Enhancing nutrient recycling from excreta to meet crop nutrient needs in Sweden - a spatial analysis.

Increased recycling of nutrient-rich organic waste to meet crop nutrient needs is an essential component of a more sustainable food system. However, agricultural specialization continues to pose a significant challenge to balancing crop nutrient needs and the nutrient supply from animal manure and human excreta locally. For Sweden, this study found that recycling all excreta (in 2007) could meet up to 75% of crop nitrogen and 81% of phosphorus needs, but that this would exceed crop potassium needs by 51%. Recycling excreta within municipalities could meet 63% of crop P nutrient needs, but large regional differences and imbalances need to be corrected to avoid over or under fertilizing. Over 50% of the total nitrogen and phosphorus in excreta is contained in just 40% of municipalities, and those have a surplus of excreta nutrients compared to crop needs. Reallocation of surpluses (nationally optimized for phosphorus) towards deficit municipalities, would cost 192 million USD (for 24 079 km of truck travel). This is 3.7 times more than the total NPK fertilizer value being transported. These results indicate that Sweden could reduce its dependence on synthetic fertilizers through investments in excreta recycling, but this would likely require valuing also other recycling benefits.

Boron: Functions and Approaches to Enhance Its Availability in Plants for Sustainable Agriculture.

Boron (B) is an essential trace element required for the physiological functioning of higher plants. B deficiency is considered as a nutritional disorder that adversely affects the metabolism and growth of plants. B is involved in the structural and functional integrity of the cell wall and membranes, ion fluxes (H⁺, K⁺, PO43−, Rb⁺, Ca2+) across the membranes, cell division and elongation, nitrogen and carbohydrate metabolism, sugar transport, cytoskeletal proteins, and plasmalemma-bound enzymes, nucleic acid, indoleacetic acid, polyamines, ascorbic acid, and phenol metabolism and transport. This review critically examines the functions of B in plants, deficiency symptoms, and the mechanism of B uptake and transport under limited B conditions. B deficiency can be mitigated by inorganic fertilizer supplementation, but the deleterious impact of frequent fertilizer application disrupts soil fertility and creates environmental pollution. Considering this, we have summarized the available information regarding alternative approaches, such as root structural modification, grafting, application of biostimulators (mycorrhizal fungi (MF) and rhizobacteria), and nanotechnology, that can be effectively utilized for B acquisition, leading to resource conservation. Additionally, we have discussed several new aspects, such as the combination of grafting or MF with nanotechnology, combined inoculation of arbuscular MF and rhizobacteria, melatonin application, and the use of natural and synthetic chelators, that possibly play a role in B uptake and translocation under B stress conditions.

Environmental Nitrogen Losses from Commercial Crop Production Systems in the Suwannee River Basin of Florida.

The springs and the Suwannee river of northern Florida in Middle Suwanee River Basin (MSRB) are among several examples in this planet that have shown a temporal trend of increasing nitrate concentration primarily due to the impacts of non-point sources such as agriculture. The rate of nitrate increase in the river as documented by Ham and Hatzell (1996) was 0.02 mg N L-1 y-1. Best management practices (BMPs) for nutrients were adopted by the commercial farms in the MSRB region to reduce the amounts of pollutants entering the water bodies, however the effectiveness of BMPs remains a topic of interest and discussion among the researchers, environmental administrators and policy makers about the loads of nitrogen entering into groundwater and river systems. Through this study, an initiative was taken to estimate nitrogen losses into the environment from commercial production systems of row and vegetable crops that had adopted BMPs and were under a presumption of compliance with state water quality standards. Nitrogen mass budget was constructed by quantifying the N sources and sinks for three crops (potato (Solanum tuberosum L.), sweet corn (Zea mays L.) and silage corn (Zea mays L.)) over a four year period (2010-2013) on a large representative commercial farm in northern Florida. Fertilizer N was found to be the primary N input and represented 98.0 ± 1.4, 91.0 ± 13.9, 78.0 ± 17.3% of the total N input for potato, sweet corn, and silage corn, respectively. Average crop N uptake represented 55.5%, 60.5%, and 65.2% of the mean total input N whereas average mineral N left in top 0.3 m soil layer at harvest represented 9.1%, 4.5%, and 2.6% of the mean total input N. Mean environmental N losses represented 35.3%, 34.3%, and 32.7% of the mean total input N for potato, sweet corn, and silage corn, respectively. Nitrogen losses showed a linear trend with increase in N inputs. Although, there is no quick fix for controlling N losses from crop production in MSRB, the strategies to reduce N losses must focus on managing the crop residues, using recommended fertilizer rates, and avoiding late-season application of nitrogen.

The phosphorus cost of agricultural intensification in the tropics.

Agricultural intensification in the tropics is one way to meet rising global food demand in coming decades(1,2). Although this strategy can potentially spare land from conversion to agriculture(3), it relies on large material inputs. Here we quantify one such material cost, the phosphorus fertilizer required to intensify global crop production atop phosphorus-fixing soils and achieve yields similar to productive temperate agriculture. Phosphorus-fixing soils occur mainly in the tropics, and render added phosphorus less available to crops(4,5). We estimate that intensification of the 8-12% of global croplands overlying phosphorus-fixing soils in 2005 would require 1-4 Tg P yr(-1) to overcome phosphorus fixation, equivalent to 8-25% of global inorganic phosphorus fertilizer consumption that year. This imposed phosphorus 'tax' is in addition to phosphorus added to soils and subsequently harvested in crops, and doubles (2-7 Tg P yr(-1)) for scenarios of cropland extent in 2050(6). Our estimates are informed by local-, state- and national-scale investigations in Brazil, where, more than any other tropical country, low-yielding agriculture has been replaced by intensive production. In the 11 major Brazilian agricultural states, the surplus of added inorganic fertilizer phosphorus retained by soils post harvest is strongly correlated with the fraction of cropland overlying phosphorus-fixing soils (r(2) = 0.84, p < 0.001). Our interviews with 49 farmers in the Brazilian state of Mato Grosso, which produces 8% of the world's soybeans mostly on phosphorus-fixing soils, suggest this phosphorus surplus is required even after three decades of high phosphorus inputs. Our findings in Brazil highlight the need for better understanding of long-term soil phosphorus fixation elsewhere in the tropics. Strategies beyond liming, which is currently widespread in Brazil, are needed to reduce phosphorus retention by phosphorus-fixing soils to better manage the Earth's finite phosphate rock supplies and move towards more sustainable agricultural production.

Magnitude of anthropogenic phosphorus storage in the agricultural production and the waste management systems at the regional and country scales.

Based on a systematic review of 17 recent substance flow analyses of phosphorus (P) at the regional and country scales, this study presents an assessment of the magnitude of anthropogenic P storage in the agricultural production and the waste management systems to identify the potential for minimizing unnecessary P storage to reduce the input of P as mineral fertilizer and the loss of P. The assessment indicates that in case of all (6) P flow analyses at the regional scale, the combined mass of annual P storage in the agricultural production and the waste management systems is greater than 50 % of the mass of annual P inflow as mineral fertilizer in the agricultural production system, while this is close to or more than 100 % in case of half of these analyses. At the country scale, in case of the majority (7 out of 11) of analyses, the combined mass of annual P storage in the agricultural production and the waste management systems has been found to be roughly equivalent or greater than 100 % of the mass of annual P inflow as mineral fertilizer in the agricultural production system, while it ranged from 30 to 60 % in the remaining analyses. A simple scenario analysis has revealed that the annual storage of P in this manner over 100 years could result in the accumulation of a massive amount of P in the agricultural production and the waste management systems at both the regional and country scales. This study suggests that sustainable P management initiatives at the regional and country scales should put more emphasis on minimizing unwanted P storage in the agricultural production and the waste management systems.

Impact of human interventions on nutrient biogeochemistry in the Pamba River, Kerala, India.

Anthropogenic inputs nowadays are the major source of nutrients to the coastal area. While a wealth of data exists from high latitude regions, little is known on the amount and composition of nutrient fluxes from densely populated tropical catchments. The South Indian Pamba River is a prime example in this respect because of its manifold human interventions such as the Sabarimala pilgrimage, the largest pilgrim centre in the world and agricultural practices. In order (i) to identify direct cause-effect relationships, (ii) to quantify land use specific nutrient inputs and (iii) to assess the respective impacts water was sampled along the river course during the pre monsoon, south west monsoon and north east monsoon periods in 2010 to 2012. Sampling segments were chosen according to prevailing land use. A socioeconomic survey on agricultural practices was conducted to collect information on the type, time and quantity of fertilizer application. Our results indicate (i) little human activities in the forest segment resulted in a low nutrient yield; (ii) pilgrim activities led to high ammonium and phosphate yields in the temple segment; (iii) specific fertilizer management resulted in moderate and maximum nitrate yields in the respective agriculture segments. Annual NPK fertilizer inputs to the catchment were 95 kg ha(-1) yr(-1).The average yield for the Pamba River catchment amounted to 3.5 kg ha(-1) yr(-1) of DIN and 0.2 kg ha(-1) yr(-1) of phosphate-P. As opposing predictions for densely-populated regions the N and P yields of the Pamba River are moderate to low on a global scale. It highlights the need for land use specific quantitative estimates from tropical regions in order to improve the global database and local water quality management.

Land use as an explanatory factor for potential phosphorus loss risk, assessed by P indices and their governing parameters.

The total level of phosphorus (P) and the distribution of P pools in the topsoil are significantly affected by the excessive application of mineral and organic fertilizers connected with intensive agriculture. This leads to an increased potential risk for P loss, and then contributes to freshwater eutrophication. Soil test P (STP), P sorption index (PSI) and degree of P saturation (DPS) are commonly applied as proxies for assessing the risk of P loss. Although conceptually based, the empirical relationships between these operationally defined proxies and the actual P flux exhibit large spatial variations. Herein, a comprehensive synoptic study and monitoring of soil has been conducted in a watershed in north-eastern China. A set of conventional indicators for soil P loss risk were measured along with the main P pools, P sorption indices, texture, organic matter, as well as Fe and Al oxides and other mineral compositions. Moreover, detailed soil P speciation was conducted using phosphorus nuclear magnetic resonance ((31)P NMR) spectroscopy. In addition, phosphatase activities in the soils were determined for each land use soil category. The results reflected that the soil content of total P, total inorganic P and STP increased significantly following the order of increasing management intensity. STP, being strongly coupled to the application of P fertilizers, was a strong explanatory factor for the spatial differences in DPS - both between and within different land uses. The dominant inorganic and organic P species in the soils were orthophosphate and monoester-P, respectively. Their contents were oppositely correlated with the degree of management influence, with the amount of orthophosphate positively related. Alkaline phosphomonoesterase (AlP) represented the highest activities among the four representative phosphatases, i.e. enzymes that hydrolyze organic P - releasing labile orthophosphate. Orchard soils were found to contain the highest levels of monoester P as well as high AlP activities. This indicates a strong capacity to produce labile orthophosphate. Our results suggest that the type of land use can be employed as a general explanatory factor for considering the potential high risk of loss of P. Regionalized P loss parameters will further improve the accuracy of risk assessment.

Cost-effectiveness and cost-benefit analysis of BMPs in controlling agricultural nonpoint source pollution in China based on the SWAT model.

Best management practices (BMPs) have been widely used in managing agricultural nonpoint source pollution (ANSP) at the watershed level. Most BMPs are related to land use, tillage management, and fertilizer levels. In total, seven BMP scenarios (Reforest1, Reforest2, No Tillage, Contour tillage, and fertilizer level 1-4) that are related to these three factors were estimated in this study. The objectives were to investigate the effectiveness and cost-benefit of these BMPs on ANSP reduction in a large tributary of the Three Gorges Reservoir (TGR) in China, which are based on the simulation results of the Soil and Water Assessment Tool (SWAT) model. The results indicated that reforestation was the most economically efficient of all BMPs, and its net benefits were up to CNY 4.36×10(7) years(-1) (about USD 7.08×10(6) years(-1)). Regarding tillage practices, no tillage practice was more environmentally friendly than other tillage practices, and contour tillage was more economically efficient. Reducing the local fertilizer level to 0.8-fold less than that of 2010 can yield a satisfactory environmental and economic efficiency. Reforestation and fertilizer management were more effective in reducing total phosphorus (TP), whereas tillage management was more effective in reducing total nitrogen (TN). When CNY 10,000 (about USD 162) was applied to reforestation, no tillage, contour tillage, and an 0.8-fold reduction in the fertilizer level, then annual TN load can be reduced by 0.08, 0.16, 0.11, and 0.04 t and annual TP load can be reduced by 0.04, 0.02, 0.01 and 0.03 t, respectively. The cost-benefit (CB) ratios of the BMPs were as follows: reforestation (207 %) > contour tillage (129 %) > no tillage (114 %) > fertilizer management (96 and 89 %). The most economical and effective BMPs can be designated as follows: BMP1 (returning arable land with slopes greater than 25° to forests and those lands with slopes of 15-25° to orchards), BMP2 (implementing no tillage on arable land with slopes less than 15°), and BMP5 (0.8-fold less than that of 2010).

Reduced nutrient pollution in a rural stream following septic tank upgrade and installation of runoff retention measures.

Surface water quality in the UK and much of Western Europe has improved in recent decades, in response to better point source controls and the regulation of fertilizer, manure and slurry use. However, diffuse sources of pollution, such as leaching or runoff of nutrients from agricultural fields, and micro-point sources including farmyards, manure heaps and septic tank sewerage systems, particularly systems without soil adsorption beds, are now hypothesised to contribute a significant proportion of the nutrients delivered to surface watercourses. Tackling such sources in an integrated manner is vital, if improvements in freshwater quality are to continue. In this research, we consider the combined effect of constructing small field wetlands and improving a septic tank system on stream water quality within an agricultural catchment in Cumbria, UK. Water quality in the ditch-wetland system was monitored by manual sampling at fortnightly intervals (April-October 2011 and February-October 2012), with the septic tank improvement taking place in February 2012. Reductions in nutrient concentrations were observed through the catchment, by up to 60% when considering total phosphorus (TP) entering and leaving a wetland with a long residence time. Average fluxes of TP, soluble reactive phosphorus (SRP) and ammonium-N (NH4-N) at the head of the ditch system in 2011 (before septic tank improvement) compared to 2012 (after septic tank improvement) were reduced by 28%, 9% and 37% respectively. However, TP concentration data continue to show a clear dilution with increasing flow, indicating that the system remained point source dominated even after the septic tank improvement.

Effect of nitrogen and phosphorus fertilization on the composition of rhizobacterial communities of two Chilean Andisol pastures.

The effect of nitrogen (N) and phosphorus (P) fertilization on composition of rhizobacterial communities of volcanic soils (Andisols) from southern Chile at molecular level is poorly understood. This paper investigates the composition of rhizobacterial communities of two Andisols under pasture after 1- and 6-year applications of N (urea) and P (triple superphosphate). Soil samples were collected from two previously established sites and the composition of rhizobacterial communities was determined by denaturing gradient gel electrophoresis (PCR-DGGE). The difference in the composition and diversity between rhizobacterial communities was assessed by nonmetric multidimensional scaling (MDS) analysis and the Shannon-Wiener index. In Site 1 (fertilized for 1 year), PCR-DGGE targeting 16S rRNA genes and MDS analysis showed that moderate N application (270 kg N ha(-1) year(-1)) without P significantly changed the composition of rhizobacterial communities. However, no significant community changes were observed with P (240 kg P ha(-1) year(-1)) and N-P application (270 kg N ha(-1) year(-1) plus 240 kg P ha(-1) year(-1)). In Site 2 (fertilized for 6 years with P; 400 kg P ha(-1) year(-1)), PCR-DGGE targeting rpoB, nifH, amoA and alkaline phosphatase genes and MDS analysis showed changes in rhizobacterial communities only at the highest rate of N application (600 kg N ha(-1) year(-1)). Quantitative PCR targeting 16S rRNA genes also showed higher abundance of bacteria at higher N application. In samples from both sites, the Shannon-Wiener index did not show significant difference in the diversity of rhizobacterial communities. The changes observed in rhizobacterial communities coincide in N fertilized pastures with lower soil pH and higher pasture yields. This study indicates that N-P application affects the soil bacterial populations at molecular level and needs to be considered when developing fertilizer practices for Chilean pastoral Andisols.

Release of phosphorus under reducing and simulated open drainage conditions from overfertilised soils.

Does removal of cations from soil solution during soil reduction stimulate phosphorus (P) release? An ion-exchange resin system was employed to provide a sink during the incubation of twelve soils under fully reducing conditions. This experimental design was considered to better simulate the loss of ions likely to occur under field conditions than more routine batch type closed extraction systems where solutes build-up in the extract solution. The small solute concentrations that remain in the equilibrating solution suggest the mixed resin system acted as an effective sink over the whole experimental period. By maintaining a small P concentration the resin system mimics soil drainage conditions and encourages P release from soil. Measurement of soil P forms by sequential extraction after the incubation period indicated an increase in the amorphous forms present. Here we show that even if the P-containing solution is retained by the soil, the potential for a subsequent P loss is increased under aerobic conditions. The management of drainage systems should try and avoid the onset of anaerobic conditions. Eventually, magnesium- and calcium-based precipitation products could recapture P from drains recycling it in topsoils as fertilizer.

The Freundlich adsorption isotherm constants and prediction of phosphorus bioavailability as affected by different phosphorus sources in two Kansas soils.

Phosphorus (P) adsorption onto soil constituents influences P bioavailability from both agronomic and environmental perspectives. In this study, the P availability from different P sources along with utility of Freundlich adsorption coefficients on the predictability of various crop growth parameters were assessed. Two soils were amended with 150mgPkg(-1) each from six different P sources comprised of manures from two types of ruminants animals, three types of monogastric animals, and inorganic P fertilizer. Corn (Zea mays) was grown and harvested seven times under greenhouse conditions to remove P from the P amended treatments. The application of all P sources reduced the value of Freundlich K and increased the value of Freundlich 1/n and equilibrium P concentration (EPC0) in both soils compared to the un-amended control before cropping. The swine (Sus scrofa) manure (HM) resulted in significant smaller values of Freundlich K and larger values of 1/n in the P deficient Eram-Lebo soil compared to other P sources while, the opposite was true for the turkey (Meleagris gallopava) litter (TL) in the Ulysses soil. The corn biomass, tissue P concentration and P uptake were significantly influenced by all P sources during the first harvest and the total P uptake during seven harvests in both soils compared to the control treatment. Both Freundlich coefficients had strong relationships with the aforementioned corn parameters in the P deficient Eram-Lebo soil while, strength of the association was weak or missing in the Ulysses soil which had optimum levels of antecedent P.

Applying physicochemical approaches to control phosphogypsum heavy metal releases in aquatic environment.

One of the most important sources of solid waste in the Mediterranean Basin ecosystem originated from the phosphate fertilizer industries, which discharge phosphogypsum (PG) directly into aquatic environments or are stacked on stockpiles. The present study investigates metal release from PG under the influence of variable pH, increasing PG mass content, and complexing organic matter ligands. Major ions from PG leachates, grain size and charge, main functional groups along with metal leachability (Pb, Cd, Cr, Cu, and Zn) were determined using ion chromatography, laser diffraction, zetameter, Fourier transform infrared spectroscopy, and atomic absorption spectroscopy, respectively. The complete dissolution of PG recorded is at 2 g/L. Saturation and supersaturation with respect to PG may occur at concentrations of 3 and 4 g/L, respectively, revealing a clustering phenomenon leading to heavy metal encapsulation within the aggregates. Organic ligands such as citrate may trigger the cationic exchange within the PG suspension leading to ion release. As these factors are considered as specific process involving the release of contaminants from PG during storage under natural conditions, this study could set the foundations for PG remediation in aquatic environment. Organic ligands under controlled pH conditions could be utilized in treating fertilizer industrial wastes by taking into consideration the particularity of the receiving area, thus decreasing metal hazardous impact on natural media.

Soil phosphorus forms and their variations in selected paddy soils of Iran.

Fractionation of soil phosphorus (P) can provide useful information for assessing the risk of soil P as the potential sources of eutrophication in aquatic systems. Little information exists on P forms in paddy soils of Isfahan Province in central Iran, where P fertilizers have been continuously applied for at least 45 years. The objectives of this study were to investigate concentrations and proportions of P forms in paddy soils and correlate the content of P forms with basic soil properties. Soil samples from three paddy sites were obtained, and soil P forms were determined by a modified Hedley fraction method. Results show that the total P concentrations ranged from 288 to 850 mg kg(-1) and were enriched in site 1. In all sites, the rank order of P fractions was HCl-P (CARB-P) > residual-P (RES-P) > NaOH-P (Fe-Al-P) > KCl-P (EXCH-P), indicating that Ca compounds are the main soil components contributing to P retention in these calcareous paddy soils. The EXCH-P represented on average < 1 % of the total P, while the Fe-Al-P ranged 3.3-18 %. The CARB-P showed considerable contribution (63.6-85.6 %) to the total P. The Pearson correlation matrix indicated that Fe-Al-P only was positively correlated with total P, but did not show any significant correlations with other soil geochemical properties. Calcium-bound P fraction was significantly correlated with the clay, silt, cation exchange capacity, and total P.

Effects of increased nitrogen deposition and rotation length on long-term productivity of Cunninghamia lanceolata plantation in southern China.

Cunninghamia lanceolata (Lamb.) Hook. has been widely planted in subtropical China to meet increasing timber demands, leading to short-rotation practices that deplete soil nutrients. However, increased nitrogen (N) deposition offsets soil N depletion. While long-term experimental data investigating the coupled effects related to short rotation practices and increasing N deposition are scarce, applying model simulations may yield insights. In this study, the CenW3.1 model was validated and parameterized using data from pure C. lanceolata plantations. The model was then used to simulate various changes in long-term productivity. Results indicated that responses of productivity of C. lanceolata plantation to increased N deposition were more related to stand age than N addition, depending on the proportion and age of growing forests. Our results have also shown a rapid peak in growth and N dynamics. The peak is reached sooner and is higher under higher level of N deposition. Short rotation lengths had a greater effect on productivity and N dynamics than high N deposition levels. Productivity and N dynamics decreased as the rotation length decreased. Total productivity levels suggest that a 30-year rotation length maximizes productivity at the 4.9 kg N ha(-1) year(-1) deposition level. For a specific rotation length, higher N deposition levels resulted in greater overall ecosystem C and N storage, but this positive correlation tendency gradually slowed down with increasing N deposition levels. More pronounced differences in N deposition levels occurred as rotation length decreased. To sustain C. lanceolata plantation productivity without offsite detrimental N effects, the appropriate rotation length is about 20-30 years for N deposition levels below 50 kg N ha(-1) year(-1) and about 15-20 years for N deposition levels above 50 kg N ha(-1) year(-1). These results highlight the importance of assessing N effects on carbon management and the long-term productivity of forest ecosystems.

Mitigation of nutrient losses via surface runoff from rice cropping systems with alternate wetting and drying irrigation and site-specific nutrient management practices.

Resource-conserving irrigation and fertilizer management practices have been developed for rice systems which may help address water quality concerns by reducing N and P losses via surface runoff. Field experiments under three treatments, i.e., farmers' conventional practice (FCP), alternate wetting and drying (AWD), and AWD integrated with site-specific nutrient management (AWD + SSNM) were carried out during two rice seasons at two sites in the southwest Yangtze River delta region. Across site years, results indicated that under AWD irrigation (i.e., AWD and AWD + SSNM), water inputs were reduced by 13.4~27.5 % and surface runoff was reduced by 30.2~36.7 % compared to FCP. When AWD was implemented alone, total N and P loss masses via surface runoff were reduced by 23.3~30.4 % and 26.9~31.7 %, respectively, compared to FCP. However, nutrient concentrations of surface runoff did not decrease under AWD alone. Under AWD + SSNM, total N and P loss masses via surface runoff were reduced to a greater extent than AWD alone (39.4~47.6 % and 46.1~48.3 % compared to FCP, respectively), while fertilizer inputs and N surpluses significantly decreased and rice grain yields increased relative to FCP. Therefore, by more closely matching nutrient supply with crop demand and reducing both surface runoff and nutrient concentrations of surface runoff, our results demonstrate that integration of AWD and SSNM practices can mitigate N and P losses via surface runoff from rice fields while maintaining high yields.

Impact of anthropogenic activities on water quality of Lidder River in Kashmir Himalayas.

The pristine waters of Kashmir Himalaya are showing signs of deterioration due to multiple reasons. This study researches the causes of deteriorating water quality in the Lidder River, one of the main tributaries of Jhelum River in Kashmir Himalaya. The land use and land cover of the Lidder catchment were generated using multi-spectral, bi-seasonal IRS LISS III (October 2005 and May 2006) satellite data to identify the extent of agriculture and horticulture lands that are the main non-point sources of pollution at the catchment scale. A total of 12 water quality parameters were analyzed over a period of 1 year. Water sampling was done at eight different sampling sites, each with a varied topography and distinct land use/land cover, along the length of Lidder River. It was observed that water quality deteriorated during the months of June-August that coincides with the peak tourist flow and maximal agricultural/horticultural activity. Total phosphorus, orthophosphate phosphorus, nitrate nitrogen, and ammoniacal nitrogen showed higher concentration in the months of July and August, while the concentration of dissolved oxygen decreased in the same period, resulting in deterioration in water quality. Moreover, tourism influx in the Lidder Valley shows a drastic increase through the years, and particularly, the number of tourists visiting the valley has increased in the summer months from June to September, which is also responsible for deteriorating the water quality of Lidder River. In addition to this, the extensive use of fertilizers and pesticides in the agriculture and horticulture lands during the growing season (June-August) is also responsible for the deteriorating water quality of Lidder River.

Evaluating nutrient impacts in urban watersheds: challenges and research opportunities.

This literature review focuses on the prevalence of nitrogen and phosphorus in urban environments and the complex relationships between land use and water quality. Extensive research in urban watersheds has broadened our knowledge about point and non-point pollutant sources, but the fate of nutrients is not completely understood. For example, it is not known how long-term nutrient cycling processes in turfgrass landscapes influence nitrogen retention rates or the relative atmospheric contribution to urban nitrogen exports. The effect of prolonged reclaimed water irrigation is also unknown. Stable isotopes have been used to trace pollutants, but distinguishing sources (e.g., fertilizers, wastewater, etc.) can be difficult. Identifying pollutant sources may aid our understanding of harmful algal blooms because the extent of the relationship between urban nutrient sources and algal blooms is unclear. Further research on the delivery and fate of nutrients within urban watersheds is needed to address manageable water quality impacts.

Phosphorus concentration and loading reductions following changes in fertilizer application and formulation on managed turf.

Excess phosphorus, particularly in surface waters can lead to severe eutrophication. Identifying source areas, quantifying contributions, and evaluating management practices are required to address current and future water quality concerns. A before-after study was conducted from 2003-2010 on a sub-watershed of Northland Country Club Golf Course in Duluth, MN to demonstrate the impacts of two different phosphorus management approaches (Period 1: traditional application and timing using commercially available synthetic blends; Period 2: reduced rate, low dose applications, and organic formulations). Outflow median dissolved reactive phosphorus (DRP) and total phosphorus (TP) stream concentrations were significantly less in Period 2 compared to Period 1. There was no statistical difference in the mean TP loading in Period 1 (0.25 kg ha(-1) year(-1)) compared to Period 2 (0.20 kg ha(-1) year(-1)) or between the DRP loading in Period 1 (0.15 kg ha(-1) year(-1)) compared to Period 2 (0.09 kg ha(-1) year(-1)). However, by switching to organic phosphorus formulations and reducing application rates by greater than 75%, substantial reduction in DRP and TP concentrations was achieved. Based on these findings it is recommended that turf managers (parks and recreation to golf courses) explore the feasibility of altering their fertility management related to phosphorus by including organic formulations, low dose applications, and overall rate reductions. Additionally, it is recommended that the fertilizer industry develop and make more readily available commercial blends with lesser to zero amounts of phosphorus.