Cover crops are well recognized as a tool to reduce NO3− leaching from agroecosystems. However, their effectiveness varies from site to site and year to year depending on soil, cash and cover crop management, and climate. We conducted a meta‐analysis using 238 observations from 28 studies (i) to assess the overall effect of cover crops on NO3− leaching and subsequent crop yields, and (ii) to examine how soil, cash and cover crop management, and climate impact the effect of non‐leguminous cover crops on NO3− leaching. There is a clear indication that nonleguminous cover crops can substantially reduce NO3− leaching into freshwater systems, on average by 56%. Nonlegume–legume cover crop mixtures reduced NO3− leaching as effectively as nonlegumes, but significantly more than legumes. The lack of variance information in most published literature prevents greater insight into the degree to which cover crops can improve water quality. Among the factors investigated, we identified cover crop planting dates, shoot biomass, and precipitation relative to long‐term mean precipitation as potential drivers for the observed variability in nonleguminous cover crop effectiveness in reducing NO3− leaching. We found evidence indicating greater reduction in NO3− leaching with nonleguminous cover crops on coarse‐textured soils and during years of low precipitation (<90% of the long‐term normal). Earlier fall planting and greater nonleguminous shoot biomass further reduced NO3− leaching. Overall, this meta‐analysis confirms many prior studies showing that nonleguminous cover crops are an effective way to reduce NO3− leaching and should be integrated into cropping systems to improve water quality. Core Ideas Nonleguminous cover crops reduced NO3− leaching by 56% over no cover crop controls. Nonlegume–legume mixtures reduced NO3− leaching equivalent to nonlegumes, but significantly more than legumes. Cover crop planting date, shoot biomass, and precipitation affected nonlegume effects on NO3− leaching. Nonlegumes reduced NO3− leaching more effectively on coarse‐textured soils and in drier years. Earlier planting dates and greater shoot biomass enhanced NO3− leaching reductions with nonlegumes.

To gain a better understanding of the global application of soil erosion prediction models, we comprehensively reviewed relevant peer-reviewed research literature on soil-erosion modelling published between 1994 and 2017. We aimed to identify (i) the processes and models most frequently addressed in the literature, (ii) the regions within which models are primarily applied, (iii) the regions which remain unaddressed and why, and (iv) how frequently studies are conducted to validate/evaluate model outcomes relative to measured data. To perform this task, we combined the collective knowledge of 67 soil-erosion scientists from 25 countries. The resulting database, named ‘Global Applications of Soil Erosion Modelling Tracker (GASEMT)’, includes 3030 individual modelling records from 126 countries, encompassing all continents (except Antarctica). Out of the 8471 articles identified as potentially relevant, we reviewed 1697 appropriate articles and systematically evaluated and transferred 42 relevant attributes into the database. This GASEMT database provides comprehensive insights into the state-of-the-art of soil- erosion models and model applications worldwide. This database intends to support the upcoming country-based United Nations global soil-erosion assessment in addition to helping to inform soil erosion research priorities by building a foundation for future targeted, in-depth analyses. GASEMT is an open-source database available to the entire user-community to develop research, rectify errors, and make future expansions.

Core Ideas Effectiveness of EEFs varied greatly with their modes of action, soils, and management factors. NIs, DIs, and CRFs reduced N2O emissions by 38, 30, and 19%, respectively, compared with conventional N fertilizers. NIs increased overall crop yields by 7% compared with conventional N fertilizers. DIs might provide added benefits over NIs in alkaline soils, coarse‐textured soils, and irrigated systems. Enhanced efficiency fertilizers (EEFs) have the potential to reduce N2O emissions and improve crop productivity, but the impact of soil and management conditions on their effectiveness is not clear. We conducted a meta‐analysis to evaluate the effectiveness of different EEF types in reducing N2O emissions in three cereal production systems: rice (Oryza sativa L.), corn (Zea mays L.), and wheat (Triticum aestivum L.). We also compared EEF efficacy across soil and management conditions for corn and wheat systems. Results showed that the effect of EEFs on N2O emissions and crop yields varied greatly with their modes of action, soil types, and management conditions. Nitrification inhibitors (NIs), double inhibitors (DIs: urease plus nitrification inhibitors), and controlled‐release N fertilizers (CRFs) consistently reduced N2O emissions compared with conventional N fertilizers across soil and management conditions (grand mean decreases of 38, 30, and 19%, respectively). The DIs more effectively reduced N2O emissions in alkaline soils than did NIs, but the trend was reversed in acidic soils. Urease inhibitors also reduced N2O emissions compared with conventional N fertilizers in coarse‐textured soils and irrigated systems. Overall crop yields increased by 7% with the addition of NIs alone. Compared with conventional N fertilizers, DIs also increased crop yields in alkaline soils, coarse‐textured soils, and irrigated systems. However, CRFs had no effect on crop yields. Overall, this study suggests that NIs or DIs can reduce N2O emissions while improving crop yields. Growers should select EEFs based on their soil and management conditions to maximize their effectiveness.

Majority of the farmers are unaware of pesticide types, level of poisoning, safety precautions and potential hazards on health and environment. According to the latest estimate, the annual import of pesticides in Nepal is about 211t a.i. with 29.19% insecticides, 61.38% fungicides, 7.43% herbicides and 2% others. The gross sale value accounts US $ 3.05 million per year. Average pesticides use in Nepal is 142 g a.i./ha, which is very low as compared to other Asian counties. The focus of this paper is to analyze the use and application status of pesticides in Nepal to aware the society about adverse effects of chemical pesticides in the environment . Pesticidal misuse is being a serious concern mainly in the commercial pocket areas of agricultural production, where farmers are suffering from environmental pollution. Incidence of poisoning is also increasing because of intentional, incidental and occupational exposure. Toxic and environmentally persistent chemicals are being used as pesticides. Many studies showed that the chemical pollution of the environment has long-term effects on human life. It is therefore essential that manufacture, use, storage, transport and disposal of chemical pesticides be strictly regulated. The Journal of Agriculture and Environment Vol:13, Jun.2012, Page 67-72 DOI: http://dx.doi.org/10.3126/aej.v13i0.7590

Agroecosystem services from cover crop mixtures are linked to aboveground biomass and total N content (kg ha-1). Reported values in the literature, however, vary for aboveground biomass and total N content of cover crop mixtures compared with monocultures. We conducted a meta-analysis using results from 55 site-years from 21 studies conducted in the United States to examine biomass and N content of hairy vetch (Vicia villosa Roth)-cereal rye (Secale cereale L.) mixtures compared with respective monocultures. Overall, hairy vetch-cereal rye mixtures produced 63 and 21% more biomass compared with hairy vetch and cereal rye monocultures, respectively. The N content of hairy vetch-cereal rye mixtures was 150% greater than that of cereal rye monocultures. When the proportion of hairy vetch seeds (by weight) exceeded 46% of the mixture, the mixtures accumulated equivalent or more N than the greatest yielding monocultures (usually hairy vetch). Compared with monocultures, a more consistent positive response of mixtures on biomass and N content was found on coarse-textured soils and following corn (Zea mays L.) rather than soybean [Glycine max (L.) Merr.] harvest. With increasing growing degree days (GDD), the biomass and N content of mixtures decreased relative to hairy vetch monocultures but increased relative to cereal rye monocultures, suggesting better performance of hairy vetch at higher GDD. We conclude that hairy vetch-cereal rye mixtures can produce equivalent or more biomass than both monocultures and accumulate as much N as hairy vetch, and that the relative productivity of mixtures depends on soil type, previous crop, seeding proportion, and GDD.