著.本研究表明，锁磷剂的添加能降低沉积物中生物可利用磷浓度，抑制轮叶黑藻的生长，同时这种影响程度与在水体营养盐浓度有关.;Hydrilla verticillata is a common submerged plant in shallow lakes in China, and is often used as a pioneer species in lake ecological restoration projects. However, the Hydrilla verticillata tends to overgrowth, forming a canopy which affects other functions of lakes. Lanthanum-modified bentonite (Phoslock^®) can effectively reduce the bioavailable phosphorus content in sediments. In recent years, it has been used to control phosphorus release from lake sediments. Its impact on the growth and morphology of Hydrilla verticillata remains to be clarified. In this study, two treatments with and without Phoslock^® in the sediments were set up to investigate the effects of Phoslock^® on the growth and morphological characteristics of Hydrilla verticillata under two different water nutrient concentrations. The results show that:1) After adding Phoslock^® to the sediments, the bioavailable phosphorus concentration, such as Fe/Mn combined phosphorus (BD-P), organic phosphorus (Org-P), Aluminum-bound phosphorus (Al-P), is significantly reduced, while the non-bioavailable phosphorus concentration, such as Calcium-bound phosphorus (Ca-P), is significantly increased. 2) The addition of Phoslock^® in the sediments significantly reduced the biomass and growth rate of the Hydrilla verticillata. The plant height and aboveground biomass of Phoslock^® group were significantly lower than those without Phoslock^®; on the contrary, the addition of Phoslock^® significantly increased the root length of the plant and the underground biomass, and increased the plant's root-shoot ratio. 3) The effect of Phoslock^® on the growth of Hydrilla verticillata is related to the concentration of nutrients in the water, and the effect of Phoslock^® on plant growth and morphological characteristics is more significant in low-nutrient water. Overall, this study shows that the addition of Phoslock^® can effectively reduce the concentration of bioavailable phosphorus in sediments and inhibit the growth of Hydrilla verticillata, and this effect is more significant when the concentration of nutrients in the water is reduced.

Dynamics of phosphorus fractions and potential bioavailability along soil profiles from seasonal-flooding wetlands in a Chinese estuary.

Soil phosphorus fractions in wetland ecosystems have received increasing attention due to its high eutrophication risks. Soil samples were collected to 40 cm depth in three sampling seasons to investigate the seasonal dynamics of organic and inorganic phosphorus fractions, bioavailability, and relationship between those and soil properties in a seasonal-flooding wetland in the Yellow River Estuary. The results showed that inorganic phosphorus (IP) and organic phosphorus (OP) contents exhibited much higher levels in the top 10cm soils, and declined along soil profiles in spring. IP kept constant along soil profiles in fall, while OP decreased in summer and fall. They were greatly affected by water content (WC), pH, Cl-/SO42-, soil organic matter (SOM), and electrical conductivity (EC). Middle labile organic phosphorus (MLOP) and non-labile organic phosphorus (NLOP) accounted for higher percentages of total OP in summer and fall respectively than labile organic phosphorus (LOP) in spring. MLOP and NLOP levels showed a decrease along soil profiles in spring and in spring/fall, respectively, while NLOP significantly increased with depth in summer. Ca-P was the dominant IP fraction in all soils in three sampling seasons, declined with depth in spring/fall and increased in summer. Comparatively, soluble/loosely-P(S/L-P) generally decreased with depth along soil profiles in three sampling seasons. And residual P (Res-P) kept little change with depth in spring. Fe/Al-P levels decreased firstly and then increased with depth in spring and summer. Available phosphorus and potential bioavailable phosphorus contents decreased with depth in spring and summer not in fall, and had a strong significant positive correlation with WC and SOM. Alkaline phosphatase not acid phosphatase was the key factor influencing soil MLOP levels. Generally, the fractions and bioavailability of phosphorus as well as phosphatase in this region were affected by soil depth, sampling seasons, and soil properties (e.g., WC, pH, Cl-/SO42-, SOM, and EC).

Changes of soil bioavailable phosphorus content in the long-term field fertilizing experiment

The aim of this study is to describe the changes of bioavailable phosphorus content in soil in long-term 18 years field experiments with different fertilizing systems. The field experiments are located at three sites with different soil and climatic conditions in the Czech Republic (Červený Újezd, Humpolec and Prague-Suchdol). Same fertilizing systems and crop rotation (potatoes (maize) – winter wheat – spring barley) are realized at each site with following fertilizing treatments: (1) unfertilized treatment (control), (2) farmyard manure (FYM), (3) and (4) sewage sludge (SS 1 and SS 3), (5) mineral nitrogen (N), (6) mineral nitrogen with straw (N + straw) and (7) mineral nitrogen with phosphorus and potassium (NPK). The long-term fertilizing effect on available P content changes in soil was observed. Bioavailable phosphorus content in soil increased in treatments with organic fertilization after 18 year experiment at all sites. The treatments SS 3 had the highest increase at all sites. The highest bioavailable P content increase compared to control (258 mg/kg) was determined at site Červený Újezd. On the contrary, available phosphorus content decreased at treatments with mineral fertilization and control treatment among all sites. Bioavailable P content decrease in the treatment NPK was observed, although phosphorus was applied. The lowest differences in available P content among all fertilizing treatments were observed at the location Prague-Suchdol.

Enchytraeid Community (Annelida, Clitellata, Enchytraeidae) and Its Dependence on Edaphic Conditions in Rice Agroecosystems in Russia

Communities of soil animals (meso- and macrofauna) in rice paddies tend to be fragmented, and have extremely low abundance. Nevertheless, some groups, such as enchytraeids, may become dominant in flooded conditions, as shown in tropical rice agroecosystems. However, the fauna and functional composition of enchytraeids (Annelida, Clitellata, Enchytraeidae) under such conditions have not yet been studied at temperate latitudes. We have investigated enchytraeid communities and the ratio of their functional groups in the main rice-growing regions of Russia: Krasnodar krai, Primorsky krai, and the Republic of Kalmykia. Samples were taken in summer–early autumn of 2016 in four habitat types: flooded rice paddies, drained paddies occupied by upland crops, adjacent bunds, and undisturbed grasslands (control). Generalized linear model analysis showed that the factor habitat type and its interaction with the factor region had a significant effect on the total enchytraeid abundance, with the factor region alone having no such effect. Their abundance was the highest in the control habitats and bunds (mean and standard error for all the regions: 3278 ± 1131 and 3255 ± 762 ind./m2, respectively), being insignificantly lower in the paddies under upland crops (1282 ± 850 ind./m2) and decreasing to a minimum of 415 ± 323 ind./m2 in the flooded paddies. A comparison between the last two habitat types shows that enchytraeids can relatively quickly restore their abundance in the rice paddies after draining. Principal component analysis revealed a positive correlation between the density of enchytraeids belonging to basophilous ecological group and bioavailable phosphorus content. The correlation between the abundance of acidophilous enchytraeids and this parameter was negative. Thus, the abundance ratio of enchytraeid ecological groups could be used as an informative indicator of the concentrations of nutrient elements and depends on physical and chemical characteristics of paddy soils. Despite the low abundance of enchytraeids in these soils, they can be an important component of the detrital food webs during periods of paddy-drainage in intensive rice agroecosystems at temperate latitudes.

Effects of Exogenous Carbon Addition on Equilibrium Phosphate Concentration and Risk of Phosphorus Release from Sediments in the Shiwuli River, Chaohu Lake Basin

Five surface sediment samples were collected every two months from the Shiwuli River along an urban-rural gradient, Chaohu Lake Basin, from July 2017 to May 2018. Sediment phosphorus fractions were investigated, and equilibrium phosphate concentration (EPC0) and its response to exogenous carbon (sodium acetate) addition were explored. Moreover, the risk of phosphorus release from sediment into water column was also evaluated. Results show that the Shiwuli River was seriously polluted by phosphorus. The average values of total phosphorus content in sediments ranged from 915.04 to 1205.31 mg·kg-1, and it decreased slowly along the urban-rural gradient, while the bio-available phosphorus content remained stable. Exogenous carbon addition not only reduced the EPC0 values of sediments (about 29%), but changed the order of EPC0 values among the five sampling sites as well. In general, the ratio of overlying water SRP (soluble reactive phosphorus) concentration to EPC0 value was 66.7%, and phosphorus adsorption-desorption equilibrium saturation EPCsat<-20% accounted for about 60.0%, indicating that the surface sediments in the Shiwuli River were dominated by phosphorus adsorption, namely, keeping the phosphorus "sink" state. The inputs of exogenous carbon addition increased the proportion of EPCsat<-20% from 60.0% to 73.3%, which lowered the risk of phosphorus release from sediments.

Improved utilization of phosphorous from sewage sludge (as Fertilizer) after treatment by Low-Temperature combustion

The utilization of phosphorus from sewage sludge is an important method used to solve the shortage of phosphorus resources in the world. However, high levels of toxic compounds and low phosphorus bioavailability in sewage sludge are the main factors limiting its direct agricultural use. This paper proposes a low-temperature combustion method that can enrich the phosphorus in sludge ash. Low temperature-treated sewage sludge ash (LTSA) at different oxygen concentrations (20%, 60%, 100%) were obtained through a specific experimental device. Then, the species and leaching characteristics of phosphorus in LTSAs were analyzed and compared with pyrolysis sewage sludge char (PSSC) and incinerated sewage sludge ash (ISSA). Results show that low-temperature combustion of sludge increased the total phosphorus content in the bottom ash by 45.6%, and the bioavailable phosphorus content increased 2.9 times. Further, by increasing the concentration of oxygen while carrying out low-temperature combustion of sludge, part of the non-apatite inorganic P was converted to apatite P (AP), resulting in a 46.3% increase in AP in the sludge. Low-temperature combustion can also convert heavy metals (Cd, Cr, Cu, Pb, and Zn) in the sludge from an easily leachable form (acid extractable fraction and reducible fraction) to a stable form (reducible fraction) and decrease the leaching of heavy metals. Leaching of Cr and Cu decreased by 97.56% and 98.52%, respectively.

Efficacy of Phoslock® on the Reduction of Sediment Phosphorus Release in West Lake, Hangzhou, China

Famous as the world cultural heritage, West Lake in Hangzhou city has plenty of soft sediments with high organic matter content. To search the countermeasures for internal phosphorus release reduction from the sediment, the sediment core incubation was conducted to understand the efficacy of Phoslock® on internal phosphorus release in spring, summer and winter, respectively. The results showed that the internal phosphorus release fluxes in winter and spring were relatively low, with averaged values in the entire lake of 0.13 mg·(m2·d)-1 and 0.29 mg·(m2·d)-1, respectively, while the release flux was 3.29 mg·(m2·d)-1 in summer, more than ten times higher than those in spring and winter. It was estimated that 23.7 kg of phosphorus could be released from sediment in the entire lake every day in summer. Spatially, the phosphorus release flux was related to organic matter contents in sediments, but not the phosphorus or bioavailable phosphorus contents in sediments in West Lake. With Phoslock® added at the rate of 630 g·m-2, sediment phosphorus release was successfully controlled, which reduced the phosphorus concentration in the lake water to less than 0.010 mg·L-1. Especially during summer time, the sediment phosphorus release was reduced by 98% after Phoslock® application. The research suggested that Phoslock® is powerful for phosphorus control even for sediments with high organic matter content, which could be considered in ecological restoration of WEst Lake.

Estimation of phosphorus bioavailability from composted organic wastes

Sewage sludge derived from municipal sewage treatment plants is an important source of macronutrients, micronutrients and organic matter. For this reason composting of sewage sludge, along with combustion and co-combustion, is a new management priority in Poland. In this study six composts of different origin and composition were evaluated in terms of their abundance in phosphorus, because it is an essential nutrient for all living organisms. Analyses were conducted on the samples at the initial and at the maturation phase of composting. The bioavailability of phosphorus was estimated on the basis of amounts of the nutrient in isolated fractions using the sequential extraction method. First of all quantitative changes of the total nutrient content and its amounts in separated fractions were dependent on the mixture composition. Irrespective of compost type, 34.5–75.0% of the total amounts of phosphorus were found in hardly available combinations (Fr. III), while available phosphorus forms (Fr. I) accounted for only 6.6–21.6%. As a result of composting together different organic wastes an increase was observed both in the total content and the amounts of this nutrient in separated fractions. This phenomenon was observed particularly in composts with smaller levels of sewage sludge (30–40%), characterised by rapid organic matter decomposition, which was indicated by higher bioavailable amounts of phosphorus. Under such conditions the content of P ranged between 3.68 and 7.4 g kg−1. In comparison to the labile pool of P obtained for matured composts C5 and C6 (65 and 75% of sewage sludge in their composition) amounting to 2.45–3.0 g kg−1 the above values were considerable. Bioavailable phosphorus contents potentially introduced to soil with composts doses calculated at 170 kg total N/ha/yr ranged from 69.8 to 80.2 kg for compost with the lowest share of sewage sludge and from 11.2 to 20.7 kg for compost with the highest share of sewage sludge.

Phosphorus speciation in wetland sediments of Zhujiang (Pearl) River Estuary, China

Phosphorus fractions and adsorption-release characteristics of sediments in the Zhujiang (Pearl) River estuary wetland were investigated. Results showed that the total phosphorus (TP) content in surface sediments ranged from 648.9 mg/kg to 1064.0 mg/kg; inorganic phosphorus (IP) was the major fraction of TP and ranged from 422.5 mg/kg to 643.9 mg/kg. Among the inorganic phosphorus, the main fractions were phosphorus bound to Al and Fe (Fe/Al-P), and calcium-bound phosphorus (Ca-P), accounting for 23%–42% and 21%–67% of IP, respectively. The vertical distribution of TP contents were significantly positive correlated with organic phosphorus (Org-P) and Fe/Al-P contents. The bio-available phosphorus contents in vertical sediments varied from 128.6 mg/kg to 442.9 mg/kg, mainly existed in Fe-Al/P fraction, and increased from the bottom to top sediments. The transport of phosphorus in sediment-water interface was controlled by the soil characteristics. The active Fe and Al content was considered as the main factor that determines adsorption capacity in vegetated marsh wetland. The P buffering capacity of the sediments in vegetated marsh wetland was greater than that in mudflat wetland. The potential risk of eutrophication in the study area is high. Reducing terrestrial phosphorus discharge and preventing the sediment Fe/Al-P release to the interstitial water are the possible solutions to reduce the risk of eutrophication in estuary wetlands, and planting vegetation in estuary wetland can also reduce the release of phosphorus in surface sediment.

The Distribution Characteristics of Soil TP and IP Forms at the Xiangxi River Riparian Zone in the Three Gorges Reservoir

The soil samples along the Xiangxi River bank in the Three Gorges Reservoir were collected at exposed period. The total phosphorus and inorganic phosphorus contents in soil were determined, and their distribution characteristics were analyzed. The results show that the average content of TP is 1.0735gkg-1 (145-175m) and 1.225gkg-1 (175-185m) respectively. The downstream and upstream has the maximum and minimum values respectively. Ca-P and O-P are the major IP forms of Xiangxi River riparian zone. The midstream and upstream (145-175m) has the maximum and minimum content of Al-P and Fe-P respectively, while the downstream (175-185m) has maximum content of Al-P and Fe-P respectively. The downstream (145-185m) has minimum content, while the upstream and midstream has the maximum content of WS-P and O-P respectively. The upstream and downstream (145-185m) has the maximum and minimum content of Ca-P respectively. The bio-available phosphorus content decreased gradually and bio-unavailable phosphorus content increased gradually from downstream to upstream.

Phosphorus Fractionation and Bio-availability in Surface Sediments from the Middle and Lower Reaches of the Yellow River

Abstract Species and bioavailability of phosphorus in surface sediments from the middle and lower reaches of the Yellow River were investigated using the sequential extraction method. Sedimentary inorganic phosphorus were fractioned into four forms and the rank order according to the mean concentration of P-fraction in Yellow river was HCl-P > NaOH-P > BD-P > NH4Cl-P. The linear relationship between the sum of BD-P and NaOH-P and the sum of active Fe and active Al content was observed within the twelve sediments investigated (R2=0.66). Moreover, the bio-available phosphorus (BAP) content was estimated by the sum of NH4Cl-P, BD-P, and NaOH-P, viz. BAP = NH4Cl-P + BD-P + NaOH-P. In Yellow River, the BAP contents were ranging from 0.031 mg/g dw (dry weight) to 0.066 mg/g dw, and average 0.050 mg/g dw for all sediment samples. The relative contributions of BAP to inorganic sedimentary phosphorus (IP) range from 41% to 62% (53% on average).

Distribution of Bioavailable Phosphorus (BAP) in lake sediments of the middle and lower reaches of the Yangtze River

Bioavailable Phosphorus (BAP) in sediments of Lake Taihu (6 sites) , Lake Chaohu (4 sites) and Lake Longgan (3 sites) was analyzed by chemical extraction method. The mean BAP content in north Lake Taihu was 259.5 mg/kg, 114. 6 mg/kg in west of Lake Taihu, 40. 6 mg/kg in the middle of the lake and 50. 7 mg/kg in East Lake Taihu. It was very obvious that BAP contents were higher in the north of the lake and lower in the south. The mean BAP content in the west of Lake Chaohu was 254. 2 mg/kg while was 101. 9 mg/kg in the east of the lake. The content is 67. 8 mg/kg in Lake Longgan. All these data showed the more polluted lakes (lake zones) was with higher BAP contents in the sediments. The BAP contents in the sediment cores decreased exponentially that meant the BAP would transform to non-bioavailable form with sedimentation effect. Because of the higher bioactivity in summer, the BAP was more easily transformed to soluble phosphorus and resulted in lower content in the sediment. There was positive correlation between the BAP contents in sediments and soluble reactive phosphorus ( SRP) and the correlation was better in the lakes/lake zones with lower BAP contents than in the lakes/lake zones with higher contents.

Soil nutrient factors related to salidroside production of Rhodiola sachalinensis distributed in Chang Bai Mountain

Salidroside is the active ingredient in the roots of a Chinese medicine herb, Rhodiola sachalinensis A. Bor. Salidroside content in the Rh. sachalinensis differs greatly in different natural habitats. The effects of soil nutrient factors on the salidroside production in the root of Rh. sachalinensis were for the first time investigated in Chang Bai Mountain, PR China. The results showed that rich organic matter, low pH and high levels of exchangeable nitrogen and total nitrogen in soil were most essential to guarantee the high productivity of salidroside. The salidroside yield reached higher than 0.7% of root dry weight when the soil pH value was about 4.5, the soil organic matter content was higher than 17% or soil exchangeable nitrogen and total nitrogen contents were higher than 34 mg/100 mg and 0.6% of soil dry weight, respectively. However, soil bioavailable phosphorus content higher than 5 ppm and exchangeable potassium content higher than 180 ppm resulted in a low salidroside yield, only about 0.2% dry weight. This investigation will guide the soil management on how to select soil and how to fertilize the soil for the cultivation of Rh. sachalinensis to improve the salidroside productivity.

Estimating runoff phosphorus losses from calcareous soils in the Minnesota River basin.

Bioavailable phosphorus (BAP) in stormwater runoff is a key issue for control of eutrophication in agriculturally impacted watersheds. Laboratory experiments were conducted in soil runoff boxes to determine BAP content in simulated storm runoff in 10 (mostly) calcareous soils from the Minnesota River basin in southern Minnesota. The soluble reactive phosphorus (SRP) portion of the runoff BAP was significantly correlated with soil Mehlich-III P, Olsen P, and water-extractable P (all r2 > 0.90 and p < 0.001). A linear relationship (r2 = 0.88, p < 0.001) also was obtained between SRP in runoff and the phosphorus saturation index based on sorptivity (PSIs) calculated with sorptivity as a measure of the inherent soil P sorption capacity. Runoff levels of BAP estimated with iron oxide-impregnated paper were predicted well by various soil test P methods and the PSI, of the soils, but correlation coefficients between these variables and runoff BAP were generally lower than those for runoff SRP. Using these relationships and critical BAP levels for stream eutrophication, we found corresponding critical levels of soil Mehlich-III P and Olsen P (which should not be exceeded) to be 65 to 85 and 40 to 55 mg kg(-1), respectively.

An Innovative Approach to Estimate Bioavailable Phosphorus in Agricultural Runoff Using Iron Oxide‐Impregnated Paper

AbstractThe transport of bioavailable phosphorus (BAP) in agricultural runoff can accelerate the eutrophication of receiving water bodies. Bioavailable P is comprised of dissolved P (DP) and bioavailable particulate phosphorus (BPP). Although several algal assays and chemical extractions have been proposed to estimate BAP, procedural and theoretical limitations have restricted their widespread use. This study evaluates the use of Fe oxide‐impregnated paper strips (Fe‐oxide strips) to estimate the potential BAP content of runoff from 20 agricultural watersheds in the Southern Plains during 1988 to 1990. In the proposed method, BAP and DP are determined by shaking 50 mL of unfiltered or filtered runoff, respectively, with one Fe‐oxide strip for 16 h. Phosphorus is removed from the strip by 0.1 M H2SO4 and measured, with BPP calculated as the difference between BAP and liP. Growth of Selenastrum capricornutum was related (r2 = 0.63–0.96) to the BPP content of runoff sediment in 2‐ to 29‐d incubations. Bioavailable PP estimated by the proposed strip method and more widely used NaOH extraction, closely followed a 1:1 relationship. Averaged for all runoff events, strip DP was 90 and 75% of DP determined by standard direct methods, for watersheds with and without tillage, respectively. The lower estimates of strip DP may be partially attributed to a greater transport of acid‐hydrolyzable organic and condensed DP in runoff from no‐till compared to tilled watersheds. Acting as a P sink, the strip method may have a stronger theoretical basis than chemical extraction in estimating algal‐available P in agricultural runoff. In addition, the simplicity of the proposed Fe‐oxide strip method will allow BAP estimation with limited resources and may facilitate evaluation of the impact of agricultural runoff on the biological productivity of receiving waters.

Assessing phosphorus bioavailability in agricultural soils and runoff

Bioavailable phosphorus (BAP) transported in agricultural runoff can accelerate surface water eutrophication. Although several algal assays and chemical extractions have been proposed to estimate BAP, procedural and theoretical limitations have restricted widespread BAP measurement. Thus, a routine method was developed to estimate BAP, which uses iron oxide-impregnated paper strips (Fe-oxide strips) as a P-sink for BAP in runoff. In the proposed method BAP is determined by shaking 50 mL of unfiltered runoff with one Fe-oxide strip for 16 h. Phosphorus is removed from the strip by 0.1M H2SO4 and measured. The BAP content of runoff from 20 agricultural watersheds in the Southern Plains was related to the growth of P-starved algae incubated for 29 d with runoff as the sole source of P. Acting as a P sink, Fe-oxide strips may have a stronger theoretical basis than chemical extraction in estimating BAP. The method may also have potential use as an environmental soil P test to indicate soils liable to enrich runoff with sufficient P to accelerate eutrophication. Bioavailable P loss in runoff was lower from no till (438 g ha−1 yr−1) than from conventional till (1288 g ha−1 yr−1). Kinetic and enrichment ratio approaches accurately predicted (r2 of 0.93) BAP transport in runoff during 1988 to 1990. Use of the Fe-oxide strip method will facilitate estimation of BAP transport in runoff and thereby, improve assessment of the resultant impact on the biological productivity of receiving surface waters.