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Biochar (BC) has been shown to increase the potential for N retention in agricultural soils. However, the form of N retained and its strength of retention are poorly understood. Here, we examined if the N retained could be readily extractable by standard methods and if the amount of N retained varied with BC field ageing. We investigated soil and field-aged BC (BC) particles of a field experiment (sandy soil amended with BC at 0, 15, and 30 t ha) under two watering regimes (irrigated and rain-fed). Throughout the study, greater nitrate than ammonium retention was observed with BC addition in topsoil (0-15 cm). Subsoil (15-30 cm) nitrate concentrations were reduced in BC treatments, indicating reduced nitrate leaching (standard 2 mol L KCl method). The mineral-N release of picked BC particles was examined with different methods: standard 2 mol L KCl extraction; repeated (10×) extraction in 2 mol L KCl at 22 ± 2°C and 80°C (M); electro-ultrafiltration (M); repeated water + KCl long-term shaking (M); and M plus one repeated shaking at 80°C (M). Nitrate amounts captured by BC particles were several-fold greater than those in the BC-amended soil. Compared with M, standard 2 mol L KCl or electro-ultrafiltration extractions retrieved only 13 and 30% of the total extractable nitrates, respectively. Our results suggest that "nitrate capture" by BC may reduce nitrate leaching in the field and that the inefficiency of standard extraction methods deserves closer research attention to decipher mechanisms for reactive N management.

Biochar may serve as a tool to sustainably mitigate climate change via carbon sequestration and by improving soil fertility. Biochar has shown to retain nitrate in its pores, which increases with an organic coating of the inner surfaces and residence time in soil ("aging"). Here we investigated the plant accessibility of the captured nitrate in field-aged biochar, as a prerequisite for developing carbon-based N fertilization techniques with environmental benefits. Based on previous results, we hypothesized that part of the biochar-captured nitrate would remain unavailable for plants. A twofactorial greenhouse experiment was designed, where the N was applied either as Ca(NO 3) 2 or as n captured in field-aged biochar at five increasing N doses to quinoa and perennial ryegrass in pots. Interestingly, the biochar-captured N was as plant available as the mineral nitrate, except for the highest dosage. Refuting our hypothesis, no significant amounts of N were extractable at the end of the study from the biochar-soil mixtures with repeated-extraction protocols. Thus, N captured by biochar may improve the N use efficiency in agriculture. Further research should evaluate the role of biochar particle size, root morphology, mycorrhization, and soil moisture (variations) for nitrate retrieval from biochar particles by plants because the captured biochar N was less available in the field as under present controlled conditions. Abbreviations BC Biochar BC-aged Field-aged biochar Since preindustrial times (ca. 1,750), anthropogenic CO 2 emissions have increased atmospheric CO 2 mixing ratios by approximately 150% to more than 410 ppm to date, at an unprecedented rate of increase of currently 2.24 ppm per year 1. In December 2015, the COP21 stated in the Paris Agreement that humanity intends 'to keep atmospheric temperature rise to well below the 1.5 °C by 2050'. To achieve this goal, it is not only necessary to curb anthropogenic CO 2 emissions drastically within the next 30 years but also to additionally remove about 300 Gt of carbon from the atmosphere until 2,100 (using negative emission technologies, NETs, e.g. 2,3 ; see also www.4per1 000.org). Among various NETs, natural climate solutions (NCS) such as afforestation/reforestation, combustion/pyrolysis 4,5 and soil C sequestration (SOC stock increase; biochar) offer multiple co-benefits, supporting the UN's sustainable development goals (SDGs 3). NCS involving soil management strategies play an important role among the available spectrum of NETs. It is estimated that if the full potential of carbon sequestration in the biosphere (vegetation and soil 155 and 178 Pg respectively

Nitrogen (N) losses are prevalent under South East Asia’s due to high N fertilizer inputs, but low N fertilizer use efficiency. This leaves a large quantity of reactive N at risk of loss to the environment. Biochar has been found to reduce N losses across a variety of soil types, however, there is limited data available for semi-arid climates, particularly at a field-scale. Herein we present an exploration of the biological and chemical enhancement effects observed of a cotton stalk-based biochar on wheat growth and yield under arid field conditions. The biochar was treated with urea-N and biofertilizer (bio-power) in different treatment setups. The six experimental treatments included; (i) a full N dose “recommended for wheat crops in the region” (104 kg N ha−1) as a positive control; (ii) a half N dose (52 kg N ha−1); (iii) a half N dose + biofertilizer (4.94 kg ha−1) as a soil mixture; (iv) a half N dose + biofertilizer as a seed inoculation; (v) a full N dose as broadcast + biochar (5 t ha−1) inoculated with biofertilizer; and (vi) a full N dose loaded on biochar + biofertilizer applied as a soil mixture. The half dose N application or biofertilizer addition as soil mix/seed inoculated/biochar inoculation with biofertilizer caused reduced wheat growth and yield compared to the control (conventional N fertilization). However, co-application of chemically enhanced biochar (loaded with a full N dose) and biofertilizer as soil mixture significantly increased the crop growth rate (CGR) and leaf area index (LAI). A significantly higher crop growth and canopy development led to a higher light interception and radiation use efficiency (RUE) for total dry matter (TDM) and grain yield (11% greater than control) production compared to the control. A greater grain yield, observed for the full N dose loaded on biochar + biofertilizer applied as a soil mixture, is attributed to prolonged N availability as indicated by greater plant and soil N content at harvest and different crop growth stages, respectively. The present study has improved our understanding of how the application of nitrogen loaded biochar and biofertilizer as soil mixtures can synergize to positively affect wheat growth and soil-nitrogen retention under arid environmental conditions.

BackgroundH. pylori infection has been associated with many micronutrient deficiencies. There is a dearth of data from communities with nutritional deficiencies and high prevalence of H. pylori infection. The aim of this study was to determine the impact of H. pylori infection on serum levels of vitamin B12, folate and homocysteine in patients with functional dyspepsia (FD).MethodsOne hundred and thirty-two patients with FD undergoing gastroscopy were enrolled. The serum was analyzed for B12, folate and homocysteine levels before gastroscopy. H. pylori infection was diagnosed by histopathological examination of gastric biopsies and urea breath test. An independent sample t-test and the Mann–Whitney test were used to compare mean serum concentrations of biomarkers between H. pylori-positive and H. pylori-negative groups of patients. A Chi-square test was performed to assess the differences among proportions, while Spearman’s rho was used for correlation analysis between levels of B12 and homocysteine.ResultsThe mean age of the group was 40.3 ± 11.5 (19–72) years. Folate deficiency was seen in 43 (34.6%), B12 deficiency in 30 (23.1%) and hyperhomocysteinemia in 60 (46.2%) patients. H. pylori was present in 80 (61.5%) patients with FD while it was absent in 50 (38.5%). Mean serum levels of B12, folate and homocysteine in the H. pylori-positive group of patients were not significantly different from the levels in the H. pylori-negative group (357 ± 170 vs. 313 ± 136 pg/mL; p = 0.13), (4.35 ± 1.89 vs. 4.42 ± 1.93 ng/mL; p = 0.84); (15.88 ± 8.97 vs. 16.62 ± 7.82 μmol/L; p = 0.24); respectively.B12 deficiency (≤200 pg/mL) was 23.8% in the H. pylori-positive patients versus 22.0% in the H. pylori-negative patients. Folate deficiency (≤3.5 ng/mL) was 33.8% in the H. pylori-positive group versus 36% in the H. pylori-negative group. Hyperhomocysteinemia (>15 μmol/L) was present in 46.2% of H. pylori-positive patients compared to 44% in the H. pylori-negative group. Correlation analysis indicated that serum B12 levels were inversely associated with serum levels of homocysteine in patients with FD (rho = −0.192; p = 0.028).ConclusionsThis study demonstrated an inverse relationship between serum levels of B12 and homocysteine in patients with FD. Moreover, no impact of the presence of H. pylori was found on B12, folate and homocysteine levels in such patients.

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BackgroundCoronary artery disease is very common in Pakistani population. Some of the studies carried out on Western populations have shown a relationship between body iron status as determined by the ratio of concentrations of serum soluble transferrin receptor (sTfR) to ferritin and the risk of acute myocardial infarction (AMI). In order to investigate whether increased body iron status has any relationship with the risk of premature AMI in Pakistani population, a case-control study was carried out.Methodology/Principal findingsIn this case-control study, 203 consecutive AMI patients [146 males and 57 females; age range 18–45 years] admitted to the National Institute for Cardiovascular Diseases, Karachi, were enrolled with informed consent. In addition, 205 healthy controls whose gender and age (within 3 years) matched the patients, and who had a similar socio-economic background were recruited. Fasting venous blood was obtained and assessed for plasma/serum folate, vitamin B12, homocysteine, total cholesterol, triglycerides, LDL-cholesterol, HDL-cholesterol, sTfR and ferritin and blood lead. It was found that serum concentration of ferritin and blood lead levels were significantly higher in AMI patients compared to their age and gender-matched healthy controls (p value <0.05), while the concentrations of vitamin B12 and HDL-cholesterol were significantly lower in AMI patients compared to controls (p value <0.01). The ratio of sTfR to ferritin was significantly lower in AMI patients compared to controls [mean±SD/median (IQR) values 84.7±295/28.9 (38.4) vs 255±836/49.4 (83.8), respectively; p value <0.001]. Compared with the highest quartile of sTfR/ferritin (low body iron status), the OR for the risk of AMI was 3.29(95% CI, 1.54–7.03) for the lowest quartile (quartile 1) when the model was adjusted for vitamin B12 and HDL-cholesterol (p value for trend <0.01).Conclusions/SignificanceThis study shows a positive association between total body iron status and risk of premature AMI in a Pakistani population.