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Wastewater has been widely reclaimed to irrigate crops where freshwater resources are scarce. Therefore, predicting the impacts of wastewater irrigation on soil moisture and soil salinity is critical for sustainable wastewater irrigation management. In this study, the denitrification‐decomposition (DNDC) model was modified to couple wastewater irrigation with a water balance equation (SALT‐DNDC). Secondly, the SALT‐DNDC model was verified against the measured soil moisture, temperature, and nitrous oxide emission during the barley‐growing season at Lethbridge, Alberta, Canada. Third, the SALT‐DNDC model was used to predict the effects of one‐time and split wastewater irrigation with varying quantity and quality on transpiration and soil salinity. The results showed that split irrigation of wastewater with an electrical conductivity of 6 dS m−1 reduced the peak soil salinity from 52–55 dS m−1 to a range of 8–20 dS m−1, compared to one‐time irrigation. Therefore, the split irrigation of wastewater could substantially reduce peak soil salinity. In this regard, optimal split wastewater irrigation with elevated salt concentration can limit soil salinity to acceptable salt tolerance levels for crop growth. The SALT‐DNDC model can simulate dynamics of split irrigation wastewater and offers a new tool for assessing the effects of wastewater reuse on soil salinity. [ABSTRACT FROM AUTHOR]

Abstract: Long‐term cattle grazing may degrade grassland soils, but how soil CO2, CH4 and N2O fluxes respond to long‐term cattle grazing is poorly understood. Therefore, we quantified soil CO2, CH4 and N2O fluxes in response to four levels (none, light, heavy, very heavy) of long‐term (>65 years) cattle grazing on a rough fescue grassland in the foothills of the Rocky Mountains, Canada over three grazing seasons. The grazed grassland soils emitted 37 to 51% more CO2 than non‐grazed soils. Grazed grassland soils were small CH4 sinks and small N2O sources each season, and their cumulative fluxes were significantly affected by a cattle stocking rate × year interaction, indicating the grazing effect was influenced by environmental conditions. Soil CH4 uptake was negatively correlated with soil moisture (r = −0·59). The 2013 grazing season had about 41% greater precipitation than average and grazing significantly decreased CH4 uptake 31 to 38% compared with non‐grazed soils. The N2O emissions were 122 to 179% greater with heavy and very heavy grazing than none in the wet season, unaffected by grazing in the normal precipitation season and 72% lower with light grazing than none in the dry season. Predicting trace gas fluxes from grazed grassland soils across space and time is difficult because of interactions among weather conditions, edaphic properties and grazing intensity. However, long‐term cattle grazing increased soil CO2 fluxes, while the grazing effect on CH4 uptake depended on precipitation and the soil N2O flux responded as a function of grazing intensity and precipitation. © 2016 Her Majesty the Queen in Right of Canada. Land Degradation & Development Published by John Wiley & Sons Ltd. [ABSTRACT FROM AUTHOR]

Managing the stocking rate is considered one of the most important practices influencing carbon storage on rangeland. The effects of four stocking rates consisting of a non-grazed control (CK), light (0.15 sheep ha month), moderate (0.30 sheep ha month) and heavy (0.45 sheep ha month) were evaluated for impacts on carbon storage taking place on the Desert Steppe of Inner Mongolia, China. Carbon storage was measure in aboveground vegetation, roots and soil in August of 2009, 2011 and 2013. Both aboveground biomass (AGB) and below-ground biomass (BGB) increased significantly as stocking rate decreased. Stocking rate also had a significant effect on both the aboveground and below-ground carbon storage in plant biomass, but had no effect on the soil carbon. Compared to the heavy stocking rate typically practiced by local herders, lower stocking rates increased the total above- and below-ground biomass carbon storage by ≥ 7%. Over the 3 year study, compared to the moderate stocking rate, the rate of carbon sequestration with a light stocking rate was 0.7 Mg C ha year. Thus, reducing stocking rate has the potential to increase C sequestration and storage, as well as maintaining animal numbers at a more sustainable level suitable for the Desert Steppe ecosystem. [ABSTRACT FROM AUTHOR]

Grassland communities occupy about 25 % of global land area and global warming could alter grassland plant community coverage. A field study was conducted to investigate the impact of soil warming (surface soil temperature increased by 1.3 °C) and nitrogen addition (100 kg N ha year) on a desert steppe community in Inner Mongolia, China, from 2006 to 2011. Although there were strong intra- and inter-annual variations, in general, warming had little effect on coverage of the four major species (two cool season C species: Convolvulus ammannii and Stipa breviflora, and two warm season C species: Cleistogenes songorica and Kochia prostrata) over six growing seasons. The C/C coverage ratio consistently decreased with warming, with the decrease being statistically significant for one-third of sampling dates. Warming caused a reduction (from 27.6 to 25.1 %) in peak season total plant community coverage. N addition did not affect the four main species, four functional groups (perennial grass, perennial forb, shrub and annual-biennial) or the total plant community over the 6 years, except when precipitation was high (231 mm in 2008). The small reduction in plant community coverage demonstrated the resilience of desert steppe to warming. There could be a shift of C to C species because of warming, as indicated by the decrease in C/C ratio, but confirmation of this trend requires further study. [ABSTRACT FROM AUTHOR]

The impact of fertilization on maize ( Zea mays L.) yield and soil properties was investigated in a long-term (> 18 y) experimental field in N China. A completely randomized block design with seven fertilizer treatments and four replications was used. The seven fertilizer treatments were (1) compost (COMP), (2) half compost plus half chemical fertilizer (COMP1/2), (3) balanced NPK fertilizer (NPK), (4-6) unbalanced chemical fertilizers without one of the major elements (NP, PK, and NK), and (7) an unamended control (CK). In addition to maize yield, soil chemical and biological properties were investigated. Compared to the balanced NPK treatment, maize yield from the COMP treatment was 7.9% higher, from the COMP1/2 was similar, but from the NP, PK, NK, and CK treatment were 12.4%, 59.9%, 78.6%, and 75.7% lower. Across the growing season, microbial biomass C and N contents, basal soil respiration, and fluorescein diacetate hydrolysis, dehydrogenase, urease, and invertase activities in the COMP and COMP1/2 treatments were 7%-203% higher than the NPK treatment. Values from all other treatments were up to 60% lower than the NPK treatment. Maize yield is closely related to the soil organic C (OC) and biological properties, and the OC is closely related to various biological properties, indicating that OC is a suitable indicator for soil quality. Our results suggest the most limiting nutrient for improving the yield or soil quality was P, followed by N and K, and balanced fertilization is important in maintaining high crop yield and soil quality. Additionally, increases in OC, N, and biological activities in COMP and COMP1/2 treatments imply that organic compost is superior to the chemical fertilizers tested. [ABSTRACT FROM AUTHOR]

Agricultural land currently is used not only for producing food, fiber, and other bioproducts, but also for disposing of and recycling industrial, municipal, and agricultural wastes. Because such uses may potentially have negative effects on the environment, the fate of applied elements or of those originally present in the soil are under intensive scrutiny. Temporal change in the mass of a given soil element or constituent per unit area typically is calculated as the difference between constituent masses in a fixed soil depth at two sampling times. This method, however, is adequate for only rare cases when soil volume remains unchanged (i.e., when there are no changes in soil bulk density or thickness). Other methods based on "fixed soil mass," "equivalent soil depth," or "cumulative mass coordinate" have been developed to account for bulk density changes but they still do not account for changes in soil mass, such as those associated with waste inputs or soil redistribution through erosion and deposition, or imports and exports. We propose an alternative method based on elevation-based soil sampling to account for the effects of changes in both soil bulk density and soil mass. Unlike methods that assume soil mass remains unchanged, the proposed method would also be applicable to sites with appreciable additions or removals of soil mass or volume. We discuss the merits of elevation-based soil sampling to assess temporal changes in soil constituents, and present an example of its application to a site receiving heavy applications of livestock manure for 30 yr. [ABSTRACT FROM AUTHOR]

The emission of greenhouse gases (GHG) during feedlot manure composting reduces the agronomic value of the final compost and increases the greenhouse effect A study was conducted to determine whether GHG emissions are affected by composting method. Feedlot cattle manure was composted with two aeration methods—passive (no turning) and active (turned six times). Carbon lost in the forms of CO2 and CH4 was 73.8 and 6.3 kg C Mg−1 manure for the passive aeration treatment and 168.0 and 8.1 kg C Mg−1 manure for the active treatment. The N loss in the form of N2O was 0.11 and 0.19 kg N Mg−1 manure for the passive and active treatments. Fuel consumption to turn and maintain the windrow added a further 4.4 kg C Mg−1 manure for the active aeration treatment. Since CH4 and N2O are 21 and 310 times more harmful than CO2 in their global warming effect, the total GHG emission expressed as CO2–C equivalent was 240.2 and 401.4 kg C Mg−1 manure for passive and active aeration. The lower emission associated with the passive treatment was mainly due to the incomplete decomposition of manure and a lower gas diffusion rate. In addition, turning affected N transformation and transport in the windrow profile, which contributed to higher N2O emissions for the active aeration treatment. Gas diffusion is an important factor controlling GHG emissions. Higher GHG concentrations in compost windrows do not necessarily mean higher production or emission rates. [ABSTRACT FROM AUTHOR]

A correction is presented to a calculation error during conversion of the N2O–N to CO2–C equivalent, which appeared within the issue of the periodical.