Effectiveness of Various Types of Bio-Activators to Quality of Compost Fertilizer.

<b>Background and Objective:</b> Plant litter or plants that grow naturally and the plant materials of the cultivated plants are quite abundant both in fresh and dry form. In the case of a plant, litter is not processed and left on the surface of the soil as organic material then the process of decomposition and reshuffle requires a long time. The research aimed to find out the effectiveness of bio-activators on the formation and quality of compost fertilizer. <b>Materials and Methods:</b> The study design was used in a factorial pattern with two factors. The First factor is bio-activator consists of four levels, namely: EM-4, PROMI, Orgadec and (EM-4+PROMI+Orgadec). The second factor is organic matter consists of seven levels, namely: <i>Imperata cylindrica</i>, paddy straw, <i>Gliricidia sepium</i> leaves, (<i>Imperata cylindrica</i> + paddy straw), (<i>Imperata cylindrica</i> + <i>Gliricidia sepium</i> leaves), (paddy straw + <i>Gliricidia sepium</i> leaves), (<i>Imperata cylindrica </i>+ paddy straw + <i>Gliricidia sepium</i> leaves). There were 28 treatments, each treatment was repeated three times to obtain 84 treatment units. <b>Results:</b> The result showed that compost fertilizer with Orgadec bio-activator treatment and PROMI is the best quality (pH compost, water content, P-total, N-total, C-organic, C/N ratio). <b>Conclusion:</b> The compost fertilizer with Orgadec bio-activator is the best quality for this research (pH compost, moisture content, P-total, N-total, C-organic, C/N ratio).

Is soil management system really important? comparison of microbial community diversity and structure in soils managed under organic and conventional regimes with some view on soil properties.

The fertility and productive value of soil are closely related to the physical and chemical properties of the soil as well as its biological activity. This activity is related to the intensity of microbially catalysed processes of transformation of organic and mineral substances contained in the soil. These processes are closely correlated with the abundance and biodiversity of soil microorganisms, especially bacteria, and the activity of enzymes produced by them. In this article we have compared some physicochemical properties of soil derived from conventional and organic farms and microbial communities inhabiting these ecosystems. We aim to investigate whether the soil management regime affects the abundance and diversity of these environments in terms of bacteria. Some differences in microbial communities were observed, but the rhizosphere of plants from organic and conventional soils does not harbour separate microbiomes. Albeit, the method of fertilization influences the diversity of soil microorganisms. A greater diversity of bacteria was observed in soils from farms where organic fertilizers were applied. Soil pH and activity of some soil enzymes were also shown to differ between organic and conventional soil cropping systems.

Influence of KCl Fertilizer and Trichoderma on the Growth and Yield of Upland Rice.

<b>Background and Objective:</b> The rate of population growth is not balanced with the rate of increase in national rice production. The attention of the government and researchers in Southeast Sulawesi on upland rice is still very low, even though the potential for increased upland rice production is quite promising. The research aimed to study the influence of KCl fertilizer and <i>Trichoderma </i>spp. on the growth and yield of upland rice. <b>Materials and Methods:</b> The study was conducted in a Randomized Block Design (RBD) consisting of 6 treatments i.e.: without KCl fertilizer and <i>T. asperellum</i> (K₀), KCl 0.15 g/polybag+<i>T. asperellum </i>50 g/polybag (K₁), KCl 0.30 g/polybag+<i> T. asperellum </i>40 g/polybag (K₂), KCl 0.45 g/polybag+<i>T. asperellum </i>30 g/polybag (K₃), KCl 0.60 g/polybag+<i>T. asperellum </i>20 g/polybag (K₄) and KCl 0.75 g/polybag+<i>T. asperellum </i>10 g/polybag (K₅) with 4 replication for each treatment. The data obtained were analyzed by analysis of variance (ANOVA) and conducted further tests with the Duncan Multiple Range Test (DMRT) at a 95% confidence level. <b>Results:</b> The results of the research revealed KCl fertilizer combination with <i>T. asperellum</i> in general, can increase the growth and yield of upland local aromatic red rice. Application of KCl fertilizers as 0.45 g/polybag equivalent to 90 kg ha¹ (K₃) can provide optimal potassium nutrients for vegetative growth of upland rice. <b>Conclusion:</b> The treatment of KCl fertilizer as 0.45 g/polybag with <i>T. asperellum </i>30 g/polybag (K₃) provides growth and yield of upland rice with an average production of4.95 t ha¹.

Effect of Growing Media Composition on the Growth of Areca Nut (Areca catechu L.).

<b>Background and Objective:</b> Every plant needs a suitable growing medium to grow and develop optimally. The growing media provide nutrients and an ideal place for roots to grow and take nutrients. This study aimed to obtain a suitable growing medium composition to increase the growth of areca nut. <b>Materials and Methods:</b> The research was carried out at the Agronomy Laboratory, Faculty of Agriculture, Halu Oleo University, Indonesia from March-September, 2020. Nine treatments of growing media composition in combination with the percentage of soil medium, rice husk charcoal and organic fertilizer used and arranged in a Randomized Block Design (RBD) with three replications. <b>Results:</b> The result showed that the composition of the growing medium has a significant effect on the growth of areca nuts. Growing media using the composition of 25% soil, 25% rice husk charcoal, 50% of organic plus fertilizer (M₅) is the best growing medium composition that can increase the growth of areca nut. Another growing media is composed of 50% soil, 0% rice husk charcoal, 50% organic plus fertilizer (M₂), 50% soil, 50% rice husk charcoal, 25% organic plus fertilizer (M₄), 25% soil, 50% rice husk charcoal, 25% organic plus fertilizer (M₇) and 0% soil, 50% rice husk charcoal, 50% organic plus fertilizer (M₈) can also be an alternative in increasing the growth of areca nut. <b>Conclusion:</b> The composition of the growing medium has a significant effect on the growth of areca nuts seedling. The growing media using the composition of 25% soil, 25% rice husk charcoal and 50% organic plus fertilizer is the best growing medium composition that can increase the growth of areca nut seedling.

Chitosan-silicon nanofertilizer to enhance plant growth and yield in maize (Zea mays L.).

We report a novel chitosan-silicon nanofertilizer (CS-Si NF) wherein chitosan-tripolyphosphate (TPP) nano-matrix has been used to encapsulate silicon (Si) for its slow release. It was synthesied by ionic gelation method and characterized by dynamic light scattering (DLS), fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and atomic absorption spectrophotometry (AAS). The developed CS-Si NF exhibited slow release of Si and promoted gowth and yield in maize crop. Seeds primed with different concentrations of CS-Si NF (0.04-0.12%, w/v) exhibited up to 3.7 fold increased seedling vigour index (SVI) as compared with SiO2. Its foliar spray significantly induced antioxidant-defence enzymes' activities and equilibrated cellular redox homeostasis by balancing O2-1 and H2O2 content in leaf as compared with SiO2. Application of nanofertilizer (0.01-0.16%, w/v) stirred total chlorophyll content (21.01-25.11 mg/g) and leaf area (159.34-166.96 cm2) to expedite photosynthesis as compared with SiO2. In field experiment, 0.08% CS-Si NF resulted in 43.4% higher yield/plot and 0.04% concentration gave 45% higher test weight as compared with SiO2. Fecund and myriad effects of developed nanofertilizer over SiO2 could be attributed to slow/protective release of Si from nanofertilizer. Overall, results decipher the enormous potential of CS-Si NF for its use as a next generation nanofertilizer for sustainable agriculture.

Phosphorus fractions in soil fertilised with organic waste.

The aim of this study has been to evaluate the effect of sewage sludge and composted sewage sludge and municipal waste on the content of various forms of P in soil. The experiment scheme: C, control; NPK; FYM; DGSS, dried and granulated sewage sludge; CSS, composed sewage sludge; CSSS, composted sewage sludge and straw; CMMW, composted mixed municipal waste; CMGW, composted municipal green waste. The content of bound P was determined in the fractions: F1, easily soluble; F2, exchangeable; F3, organic; F4, carbonate; F5, stable organic-mineral and mineral bonds; and F6, residual. The NPK fertilisation as well as the soil fertilisation with organic substances raised the P-total content and of P bound in the fractions: F3, F4, F5 and F6. The highest amount of phosphorus in the studied soil was in fraction F3 (phosphorus in organic compounds) and the lowest in fraction F1 (phosphorus in the ionic form as H2PO4- and HPO42-). Composted sludge and straw introduced into the soil increased the content of readily soluble P (F1), while the NPK effect was reversed. NPK fertilisation and enhancement of soil organic matter (except CSSS, CMGW) led to a reduction of the P content in F2 fraction. The content of available P determined by the Egner-Riehm method depended on the content of C-organic, P-total and CEC soil. Among the determined phosphorus fractions, the content of available P was most strongly correlated with the content of P bound in the carbonate fraction (F4) and residual fraction (F6) and, less strongly, with the organic phosphorus fraction.

Optimal fertigation for high yield and fruit quality of greenhouse strawberry.

Nitrogen (N), phosphorus (P), potassium (K), and water are four crucial factors that have significant effects on strawberry yield and fruit quality. We used a 11 that involved 36 treatments with five levels of each of the four variables (N, P, and K fertilizers and water) to optimize fertilization and water combination for high yield and quality. Moreover, we used the SSC/TA ratio (the ratio of soluble solid content to titratable acid) as index of quality. Results showed that N fertilizer was the most important factor, followed by water and P fertilizer, and the N fertilizer had significant effect on yield and SSC/TA ratio. By contrast, the K fertilizer had significant effect only on yield. N×K fertilizer interacted significantly on yield, whereas the other interactions among the four factors had no significant effects on yield or SSC/TA ratio. The effects of the four factors on yield and SSC/TA ratio were ranked as N fertilizer > water > K fertilizer > P fertilizer and N fertilizer > P fertilizer > water > K fertilizer, respectively. The yield and SSC/TA ratio increased when NPK fertilizer and water increased, but then decreased when excessive NPK fertilizer and water were applied. The optimal fertilizer and water combination were 22.28-24.61 g plant-1 Ca (NO3)2·4H2O, 1.75-2.03 g plant-1 NaH2PO4, 12.41-13.91 g plant-1 K2SO4, and 12.00-13.05 L water plant-1 for yields of more than 110 g plant-1 and optimal SSC/TA ratio of 8.5-14.

Influence of the application of irrigated water-soluble calcium fertilizer on wine grape properties.

The eastern foot of Helan mountain is a famous production area of high-end wine grapes in China. Excessive application of NPK fertilizer induced deficiency in trace elements, such as calcium, and seriously affected the properties of wine grapes. A vineyard in the eastern foot of Helan mountain was selected to investigate the influence of five different concentration treatments of 15 (T1), 30 (T2), 45 (T3), 60 (T4), and 75 (T5) kg·ha-1 of water-soluble calcium fertilizer (Ca(NO3)2·4H2O) application on grape calcium content, yield and fruit properties. The application of calcium fertilizer significantly increased the calcium content in leaves but reduced that in stems and fruits. The highest grape production of 6560.83 kg·ha-1 was achieved at T5 calcium fertilizer application, corresponding to increase of 30.92% than that for the control (CK, normal fertilization) treatment. The minimum titratable acid of 4.63 g·L-1 in grapes was detected at T2 calcium fertilizer application, which was 16.38% lower than CK, however, 13.40% increase in sugar-to-acid ratio was observed at T2. At 45 kg·ha-1 calcium fertilizer concentration, the anthocyanins content was 6.47 mg·L-1, indicating an increase of 53.23% than CK. This study showed that the optimal calcium fertilizer concentration was 30 kg·ha-1 with the lowest °Brix, titratable acidity, anthocyanins, the highest total phenols, reducing sugar, sugar-to-acid ratio, and an acceptable concentration of the soluble sugar and tannins.

Greenhouse Soil Biosolarization with Tomato Plant Debris as a Unique Fertilizer for Tomato Crops.

Intensive greenhouse horticulture can cause various environmental problems. Among these, the management, storage, and processing of crop residues can provoke aquifer contamination, pest proliferation, bad odors, or the abuse of phytosanitary treatments. Biosolarization adds value to any fresh plant residue and is an efficient technique for the control of soil-borne diseases. This study aims to examine an alternative means of managing greenhouse crop residues through biosolarization and to investigate the influence of organic matter on yield and quality of tomato (Solanum lycopersicum, L.) fruit. With this purpose, the following nutritional systems were evaluated: inorganic fertilization with and without brassica pellets (Fert, Fert +, and Fert ++), fresh tomato plant debris with and without brassica pellets (Rest, Rest +, and Rest ++), and no fertilizer application (Control). The addition of organic matter was equal across all the treatments except for the control with regard to yield and quality of the tomato fruit. In light of these results, the application of tomato plant debris to the soil through biosolarization is postulated as an alternative for the management of crop residues, solving an environmental problem and having a favorable impact on the production and quality of tomatoes as a commercial crop.

Obsolete Laws: Economic and Moral Aspects, Case Study-Composting Standards.

From the early days of philosophy, ethics and justice, there is wide consensus that the constancy of the laws establishes the legal system. On the other hand, the rate at which we accumulate knowledge is gaining speed like never before. Due to the recently increased attention of academics to climate change and other environmental issues, a lot of new knowledge has been obtained about carbon management, its role in nature and mechanisms regarding the formation and degradation of organic matter. A multidisciplinary techno-economic assessment of current composting standards and laws that took into account the current state of knowledge about carbon management was carried out as a case study. Economic and environmental damage caused by outdated laws was revealed. In addition, it was found that the introduction of the best composts into the market is permitted, causing additional negative environmental as well as economic impacts.

Towards protecting the Great Barrier Reef from land-based pollution.

The Great Barrier Reef (GBR) is an iconic coral reef system extending over 2000 km along the north-east coast of Australia. Global recognition of its Outstanding Universal Value resulted in the listing of the 348 000 km(2) GBR World Heritage Area (WHA) by UNESCO in 1981. Despite various levels of national and international protection, the condition of GBR ecosystems has deteriorated over the past decades, with land-based pollution from the adjacent catchments being a major and ongoing cause for this decline. To reduce land-based pollution, the Australian and Queensland Governments have implemented a range of policy initiatives since 2003. Here, we evaluate the effectiveness of existing initiatives to reduce discharge of land-based pollutants into the waters of the GBR. We conclude that recent efforts in the GBR catchments to reduce land-based pollution are unlikely to be sufficient to protect the GBR ecosystems from declining water quality within the aspired time frames. To support management decisions for desired ecological outcomes for the GBR WHA, we identify potential improvements to current policies and incentives, as well as potential changes to current agricultural land use, based on overseas experiences and Australia's unique potential. The experience in the GBR may provide useful guidance for the management of other marine ecosystems, as reducing land-based pollution by better managing agricultural sources is a challenge for coastal communities around the world.

Soil contamination in China: current status and mitigation strategies.

China faces great challenges in protecting its soil from contamination caused by rapid industrialization and urbanization over the last three decades. Recent nationwide surveys show that 16% of the soil samples, 19% for the agricultural soils, are contaminated based on China's soil environmental quality limits, mainly with heavy metals and metalloids. Comparisons with other regions of the world show that the current status of soil contamination, based on the total contaminant concentrations, is not worse in China. However, the concentrations of some heavy metals in Chinese soils appear to be increasing at much greater rates. Exceedance of the contaminant limits in food crops is widespread in some areas, especially southern China, due to elevated inputs of contaminants, acidic nature of the soil and crop species or cultivars prone to heavy metal accumulation. Minimizing the transfer of contaminants from soil to the food chain is a top priority. A number of options are proposed, including identification of the sources of contaminants to agricultural systems, minimization of contaminant inputs, reduction of heavy metal phytoavailability in soil with liming or other immobilizing materials, selection and breeding of low accumulating crop cultivars, adoption of appropriate water and fertilizer management, bioremediation, and change of land use to grow nonfood crops. Implementation of these strategies requires not only technological advances, but also social-economic evaluation and effective enforcement of environmental protection law.

Process improvement for regulatory analyses of custom-blend fertilizers.

Chemical testing of custom-blend fertilizers is essential to ensure that the products meet the formulation requirements. For purposes of proper crop nutrition and consumer protection, regulatory oversight promotes compliance and particular attention to blending and formulation specifications. Analyses of custom-blend fertilizer products must be performed and reported within a very narrow window in order to be effective. The Colorado Department of Agriculture's Biochemistry Laboratory is an ISO 17025 accredited facility and conducts analyses of custom-blend fertilizer products primarily during the spring planting season. Using the Lean Six Sigma (LSS) process, the Biochemistry Laboratory has reduced turnaround times from as much as 45 days to as little as 3 days. The LSS methodology focuses on waste reduction through identifying: non-value-added steps, unneeded process reviews, optimization of screening and confirmatory analyses, equipment utilization, nonessential reporting requirements, and inefficient personnel deployment. Eliminating these non-value-added activities helped the laboratory significantly shorten turnaround time and reduce costs. Key improvement elements discovered during the LSS process included: focused sample tracking, equipment redundancy, strategic supply stocking, batch size optimization, critical sample paths, elimination of nonessential QC reviews, and more efficient personnel deployment.

A contribution to set a legal framework for biofertilisers.

The extensive research, production and use of microorganisms to improve plant nutrition have resulted in an inconsistent definition of the term "biofertiliser" which, in some cases, is due to the different microbial mechanisms involved. The rationale for adopting the term biofertiliser is that it derives from "biological fertiliser", that, in turn, implies the use of living microorganisms. Here, we propose a definition for this kind of products which is distinguishing them from biostimulants or other inorganic and organic fertilisers. Special emphasis is given to microorganism(s) with multifunctional properties and biofertilisers containing more than one microorganism. This definition could be included in legal provisions regulating registration and marketing requirements. A set of rules is also proposed which could guarantee the quality of biofertilisers present on the market and thus foster their use by farmers.

A unified method to process biosolids samples for the recovery of bacterial, viral, and helminths pathogens.

For land application, biosolids are classified as Class A or Class B based on the levels of bacterial, viral, and helminths pathogens in residual biosolids. The current EPA methods for the detection of these groups of pathogens in biosolids include discrete steps. Therefore, a separate sample is processed independently to quantify the number of each group of the pathogens in biosolids. The aim of the study was to develop a unified method for simultaneous processing of a single biosolids sample to recover bacterial, viral, and helminths pathogens. At the first stage for developing a simultaneous method, nine eluents were compared for their efficiency to recover viruses from a 100 gm spiked biosolids sample. In the second stage, the three top performing eluents were thoroughly evaluated for the recovery of bacteria, viruses, and helminthes. For all three groups of pathogens, the glycine-based eluent provided higher recovery than the beef extract-based eluent. Additional experiments were performed to optimize performance of glycine-based eluent under various procedural factors such as, solids to eluent ratio, stir time, and centrifugation conditions. Last, the new method was directly compared with the EPA methods for the recovery of the three groups of pathogens spiked in duplicate samples of biosolids collected from different sources. For viruses, the new method yielded up to 10% higher recoveries than the EPA method. For bacteria and helminths, recoveries were 74% and 83% by the new method compared to 34% and 68% by the EPA method, respectively. The unified sample processing method significantly reduces the time required for processing biosolids samples for different groups of pathogens; it is less impacted by the intrinsic variability of samples, while providing higher yields (P = 0.05) and greater consistency than the current EPA methods.

Growth, root formation, and nutrient value of triticale plants fertilized with biosolids.

Biosolids are utilized as nutrient rich fertilizer. Little material is available on benefits to forage crops resulting from fertilization with biosolids. This paper aimed to compare the effects of fertilization with biosolids versus commercial nitrogen fertilizer on growth, root formation, and nutrient value of triticale plants in a greenhouse experiment. Per treatment, five pots were seeded with five triticale seeds each. Treatments included a nonfertilized control, fertilization with 100, 200, 300, 400, and 500 ml biosolids per pot, and fertilization with a commercial nitrogen fertilizer at the recommended application rate and at double that rate. Biomass production, root length, root diameter, nitrogen, phosphorus, and potassium concentration were analyzed at harvest. Fertilization with biosolids increased triticale production (P < 0.001); production was similar for the 100 to 400 mL treatments. Root length, nitrogen, and phosphorus concentration increased, and potassium concentration decreased linearly with application rate. At the recommended rate, biomass production was similar between fertilization with biosolids and commercial fertilizer. However, plants fertilized with commercial fertilizer had considerably longer roots (P < 0.001), higher nitrogen concentration (P < 0.05), and lower potassium concentration (P < 0.01) than those fertilized with biosolids. Our results indicate that at the recommended application rate, biomass production was similar between fertilization with biosolids and with commercial nitrogen fertilizer, indicating the value of biosolids fertilization as a potential alternative.

Sewage sludge ash to phosphate fertilizer by chlorination and thermal treatment: residence time requirements for heavy metal removal.

Heavy metal removal from sewage sludge ash can be performed by mixing the ash with environmentally compatible chlorides (e.g. CaCl2 or MgCl2) and water, pelletizing the mixture and treating the pellets in a rotary reactor at about 1000 degrees C. Thermogravimetry-mass spectroscopy, muffle oven tests (500-1150 degrees C) and investigations in a laboratory-scale rotary reactor (950-1050 degrees C, residence time 1-25 min) were carried out. In the rotary reactor, up to 97% of Cu, 95% Pb and 95% Zn can be removed at 1050 degrees C. As Cl release starts from 400 degrees C (obtained from thermogravimetry-mass spectrometry experiments), heavy metals are already removed partially within the heating period. This heavy metal removal can be described as being similar to a first-order rate law. To meet the limit values specified in the Austrian and German fertilizer ordinances, residence times of the order of minutes are sufficient at 950 degrees C.

Revegetation of a uranium mine dump by using fertilizer treated sessile oaks.

The rehabilitation of contaminated sites and the establishment of suitable trees for revegetation purposes is often problematic due to the mostly suboptimal nutrient supply and the poor humus reservoir. For these reasons hydrogels (Stockosorb) and novel humus substitutes (NOVIHUM), serving as long lasting fertilizer (LLF), were recently tested successfully. At the beginning of this multiyear study, those LLFs were administered to the root zone of young sessile oaks (Quercus petraea (Mattuschka) Liebl.), growing in test trials on a uranium mine dump in Schlema (Germany). To quantify the effect of LLFs on plant vitality, chlorophyll a fluorescence measurements and JIP test analyses were used. The results revealed up to 49% higher average photosynthetic vitality (PI(ABS)) of the LLF treated plants compared to controls. Particularly in the first test year, the efficiency of photosynthetic electron transport was strongly increased. This stimulation of photosynthetic activity was supported by direct measurements showing up to 129% increased diameter growth of the treated plants after a four year experimental period. Furthermore an increase of the maximum water holding capacity of the dump soil was attained by using LLFs. Overall, the findings reported here represent a feasible, ecologically justifiable reforestation method with a low environmental hazard potential.

Trace elements in compost regulation: the case of Spain.

We use the example of the Spanish Decree on Fertilizers (2005) to discuss the need of new horizontal regulations for assessing the quality of all the materials reaching the soil as amendments of fertilizers, in particular in what concerns potentially toxic trace elements in compost. Here it is proposed that the new regulations take into account the following: establishing maximum legal limits for the total loads for each element when compost is added to agricultural soils; establishing the maximum total concentration and bioavailability of each element in the final compost; and that they take into account the soil characteristics for establishing those limits.

Estimation of incidence and social cost of colon cancer due to nitrate in drinking water in the EU: a tentative cost-benefit assessment.

BACKGROUND: Presently, health costs associated with nitrate in drinking water are uncertain and not quantified. This limits proper evaluation of current policies and measures for solving or preventing nitrate pollution of drinking water resources. The cost for society associated with nitrate is also relevant for integrated assessment of EU nitrogen policies taking a perspective of welfare optimization. The overarching question is at which nitrogen mitigation level the social cost of measures, including their consequence for availability of food and energy, matches the social benefit of these measures for human health and biodiversity. METHODS: Epidemiological studies suggest colon cancer to be possibly associated with nitrate in drinking water. In this study risk increase for colon cancer is based on a case-control study for Iowa, which is extrapolated to assess the social cost for 11 EU member states by using data on cancer incidence, nitrogen leaching and drinking water supply in the EU. Health costs are provisionally compared with nitrate mitigation costs and social benefits of fertilizer use. RESULTS: For above median meat consumption the risk of colon cancer doubles when exposed to drinking water exceeding 25 mg/L of nitrate (NO3) for more than ten years. We estimate the associated increase of incidence of colon cancer from nitrate contamination of groundwater based drinking water in EU11 at 3%. This corresponds to a population-averaged health loss of 2.9 euro per capita or 0.7 euro per kg of nitrate-N leaching from fertilizer. CONCLUSIONS: Our cost estimates indicate that current measures to prevent exceedance of 50 mg/L NO3 are probably beneficial for society and that a stricter nitrate limit and additional measures may be justified. The present assessment of social cost is uncertain because it considers only one type of cancer, it is based on one epidemiological study in Iowa, and involves various assumptions regarding exposure. Our results highlight the need for improved epidemiological studies.