Wet and dry deposition of sulphates and nitrates in Eastern Canada: 1979–1982

Daily air and precipitation chemistry observations at six rural locations in eastern Canada were analyzed to obtain wet and dry deposition. Dry deposition was calculated from air concentrations using deposition velocities originating from a recent literature review and synthesis exercise involving land use types. Total annual deposition ranges for \({\text{SO}}_{\text{4}}^{\text{ = }} \) from 10 to 86 mmol m^?2 and for \({\text{NO}}_{\text{3}}^{\text{ - }} \) excluding N0₂ contributions to dry deposition from 13 to 62 mmol m^?2. Dry deposition accounts for an estimated 22 and 21% of the total \({\text{SO}}_{\text{4}}^{\text{ = }} \) and \({\text{NO}}_{\text{3}}^{\text{ - }} \) deposition, respectively. For \({\text{NO}}_{\text{3}}^{\text{ - }} \) , this fraction increases to 30% if N0₂ concentration to dry deposition is included. There is a marked seasonal variation in total \({\text{SO}}_{\text{4}}^{\text{ = }} \) deposition but not in that of \({\text{NO}}_{\text{3}}^{\text{ - }} \) . Both wet and dry deposition are episodic. 20% of daily events deliver between 47 and 70% of the deposition.     

Effect of nitrogen and sulphur fertilizers and seed inoculation with rhizobium phaseoli on the nitrogen‐sulphur relationships of bean (phaseolus vulgaris L.)

A greenhouse experiment with beans (Phaseolus vulgaris L.) was performed in order to investigate the effect of nitrogen and sulphur application and seed inoculation on the yield, leaf area, distribution of different nitrogen and sulphur fractions and N/S ratio in shoot, fruit and root.

Inoculation of plants together with nitrogen or sulphur application produces an increase in the concentration of total nitrogen and a decrease in the accumulation of nitrate‐nitrogen and sulphate‐sulphur in shoot, fruit and root. Leaf area increased more with nitrogen than with sulphur application while the highest amounts of fruit dry matter were obtained with sulphur application.

N: S ratios obtained were different according to the part of the plant tested. Sulphur fertilization decreased the N: S ratios in shoot, fruit and root. The data obtained indicate that and adequate N: S ratio can insure maximum production of yield.     

Effect of nitrogen form ratio on pansy growth and nutrition and the palatability to white‐tailed deer

Abstract

Pansies are one of the most popular annual bedding plants in the United States. Growth and uptake of essential nutrients as influenced by N‐form ratio was evaluated in pansy as well as what role pansy nutrition plays in the protection of pansy against feeding damage by white‐tailed deer provided by selected repellents. Plants were grown under three N‐form ratios: 100:0, 50:50, and 0:100NO₃:NH₄. Dry weight was highest for pansy treated with 100:0 and lowest for plants treated with 0:100 NO₃:NH₄ Mean quality ratings were 4.07 for pansies grown with 100:0,1.80 for pansies grown with 50:50, and 0.78 for pansies grown with 0:100. Potassium (K), magnesium (Mg), and manganese (Mn) content was lower in plants treated with 0:100 than in those treated with 100:0. Ammonium may have competed with these cations for uptake. Boron (B), copper (Cu), molybdenum (Mo), and aluminum (Al) content was highest in plants treated with N‐NH₄. There was no significant difference shown in nutrient levels caused by repellent treatments. Feeding damage was shown to be affected by N‐form ratio only on Day 3 of the study. Of the three repellent treatments [Deer and Rabbit Repellent (Thiram), Deer Away purrescent egg spray, and no spray], Thiram provided the greatest protection to pansies over the study period.     

Impacts of altitude and position on the rates of soil nitrogen mineralization and nitrification in alpine meadows on the eastern Qinghai–Tibetan Plateau,China

Alpine and tundra grasslands constitute 7% world terrestrial land but 13% of the total global soil carbon (C) and 10% of the global soil nitrogen (N). Under the current climate change scenario of global warming, these grasslands will contribute significantly to the changing global C and N cycles. It is important to understand the controlling factors on soil N cycling in these ecosystems. To evaluate climate effects on N cycling, soil N mineralization and nitrification rates (0–15 cm) were measured using an in situ closed-top tube incubation across altitudes and positions from 2006 to 2008 in alpine meadows. The data indicated that soil N mineralization and nitrification rates decreased with increasing altitude, but only significantly (P < 0.05) between the lowest and the two higher altitudes. Soil N mineralization and nitrification rates of south-facing slopes were higher than north-facing slopes at each altitude. This suggests that soil temperature and soil water content (WC) were the controlling factors for soil N mineralization and nitrification rates across altitude with soil WC being the most important factors over positions. Soil nitrification rate depended on soil N mineralization rate, and both rates may increase in response to regional warming of the alpine meadow.     

Electronic Journal of Extension: From Hard Copy to Electronic Format–An Evaluation of a Pilot Test

ABSTRACT

In 1992 the Journal of Extension's Board of Directors authorized a pilot project to test the feasibility of producing and distributing the Journal electronically as a means of reducing the direct and indirect costs of publication. The University of Wisconsin-Extension headed the pilot test and the University of Missouri-Extension was asked to conduct a comprehensive evaluation of the electronic Journal of Extension. This article describes the purposes, methods, content, and preliminary findings of the evaluation of this pilot project.     

The deposition and fate of spawn clumps of the common frog Rana temporaria at a site in Cambridgeshire, 1971–1983

Deposition and fate of spawn clumps of the frog Rana temporaria have been monitored on St Neots Common, Cambridgeshire from 1971 to 1983. On a part of the Common subject to considerable public pressure, collection accounted for an average of about 20% of the clumps per annum (range 8–80%). This part contains several water bodies that usually dry out during the tadpole season as well as some that persist, and an average of roughly 20% of the clumps (range 0–58%) hatched in sites which subsequently desiccated. On the less disturbed part of the Common, collection was relatively unimportant, while desiccation losses, because of the uncertain persistence of one particularly attractive site, tended to be either nil or virtually catastrophic. On the Common as a whole, collection was the most important factor influencing survival of spawn to hatching. In the mid-1970s, 35–50% of the spawn was collected per annum, this being a period when the population appeared to be at a depressed level following a decline from 1972 to 1973. The population recovery during the late 1970s and early 1980s was associated with collection pressure of less than 25% of the clumps per annum.     

Effects of freeze–thaw cycles and the soil water content on carbon and nitrogen changes in different soil types of Heilongjiang Province,China

To reveal the influence of freeze–thaw cycles (FTCs) on soil carbon and nitrogen changes, six typical soils in Northeast China were selected as the research objects to conduct a FTC simulation test in an artificial climate chamber. Three soil volumetric water contents (10%, 20%, 30%) and eight FTCs (0, 2, 4, 6, 8, 10, 15, 20) were set. The results showed that the soil organic carbon (SOC) and microbial biomass carbon (MBC) contents of different soil types under the FTCs initially exhibited a downward and then an upward trend, while the dissolved organic carbon (DOC) content exhibited an upward and then a downward trend. Otherwise, the fourth and sixth FTCs were the key points of change. The SOC, MBC and DOC contents in paddy fields were higher than those in dry fields, showing upward and then downward trends spatially from northeast to southwest. The SOC and MBC contents in each soil type were the highest at the 20% water content, and the DOC content gradually increased with increasing water content. The ammonium nitrogen (NH₄⁺-N) content in different soil types at different water contents under the FTCs showed an upward trend first, then a downward trend and finally an upward trend. The NH₄⁺-N content in paddy fields was higher than that in dry fields. The nitrate nitrogen (NO₃^‒-N) content showed a downward trend first, then an upward trend and finally a downward trend. The NO₃^‒-N content in dry fields was higher than that in paddy fields. The NH₄⁺-N contents in the three soil types on the Sanjiang Plain were significantly higher than those on the Songnen Plain. The NH₄⁺-N and NO₃^‒-N contents showed upward trends with increasing water content, but the differences were not significant. The results have implications for the study of different types of soils and provide references for research on the mechanism of soil carbon and nitrogen transformation in typical farming areas in Northeast China.     

Evaluation of press mud cake as a source of nitrogen and phosphorus for rice–wheat cropping system in the Indo-Gangetic plains of India

Press mud cake (PMC) is an important organic source available for land application in India. Adequate information regarding availability of nitrogen and phosphorous contained in PMC to rice–wheat (RW) cropping system is lacking. In field experiments conducted for 4 years to study the effect of PMC application to rice as N and P source in RW system, application of 60 kg N ha⁻¹ along with PMC (5 t ha⁻¹) produced grain yield of rice similar to that obtained with the 120 kg N ha⁻¹ in unamended plots. In the following wheat, the residual effects of PMC applied to preceding rice were equal to 40 kg N and 13 kg P ha⁻¹. Immobilization of soil and fertilizer N immediately after the application of PMC was observed in laboratory incubation. The net amount of N mineralized from the PMC ranged from 16% at 30 days to 43% at 60 days after incubation. Available P content in the soil amended with PMC increased by about 60% over the unamended control within 10 days of its application. The P balance for the no-PMC treatment receiving recommended dose of 26 kg P ha⁻¹ year⁻¹ was −13.5 kg P ha⁻¹ year⁻¹. The P balance was positive (+42.3 to 53.5 kg P ha⁻¹ year⁻¹) when PMC was applied to rice. Application of PMC increased total N, organic carbon, and available P contents in the soil.     

Recent advances in the chemistry of nitrogen,phosphorus and potassium as fertilizers in soil: A review

The advent of civilization has made humans dependent on plants for food and medicine, leading to the intensification of agricultural production. The intense cultivation of crops has resulted in the depletion of available nutrients from soil, thereby demanding the application of excess nutrients to soil to improve yield. Thus, mineral fertilizer discovery and application have, in many ways, contributed greatly to meeting global food demands. However, aside from the positive effects of mineral fer...     

Cropland soil–plant systems control production and consumption of methane and nitrous oxide and their emissions to the atmosphere

Croplands are an important source of atmospheric methane (CH₄) and nitrous oxide (N₂O), both potent greenhouse gases. Reduction of cropland CH₄ and N₂O emissions is expected to mitigate climate change. However, large uncertainty remains in the assessment and prediction of these emissions, which prevents us from establishing appropriate mitigation options and strategies. The uncertainty is attributed mainly to the high spatiotemporal variability in emissions (e.g., emission spikes of N₂O). Understanding and quantifying how hotspots of CH₄ and N₂O production in soil and then hot moments of their emissions occur would help reduce the uncertainty. This review focuses on soil–plant systems, particularly the rhizosphere, as possible hotspots of production and consumption of CH₄ and N₂O. It is well known that the rhizosphere controls CH₄ emission strongly, though each process of production and consumption remains to be quantified. On the other hand, surprisingly little attention has been paid to N₂O, besides the fact that plant roots strongly control nitrification and denitrification. We review the current knowledge of cropland CH₄ and N₂O emissions, and conclude that soil–plant interactions strongly affect cropland emissions of both gases, in which functions of plant roots affecting biogeochemical factors (e.g., availability of oxygen, labile organic carbon and inorganic nitrogen) in the rhizosphere and phenological changes are particularly important. In relation to the status of current knowledge, we discuss future research needed.     

Genotypic differences in the antioxidant and carbon–nitrogen metabolism of acid-tolerant and acid-sensitive rice (Oryzasativa L.) cultivars under acid stress

A pot experiment was conducted to investigate differences in antioxidative defence and carbon–nitrogen metabolism between acid-tolerant (YJSM) and acid-sensitive (YHSM) rice cultivars under acid stress. Acid-tolerant and acid-sensitive rice were planted in both acidic soil (pH 4.21) and normal soil (pH 6.13). Forty-eight days after sowing, rice shoots and roots from four treatments were collected, and the other four replicates were harvested at seed maturity. The results revealed that the grain yield of acid-tolerant YJSM was significantly higher than that of acid-sensitive YHSM under acid stress. The activities of antioxidant enzymes (superoxide dismutase and catalase) and contents of non-enzymatic antioxidants (ascorbate and reduced glutathione) of acid-tolerant YJSM were both higher than those of acid-sensitive YHSM under acid stress. Moreover, the enzyme activities (nitrate reductase, glutamine synthetase, glutamate synthase and glutamate dehydrogenase) and product contents (soluble sugar and soluble protein) of carbon–nitrogen metabolism of acid-tolerant YJSM were higher than those of acid-sensitive YHSM under acid stress. The NO₃^–N and carbon (C) contents in leaves of acid-tolerant YJSM were both significantly higher than those of acid-sensitive YHSM under acid stress. This study suggests that the acid-tolerant rice cultivar has better antioxidative defence and carbon–nitrogen metabolism systems than the acid-sensitive rice cultivar and is more effective in resisting acid stress.     

Evaluation of Crop Responses to Applied Fertilizer Phosphorus and Derivation of Optimum Recommendations using the Mitscherlich–Bray Equation

Abstract

In this article, the responses of three important crops (rice, wheat, and soybeans) to applied phosphorous (P) were examined and economically optimum P fertilizer recommendations using the Mitscherlich–Bray model were derived for the three crops at four locations in India. Crop‐yield responses were related to extractable P concentrations estimated by the Olsen method, employing a modification of Mitscherlich's equation. The parameters were considered reliable enough to use for the estimation of fertilizer recommendations at different fertilizer cost–price ratios (p) and marginal rate of return (R). The b parameter value explains how much soil P can substitute for fertilizer P. Thus, for each incremental unit of extractable P, fertilizer P could be reduced by 2.0, 2.9, 1.5, and 1.5 kg P/ha for rice (Periyar), rice (Bhubaneswar), wheat (Hisar), and soybean (Raipur), respectively. Optimum fertilizer rates for rice, wheat, and soybean were generated for different soil P fertility levels. There is also need for such information for other soils and crops.     

Tripartite symbiosis of Pisum–Glomus–Rhizobium leads to enhanced productivity,nitrogen and phosphorus economy,quality, and biofortification in garden pea in a Himalayan acid Alfisol

The present study was carried out to assess nitrogen (N) and phosphorus (P) economy, quality, and productivity of garden pea (Pisum sativum L.) through dual-inoculation of arbuscular mycorrhizal fungi (AMF) and Rhizobium in an acid Alfisol. Experiment was laid out in randomized block design replicated thrice comprising 13 treatments viz. Rhizobium along with three graded N levels (25%, 50%, and 75% soil-test-based recommended N), AMF along with three graded P levels (25%, 50%, and 75% soil-test-based recommended P), dual-inoculation of AMF and Rhizobium conjoint with four graded N and P levels (25%, 50%, 75%, and 100% soil-test-based recommended N and P), and three other treatments viz. generalized recommended NP potassium (K) dose (GRD), farmers' practice, and absolute control. The results revealed that dual-inoculation of AMF and Rhizobium enhanced the pea productivity, macronutrient (NPK) and micronutrient iron, copper, zinc, and manganese (Fe, Cu, Zn, and Mn) concentrations, and their uptake besides enhancing garden pea quality. Also, dual-inoculation of both symbionts at 75% and 100% soil-test-based N and P dose behaved statistically alike with respect to pea pod yield, NPK uptake, and quality parameters like total soluble solids (TSS) and crude protein (CP), thus indicating an economy of about 25% soil-test-based N and P dose through co-inoculation. AMF and Rhizobium dual-inoculated treatments led to enhanced TSS and CP in pea pods by 4.2% and 6.2%, respectively, over GRD, while sole application of AMF- or Rhizobium-imbedded treatments could enhance these quality parameters by 2.1% only in each case. Similarly, the highest N and P response ratio was registered in dual-inoculated treatments. Overall, dual-inoculation of AMF and Rhizobium with 75% soil-test-based N and P dose in pea can save up to 25% fertilizer N and P dose in acid Alfisol.Also, this tripartite symbiosis besides enhancing pea quality led to better bio-fortified pea seeds with micronutrients especially Fe and Zn, which can greatly curtail the widespread anemia and Zn deficiency in humans living in Himalayan acid Alfisol.     

Response of wheat cultivars to different soil nitrogen and moisture regimes: II. Nitrogen up‐take,partitioning and influx 1

Nitrogen (N) is one of the major mineral nutrients required for growth and development of plants. Soil water availability, N concentration at the root surface and the ability of plants to absorb N are the most important factors that affect N uptake and partitioning. The objective of this study was to use greenhouse and growth chamber environments to investigate how two contrasting water regimes (stress and nonstress) and different soil N concentrations affect the uptake and distribution of N among different plant parts of three cultivars of wheat (Triticum aestivum L.) at different stages of development Results showed that at the beginning of stem elongation and under non N limiting conditions, there was a high and positive correlation between shoot dry matter production and shoot N content. Under N deficient soils that received different N rates, shoot N content was more related to shoot N concentration than to dry matter. Root growth and N content of the ‘Saada’ cultivar were negatively affected by high soil N concentration. Under mild water stress or nonstressed conditions, N uptake by the shoot increased with increased soil N in all cultivars. Overall, severe water stress masked the effect of N supply, and decreased N uptake in the case of ‘Merchouch 8’ and ‘Saada’. Root N content was not affected by water stress but increased when N was supplied. At anthesis and after rewatering plants from boot stage to anthesis, the plants fully recovered, and those that were water stressed, increased their N absorption to a rate much higher than those that were stressed. Nitrogen influx (NI) decreased with water stress, but increased more with increased soil N under well watered conditions than under stress. “Merchouch 8’ had higher NI than ‘Saada’. From this study we can conclude that the effect of N supply on N content was masked by severe water stress, and ‘Nesma’ was less sensitive to this stress. At anthesis, plants that were previously water stressed increased their rate of N uptake during the recovery. Root N was not affected by water stress but increased when soil N was increased.     

Ecological sustainability and the use of chemicals: Is ecotoxicological risk assessment doing its job properly? An introduction to chemical time bombs

Ten million chemical substances are registered scientifically, but only 1 per cent, 100000, are known to be traded internationally, and only a fraction of these are assessed to establish (eco)toxicological risks through international and national authorities. Only a few of the substances are natural or systemic; most are xenobiotic and poorly evaluated with respect to their environmental effects. It is not only the chemical accidents that make newspaper headlines, but the creeping accumulation of pollutants in soils, sediments and groundwater which degrade the environment for future generations. Ecotoxicological risk assessment still neglects this ‘hidden pollution’, as it usually deals only with the bioavailable fractions of chemicals in the environment. the ‘lost’ (residue) fractions, however, can have non-linear and time-delayed effects (chemical time bombs). As governments need to protect their natural resources (soils, sediments, groundwaters) against negative impacts from chemicals, an ecosystem approach May, help them to overcome the shortsightedness of current ‘acute’ ecotoxico-logical risk assessments. the Netherlands' risk philosophy on chemicals in the environment is discussed as an example. the National Environmental Policy Plan-2 (1994) stresses the chain of events associated with a chemical from the raw material, The side effects of its transport, production, use and disposal, to its final effects in the ecosystem, including the time-delayed responses of pollution. a revised ecotoxicological assessment policy under the new NEPP will have to take account of such chemical time bombs.     

Exposure to Bisphenol B Disrupts Steroid Hormone Homeostasis and Gene Expression in the Hypothalamic–Pituitary–Gonadal Axis of Zebrafish

Bisphenol B (BPB) exhibited higher estrogenic activity and anti-androgenic effects than bisphenol A (BPA) in vitro assays. This result indicates that BPB has higher priority for entry into expensive and stressful testing on animals. However, the disrupting mechanisms of BPB on steroid hormone signaling pathway by in vivo assay have not been investigated yet. In this study, the potential disrupting mechanisms of BPB on the hypothalamic–pituitary–gonadal (HPG) axis and liver were probed by employing the Organization for Economic Co-operation and Development (OECD) 21-day short-term fecundity assay with zebrafish. We found that BPB exposure (1 mg/L) could impair the reproductive function of zebrafish and decline the egg numbers, hatching rate, and survival rate. This finding is related to modifications of the testis and ovary histology of the treated zebrafish. The homogenate T levels in male zebrafish decreased in a concentration-dependent manner, and the E2 level significantly increased when exposed to 0.01, 0.1, and 1 mg/L BPB. Real-time polymerase chain reaction (PCR) was performed to examine the gene expressions in the HPG axis and liver. Hepatic vitellogenin (vtg) expression was upregulated in all exposure males, suggesting that BPB possesses estrogenic activity. The disturbed hormone balance was contributed by the significant alteration of the genes along the HPG axis. These alterations suggest that BPB can lead to adverse effects on the endocrine system of teleost fish, and these effects were more prominent in males than in females.