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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]

We analyzed soil prokaryotic and fungal community composition in soils with varying histories of cattle manure application. The manure treatments were (i) annual application for 43 years (MF), (ii) annual application for 14 years followed by 29 years without application (MF14), and (iii) annual application for 30 years followed by 13 years without application (MF30). An annual application of chemical nitrogen (N) fertilizer (CNF) and a non-amended control (Con) were also included. Soil prokaryotic evenness and diversity significantly decreased in MF relative to other treatments in fall, but were similar to the other fertilizer treatments in spring and summer. Distinct prokaryotic and fungal community composition was observed in MF compared to other treatments across fall, spring, and summer seasons. The MF treatment significantly increased the relative abundance of Firmicutes, Gammaproteobacteria, and Gemmatimonadetes, but significantly decreased the relative abundance of Acidobacteria. In fall, the soil prokaryotic and fungal community composition with MF30 was significantly different than the other fertilization treatments. Overall, the study showed that annual manure application (MF) led to a different microbial community composition than the other fertilizer treatments. Soil without manure application for 13 years (MF30) had a significantly different microbial community composition from other fertilizer treatments in fall, while the soil without manure application for 29 years (MF14) resembled a microbial community that had never received manure. [ABSTRACT FROM AUTHOR]

Application of chemical fertilizer or manure can affect soil microorganisms directly by supplying nutrients and indirectly by altering soil pH. However, it remains uncertain which effect mostly shapes microbial community structure. We determined soil bacterial diversity and community structure by 454 pyrosequencing the V1-V3 regions of 16S rRNA genes after 7-years (2007-2014) of applying chemical nitrogen, phosphorus and potassium (NPK) fertilizers, composted manure or their combination to acidic (pH 5.8), near-neutral (pH 6.8) or alkaline (pH 8.4) Eutric Regosol soil in a maize-vegetable rotation in southwest China. In alkaline soil, nutrient sources did not affect bacterial Operational Taxonomic Unit (OTU) richness or Shannon diversity index, despite higher available N, P, K, and soil organic carbon in fertilized than in unfertilized soil. In contrast, bacterial OTU richness and Shannon diversity index were significantly lower in acidic and near-neutral soils under NPK than under manure or their combination, which corresponded with changes in soil pH. Permutational multivariate analysis of variance showed that bacterial community structure was significantly affected across these three soils, but the PCoA ordination patterns indicated the effect was less distinct among nutrient sources in alkaline than in acidic and near-neural soils. Distance-based redundancy analysis showed that bacterial community structures were significantly altered by soil pH in acidic and near-neutral soils, but not by any soil chemical properties in alkaline soil. The relative abundance (%) of most bacterial phyla was higher in near-neutral than in acidic or alkaline soils. The most dominant phyla were Proteobacteria (24.6%), Actinobacteria (19.7%), Chloroflexi (15.3%) and Acidobacteria (12.6%); the medium dominant phyla were Bacterioidetes (5.3%), Planctomycetes (4.8%), Gemmatimonadetes (4.5%), Firmicutes (3.4%), Cyanobacteria (2.1%), Nitrospirae (1.8%), and candidate division TM7 (1.0%); the least abundant phyla were Verrucomicrobia (0.7%), Armatimonadetes (0.6%), candidate division WS3 (0.4%) and Fibrobacteres (0.3%). In addition, Cyanobacteria and candidate division TM7 were more abundant in acidic soil, whereas Gemmatimonadetes, Nitrospirae and candidate division WS3 weremore abundant in alkaline soil. We conclude that after 7-years of fertilization, soil bacterial diversity and community structure were shaped more by changes in soil pH rather than the direct effect of nutrient addition. [ABSTRACT FROM AUTHOR]

Effectively utilizing composts requires that their nitrogen (N) and phosphorus (P) contents be used as fertilizer, but how this is best accomplished is not fully understood. The authors' objective was to quantify N and P availability of a calcareous clay loam soil receiving composts derived from four contrasting beef cattle feedlot feedstocks applied at 50, 150, and 450 mg total P kg−1and supplemented twice with fertilizer N for a 42-week greenhouse plant bioassay. Three composted manures from beef cattle fed distinct diets and a composted mix of slaughterhouse and construction waste were applied. Inorganically fertilized and non-amended soils were included as controls. Canola (Brassica napusL.) and pea (Pisum sativumL.) were grown in pots containing 1.5 kg air-dried soil for six alternating 7-week cycles. Soils amended with composted manure from beef cattle fed typical finishing diets had the lowest apparent N recovery (31%) and the greatest soil nitrate after 42 weeks (25 mg N kg−1). Phosphorus availability was greater with composted manure from beef cattle fed distillers' dried grains than composted manure from beef cattle fed typical finishing diets and a composted mixture of slaughterhouse and construction waste. Apparent P recovery (66%) was greatest from composted manure of beef cattle fed corn (Zea maysL.) distillers' dried grains applied at 50 mg total P kg−1. Composted manure from beef cattle fed distillers' dried grains had greater P availability than conventional composted beef cattle feedlot manure. Overall, performance of the composted mixture of slaughterhouse and construction waste was similar to the composted beef cattle manures. [ABSTRACT FROM AUTHOR]

As biogas production expands, digestates from that industry are increasingly available as potential nutrient sources for crop production, but their agronomic value is poorly understood. Thus, a 5-yr field experiment was conducted to determine the agronomic values of anaerobically digested solid beef cattle feedlot manure (ADM) and the separated solids (SS) from ADM under a semiarid reduced-tillage dryland barley (Hordeum vulgare L.) forage cropping system. Three organic amendments, ADM, SS and undigested solid beef cattle feedlot manure (CM), were applied annually at 200 or 400 kg total N ha-1 for 4 yr, while the residual effect was examined in the fifth year. The higher N and P availability in ADM translated into greater barley forage yields, total N uptake, amendment-derived N uptake, and apparent N recovery (ANR) from ADM-amended soil than SS- and CM-amended soils, while there were no significant differences between soils receiving SS or CM. The ANR was 22% for ADM but only 12% for CM and 9% for SS. In contrast, P uptake, the fraction of amendment-derived P uptake, and apparent P recovery were similar among all amendments. Similar yields, ANR, post-harvest soil NH4, NO3 and Olsen-P concentrations between SS- and CM-amended soils suggest that they have a comparable agronomic value. Less residual Olsen-P in soil receiving ADM than SS or CM suggests that ADM is a lower risk for P accumulation when applied at N-based rates. We recommend that current agronomic values for cattle feedlot manure could be applied to SS but not ADM. [ABSTRACT FROM AUTHOR]

Soil test indicators are needed to predict the contribution of soil organic N to crop N requirements. Labile organic matter (OM) fractions containing C and N are readily metabolized by soil microorganisms, which leads to N mineralization and contributes to the soil N supply to crops. The objective of this study was to identify labile OM fractions that could be indicators of the soil N supply by evaluating the relationship between the soil N supply, the C and N concentrations, and C/N ratios of water extractable OM, hot-water extractable OM, particulate OM, microbial biomass, and salt extractable OM. Labile OM fractions were measured before planting spring wheat ( Triticum aestivum L.) in fertilized soils and the soil N supply was determined from the wheat N uptake and soil mineral N concentration after 6 weeks. Prior to the study, fertilized sandy loam and silty clay soils received three annual applications of 90 kg available N (ha · y)−1 from mineral fertilizer, liquid dairy cattle manure, liquid swine manure or solid poultry litter, and there was a zero-N control. Water extractable organic N was the only labile OM fraction to be affected by fertilization in both soil types ( P < 0.01). Across both test soils, the soil N supply was significantly correlated with the particulate OM N ( r = 0.87, P < 0.001), the particulate OM C ( r = 0.83, P < 0.001), and hot-water extractable organic N ( r = 0.81, P < 0.001). We conclude that pre-planting concentrations of particulate OM and hot-water extractable organic N could be early season indicators of the soil N supply in fertilized soils of the Saint Lawrence River Lowlands in Quebec, Canada. The suitability of these pre-planting indicators to predict the soil N supply under field conditions and in fertilized soils from other regions remains to be determined. [ABSTRACT FROM AUTHOR]