Information about soil organic matter fraction and enzyme activity responses to agricultural management may help guide decisions that sustain crop productivity and soil health. We measured carbon and nitrogen in bulk soil, mineral-associated organic matter, particulate organic matter, water-extractable organic matter, and the potential activity of β-glucosidase, N-acetyl-β-d-glucosaminadase, acid phosphomonoesterase and arylsulfatase in three cropping systems after: 1) 21-years of conventional- or no-tillage silage corn monoculture (0-20-cm); and 2) six years of nitrogen fertilization with or without nitrification inhibitors and 3) nine years of 100 or 200% the recommended broadcast or fertigation nitrogen rate in two distinct mature highbush blueberry systems (0-15-cm). Soil organic carbon, particulate organic carbon, particulate organic nitrogen, water-extractable nitrogen and arylsulfatase activity were 17%, 38%, 50%, 25% and 68% greater, respectively, with no-tillage than conventional tillage. Particulate organic carbon accumulated with two decades of no-tillage, which increased soil organic carbon without altering mineral-associated organic carbon. Nitrification inhibitors did not impact any soil organic matter fraction or enzyme activity after six years in a mature highbush blueberry system. Broadcasted nitrogen led to higher soil organic carbon than fertigation, but excessive application (200% vs 100% rate) depleted soil organic carbon, accumulated reactive nitrogen and reduced potential activity of N-acetyl-β-d-glucosaminadase, acid phosphomonoesterase and arylsulfatase after nine years in a mature highbush blueberry system. Excessive nitrogen may deplete organic carbon and cause reactive nitrogen accumulation in soil of mature highbush blueberry systems. Intensive agricultural management has trade-offs for carbon and nitrogen cycling that should be balanced with sustainable crop production.

Green manure can enhance soil phosphorus (P) availability. However, mechanisms related to how green manure residues and microbial responses interact to effect transformations of soil P fractions are not fully understood. This study assessed the dynamics of soil-available P, various P fractions, P-cycling enzyme activities, and the communities and abundance of bacteria harboring P-cycling genes in both high P and low P soils in response to legume and non-legume residues, glucose, and an unamended control over a 90 d incubation. This study revealed that green manure residues enhanced soil-available P and microbial biomass P (MBP) content in both high P and low P soils. The green manure residues markedly elevated the abundance of pqqC and phoD genes at day 15 in the high P soil, and day 60 in the low P soil compared to the unamended soil. Legume residues shifted the composition of bacterial communities harboring pqqC and phoD, fostering the proliferation of pivotal P-mobilizing microorganisms like Pseudomonas and Stella within both high P and low P soils. Conversely, non-legume residues predominantly stimulated the growth of Mycobacterium and Stella taxa within the pqqC- and phoD-bearing bacterial communities, respectively. It is evident that green manure residues exert not only a direct influence on soil P fractions through the supply of exogenous P containing compounds, but also have indirect impacts by enhancing microbial P turnover, enzymatic activities linked to P cycling, and the assemblages of pqqC/phoD-bearing bacteria and their relative gene abundances. Our findings underscore the significance of green manure residues in catalyzing shifts in the bacterial community responsible for inorganic phosphate mobilization in the high P soil, as well as the bacterial community associated with alkaline-phosphomonoesterase encoding in the low P soil. This study presents insights into how green manure residues influence transformations of soil P fractions by stimulating soil P-cycling microorganisms to liberate available P in the soil environment.

Cover crops may enhance soil organic carbon (SOC) sequestration, but the links among SOC fractions, microbial necromass carbon (C), and SOC sequestration potential in legume and non-legume cover-cropped orchards are unclear. We leveraged data from seven orchards with varying climatic and edaphic properties in China to assess the effects of legume and non-legume cover crops on SOC and microbial necromass C in bulk soil, particulate organic matter (POM), and mineral-associated organic matter (MAOM). Legume cover crops led to a significantly greater increase in SOC than non-legumes (23 % vs. 2 %), compared with no cover crops. The MAOM-C with legumes and non-legumes were similar but were both significantly greater than the control plots without cover crops. Legume cover crops positively influenced bacterial and fungal necromass C in all SOC fractions, while nonlegume cover crops only affected fungal necromass C in bulk soil and MAOM. The effect of cover crops on the microbial necromass C to SOC ratio was negligible. Fungal necromass contributed most of the microbial necromass C to SOC accumulation, particularly in MAOM. Linear regression showed SOC, POM-C, and MAOM-C accumulated with increasing microbial necromass C. Microbial necromass C was the key factor explaining the variation in POM-C and MAOM-C compared to other climatic and edaphic factors. Partial least squares path modeling showed a causal relationship among cover crops, climate, soil substrates, soil properties, microbial necromass, and SOC and SOC fractions. Our study suggests that changes in microbial necromass C and composition may explain most of the increase in SOC in cover-cropped orchards and that MAOM-C is the principal sink of microbial necromass. This information is valuable for improving our understanding of the potential impact of microbial necromass C on enhancing SOC sequestration potential in orchard soils under cover crop management.

To evaluate how enhanced efficiency liquid nitrogen (N) fertilizers affect winter wheat (Triticum aestivum L.) production under irrigated and rain-fed environments, experiments were conducted at two irrigated and five rain-fed sites across the Canadian Prairies from 2013 to 2018 (22 site-years). The N fertilizers included urea ammonium nitrate (UAN) treated with (i) urease inhibitor N-(n-butyl) thiophosphoric triamide (NBPT), (ii) NBPT plus nitrification inhibitor dicyandiamide, and (iii) nitrification inhibitor nitrapyrin (Nitrapyrin), as well as untreated UAN and urea, and polymer-coated urea (PCU). All fertilizers were applied by banding 50% at planting and 50% in-crop in early-spring, except PCU, where PCU was applied at planting and urea was applied in early-spring. Nitrous oxide (N2O) emissions and methane (CH4) uptake were measured at one rain-fed site from 2014 to 2017. NBPT increased grain yield by 1.2%–14% and 2.8%–4% under irrigated and rain-fed environments, respectively, relative to all the other N sources except untreated urea in the rain-fed environment. Total N uptake with NBPT was between 0% and 12% higher than the other N sources across irrigated and rain-fed environments. The results suggested that both grain yield and N use efficiency were optimized when UAN contained a urease inhibitor. All liquid enhanced efficiency fertilizers produced grain protein content greater than 11%, except Nitrapyrin under irrigated environments. Data from three site-years indicated that greenhouse gas emissions were unaffected by N source under rain-fed conditions. Liquid UAN with a urease inhibitor may have the most potential to optimize winter wheat production and N use efficiency in the Canadian Prairies.

Cover crops may improve soil health and increase soil carbon sequestration, thus contributing to both the adaptation to and mitigation of climate change. Despite these potential benefits, there currently lacks a global synthesis of the impacts of cover crops on soil organic carbon (SOC) fractions. We conducted a global meta-analysis of 93 peer-reviewed studies to quantify the effect of cover crops on changes in SOC fractions and the influence of environmental and management factors. Compared to bare soil management, cover crops increased SOC by 12% and increased seven SOC fractions, including microbial biomass carbon (MBC) by 33%, dissolved organic carbon (DOC) by 18%, particulate organic carbon (POC) by 15%, light-fraction organic carbon (LFOC) by 14%, permanganate oxidizable carbon (POXC) by 13%, short-term mineralizable carbon (SMC) by 10%, and mineral-associated organic carbon (MAOC) by 7%. The effect size of SOC was positively correlated with the effect sizes of MBC, POC, LFOC, and MAOC, but negatively correlated with the effect size of DOC. Soil taxonomic order and experimental duration were key factors affecting the beneficial effect of cover crops on the SOC fractions. Greater increases in SOC fractions due to cover crops were found in Entisols and Ultisols in comparison with other soil orders. The effect size of MAOC increased with experimental duration. Our study suggests that cover crops can significantly increase various SOC fractions, which likely serves as a building block for SOC sequestration and improvement of many aspects of soil health.

The microbial fermentation of plant feed by ruminants produces enteric methane (CH4), a potent greenhouse gas. Supplementing ruminant diets with an experimental methane inhibitor, 3-nitrooxypropanol (3-NOP), has been shown to decrease enteric CH4 production, but the effect of manure from these cattle on the soil microbiome has not been studied. In 2017 and 2018, we examined the effects of stockpiled manure and composted manure from cattle fed 3-NOP supplement alone or in combination with monensin (an ionophore) on soil permanganate-oxidizable C, microbial biomass C (MBC), the composition and diversity of prokaryotic and fungal commu-nities, and the activities of beta-glucosidase (C cycling), N-acetyl-beta-glucosaminidase (C and N cycling), acid and alkaline phosphomonoesterases (P cycling), and arylsuphatase (S cycling) in a forage cropping system. Stock -piled or composted manure from cattle fed 3-NOP increased MBC in 2017, fungal alpha-diversity in 2018 and the relative abundance of Actinobacteriota, but it decreased the relative abundances of Acidobacteriota and Basidio-mycota, relative to stockpiled or composted manure from cattle that were not fed 3-NOP. In 2017, relative to the conventional stockpiled manure, 3-NOP in stockpiled manure increased the activities of N-acetyl-beta-glucosami-nidase and acid phosphomonoesterase, but these effects were not observed for composted manure. Monensin, when used in combination with 3-NOP, did not affect any of the soil parameters measured in this study. The core microbiome found in 90 % of the soil samples included the bacterial and fungal genera Vicinamibacteraceae and Solicoccozyma, respectively. Therefore, 3-NOP manure or compost altered the composition of the soil micro-biome, and the 3-NOP in stockpiled manure increased the potential activities of enzymes involved in C-and-N and P cycling in the first year of the study, and fungal alpha-diversity in the second year, but no negative or persistent effects of 3-NOP on enzyme activities were observed.

To evaluate how enhanced efficiency liquid nitrogen (N) fertilizers affect winter wheat ( Triticum aestivum L.) production under irrigated and rain-fed environments, experiments were conducted at two irrigated and five rain-fed sites across the Canadian Prairies from 2013 to 2018 (22 site-years). The N fertilizers included urea ammonium nitrate (UAN) treated with ( i) urease inhibitor N-(n-butyl) thiophosphoric triamide (NBPT), ( ii) NBPT plus nitrification inhibitor dicyandiamide, and ( iii) nitrification inhibitor nitrapyrin (Nitrapyrin), as well as untreated UAN and urea, and polymer-coated urea (PCU). All fertilizers were applied by banding 50% at planting and 50% in-crop in early-spring, except PCU, where PCU was applied at planting and urea was applied in early-spring. Nitrous oxide (N2O) emissions and methane (CH4) uptake were measured at one rain-fed site from 2014 to 2017. NBPT increased grain yield by 1.2%–14% and 2.8%–4% under irrigated and rain-fed environments, respectively, relative to all the other N sources except untreated urea in the rain-fed environment. Total N uptake with NBPT was between 0% and 12% higher than the other N sources across irrigated and rain-fed environments. The results suggested that both grain yield and N use efficiency were optimized when UAN contained a urease inhibitor. All liquid enhanced efficiency fertilizers produced grain protein content greater than 11%, except Nitrapyrin under irrigated environments. Data from three site-years indicated that greenhouse gas emissions were unaffected by N source under rain-fed conditions. Liquid UAN with a urease inhibitor may have the most potential to optimize winter wheat production and N use efficiency in the Canadian Prairies.

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.

Manure can be a source of antibiotic resistance genes (ARGs) that enter the soil. However, previous studies assessing ARG persistence in soil have generally lacked continuity over sampling times, consistency of location, and assessing the impact of discontinuing manure application. We evaluated both short- and long-term ARG accumulation dynamics in soil with a 40-year known history of manure use. Manure application caused a greater abundance of tetracycline, macrolide, and sulfonamide ARGs in the soil. There was an initial spike in ARG abundance resulting from manure bacteria harboring ARGs being introduced to soil, followed by resident soil bacteria out-competing them, which led to ARG dissipation within a year. However, over four decades, annual manure application caused linear or exponential ARG accumulation, and bacteria associated with ARGs differed compared to those in the short term. Eleven years after discontinuing manure application, most soil ARG levels declined but remained elevated. We systematically explored the historical accumulation of ARGs in manured soil, and provide insight into factors that affect their persistence.

In orchard systems, organic amendments and cover crops may enhance soil organic carbon (SOC) and total nitrogen (STN) stocks, but on a global scale a comprehensive understanding of these practices is needed. This study reports a worldwide meta-analysis of 131 peer-reviewed publications, to quantify potential SOC and STN accumulation in orchard soils induced by organic fertilization and cover cropping. Annual gains of 3.73 Mg C/ha and 0.38 Mg N/ha were realized with the introduction of organic fertilizer, while cover crop management led to annual increases of 2.00 Mg C/ha and 0.20 Mg N/ha. The SOC and STN accumulation rates depended mostly on climatic conditions and initial SOC and STN content. The SOC and STN accumulated fastest during the first three years of cover crop implementation, at 2.98 Mg C/ha/yr and 0.25 Mg N/ha/yr and declined thereafter. Organic fertilization caused significantly more annual SOC and STN accumulation at higher (400–800 mm) than lower (<400 mm) rainfall levels. When cover cropping for more than five years, SOC accumulated the fastest with <800 mm of mean annual rainfall. Organic fertilization led to faster SOC accumulation with mean annual temperature between 15 and 20 °C than >20 °C. Organic amendments led to the slowest SOC accumulation rate when the initial SOC concentration was <10 g C/kg. This study provides policy makers and orchard managers science-based evidence to help guide adaptive management practices that build SOC stocks, improve soil conditions and enhance resilience of orchard systems to climate change.

Predicting the soil-available nitrogen (N) to grain corn over a growing season in humid temperate regions is the key for improving fertilizer N recommendations. The objective of this study was to evaluate a suite of soil-N tests to predict soil N availability to grain corn over two growing seasons at 13 individual sites with long-term history of synthetic N fertilization in Ontario, Canada (13 site-years). At each site, fertilizer N was applied at various rates (0–224 kg N·ha−1) to determine the crop response to N fertilizer, relative yield (RY), and the most economic rate of N (MERN). Across the entire dataset, water-extractable mineral N (WEMN) was the only soil test that strongly correlated to both RY (r = 0.74**) and MERN (r = −0.56*) indicating that in grain corn fields with long-term history of N fertilization, mineral forms of N in soil solution can be used for fertilizer N recommendations in southern and eastern Ontario. We also provide evidence that grouping soils based on clay content could further refine fertilizer-N recommendations for grain corn in Ontario. A multi-year validation of the WEMN test with more field sites and development of a fertilizer recommendation table for this soil test are recommended.

Soil salinization is a widespread problem affecting global food production. Phytoremediation is emerging as a viable and cost-effective technology to reclaim salt-affected soil. However, its efficiency is not clear due to the uncertainty of plant responses in saline soils. The main objective of this paper is to propose a phytoremediation dynamic model (PDM) for salt-affected soil within the process-based biogeochemical denitrificationdecomposition (DNDC) model. The PDM represents two salinity processes of phytoremediation: plant salt uptake and salt-affected biomass growth. The salt-soil-plant interaction is simulated as a coupled mass balance equation of water and salt plant uptake. The salt extraction ability by plant is a combination of salt uptake efficiency (F) and transpiration rate. For water filled pore space (WFPS), the statistical measures RMSE, MAE, and R-2 during the calibration period are 2.57, 2.14, and 0.49, and they are 2.67, 2.34, and 0.56 during the validation period, respectively. For soil salinity, RMSE, MAE, and R-2 during the calibration period are 0.02, 0.02, and 0.92, and 0.06, 0.04, and 0.68 during the validation period, respectively, which are reasonably good for further scenario analysis. Over the four years, cumulative salt uptake varied based on weather conditions. At the optimal salt uptake efficiency (F = 20), cumulative salt uptake from soil was 16-90% for alfalfa, 11-70% for barley, and 10-80% for spring wheat. While at the lowest salt uptake efficiency (F = 40), cumulative salt uptake was nearly zero for all crops. Although barley has the highest peak transpiration flux, alfalfa and spring wheat have greater cumulative salt uptake because their peak transpiration fluxes occurred more frequently than in barley. For salt tolerant crops biomass growth depends on their threshold soil salinity which determines their ability to take up salt without affecting biomass growth. In order to phytoremediate salt-affected soil, salt-tolerant crops having longer duration of crop physiological stages should be used, but their phytoremediation effectiveness will depend on weather conditions and the soil environment.

Tree crops are mainly planted on sloped farmland, which can lead to soil erosion caused by runoff. As an important tree crop management strategy, ground cover management has been effective in controlling runoff generation and soil loss. However, a global overview is needed to comprehensively quantify the effectiveness of ground cover on water and soil conservation. This study aims to conduct a worldwide meta-analysis of 85 peer-reviewed publications from Web of Science and China National Knowledge Infrastructure (CNKI) databases, to quantify the effectiveness of ground cover in reducing runoff, soil and nutrient losses. Overall, ground cover management significantly reduced runoff, soil loss, and nitrogen and phosphorus losses in runoff by 48.5%, 70.5%, and 53.4% and 56.9%, respectively. The magnitude of the effect of ground cover management mostly depended on ground cover types, land slope and climatic conditions. Cover cropping showed more efficiency in reducing runoff, soil and nutrient losses than mulch management. Legume cover crops were less effective than non-legumes, which was mainly attributed to the greater vegetation coverage of the perennial non-legume grasses than the annual legumes. Ground cover showed the most capacity to conserve water and soil at slopes between 10 and 15 degrees, with the tendency to lose effectiveness when field slopes were greater than 15 degrees. When pooling data according to different climatic conditions, the reduction of runoff, soil and nutrient losses were highest when mean annual precipitation and temperature were above 800 mm and 20 degrees C, respectively. This study can serve as a scientific basis for policy makers and tree crop managers in controlling soil erosion and land degradation based on ground cover type, physical topography and the climate where the agroecosystem is located.

Supplementing beef cattle with 3-nitrooxypropanol (3-NOP) decreases enteric methane production, but it is unknown if fertilizing soil with 3-NOP manure influences soil health. We measured soil health indicators 2 yr after manure application to a bromegrass (Bromus L.) and alfalfa (Medicago sativa L.) mixed crop. Treatments were: composted conventional manure (without supplements); stockpiled conventional manure; composted manure from cattle supplemented with 3-NOP; stockpiled 3-NOP manure; composted manure from cattle supplemented with 3-NOP and monensin (3-NOP+Mon), a supplement that improves digestion; stockpiled 3-NOP+Mon manure; inorganic fertilizer (150 kg N ha(-1) and 50 kg P ha(-1)); and an unamended control. Select chemical (K+, Mg2+, Mn+, Zn+, pH, and Olsen-P), biological (soil organic matter, active C, respiration, and extractable protein), physical (wet aggregate stability, bulk density, total porosity, and macro-, meso-, and micro-porosity), and hydraulic (saturation, field capacity, wilting point, water holding capacity, and hydraulic conductivity) variables were measured. The inclusion of monensin decreased soil Zn+ concentrations by 70% in stockpiled 3-NOP+Mon compared with stockpiled conventional manure. Active C and protein in composted conventional manure were 37 and 92% higher compared with stockpiled manure, respectively, but did not vary between 3-NOP treatments. 3-Nitrooxypropanol did not significantly alter other soil health indicators. Our results suggest that composted and stockpiled 3-NOP manure can be used as a nutrient source for forage crops without requiring changes to current manure management because it has minimal influence on soil health.

Grazing is one of the most widespread grassland management strategies. However, the effects of over six decades of different grazing intensities on soil bacterial community composition in the foothills of the Rocky Mountains are uncertain. We analyzed the bacterial community composition in soil samples collected in both summer and fall, 64 years after a long-term grazing intensity study was initiated in 1949. Grazing intensity treatments were (i) 0 animal-unit months (AUM) ha−1, (ii) 2.4 AUM ha−1 and (iii) 4.8 AUM ha−1, which represented the control, moderate and heavy grazing intensities, respectively. The evenness and diversity indices decreased with heavy grazing intensity relative to the other treatments in both summer and fall. In summer and fall, heavy grazing significantly shifted the bacterial community composition compared to the other treatments. Heavy grazing intensity significantly decreased the relative abundances of Bacteroidetes, Chlorobi, Nitrospirae and Proteobacteria, but significantly increased the relative abundance of Actinobacteria. Principal Coordinate Analyses revealed that available nitrogen, moisture content, total nitrogen and organic carbon were the primary environmental factors affecting the soil bacterial community composition. This study suggests that the effects of grazing on soil bacterial community composition are largely dependent on changes in soil physicochemical properties induced by the intensity of grazing over periods of six decades.

Soil salinity restricts plant growth, affects soil water balance and nitrous oxide (N2O) fluxes and can contaminate surface and groundwater. In this study, the Denitrification Decomposition (DNDC) model was modified to couple salt and water balance equations (SALT-DNDC) to investigate the effect of salinity on water balance and N2O fluxes. The model was examined against four growing seasons (2008-11) of observed data from Lethbridge, Alberta, Canada. Then, the model was used to simulate water filled pore space (WFPS), salt concentration and the N2O flux from agricultural soils. The results show that the effects of salinity on WFPS vary in different soil layers. Within shallow soil layers (<20 cm from soil surface) the salt concentration does not affect the average WFPS when initial salt concentrations range from 5 to 20 dS/m. However, in deeper soil layers (>20 cm from soil surface), when the initial salt concentration ranges from 5 to 20 dS/m it could indirectly affect the average WFPS due to changes of osmotic potential and transpiration. When AW is greater than 40%, the average growing season N2O emissions increase to a range of 0.6-1.0 g-N/ha/d at initial salt concentrations (5-20 dS/m) from a range of 0.5-0.7 g-N/ha/d when the salt concentrations is 0 dS/m. The newly developed SALT-DNDC model provides a unique tool to help investigate interactive effects among salt, soil, water, vegetation, and weather conditions on N2O fluxes.

The investigative material 3-nitrooxypropanol (3-NOP) can reduce enteric methane emissions from beef cattle. North American beef cattle are often supplemented the drug monensin to improve feed digestibility. Residual and confounding effects of these additives on manure greenhouse gas (GHG) emissions are unknown. This research tested whether manure carbon and nitrogen, and GHG and ammonia emissions, differed from cattle fed a typical finishing diet and 3-NOP [125–200 mg kg −1 dry matter (DM) feed], or both 3-NOP (125–200 mg kg −1 DM) and monensin (33 mg kg −1 DM) together, compared to a control (no supplements) when manure was stockpiled or composted for 202 days. Consistent with other studies, cumulative GHGs (except nitrous oxide) and ammonia emissions were higher from composted compared to stockpiled manure (all P < 0.01). Dry matter, total carbon and total nitrogen mass balance estimates, and cumulative GHG and ammonia emissions, from stored manure were not affected by 3-NOP or monensin. During the current experiment, supplementing beef cattle with 3-NOP did not significantly affect manure GHG or NH 3 emissions during storage under the tested management conditions, suggesting supplementing cattle with 3-NOP does not have residual effects on manure decomposition as estimated using total carbon and nitrogen losses and GHG emissions.

Cultivating native rangeland can have detrimental effects on soil carbon and nitrogen storage. Understanding how vegetation and soil recover after returning marginal cultivated land to its native state is important since soil plays a key role not only in food production but also in regulating global climate change. Soil samples were taken from two sites, a mixedgrass and a dry mixedgrass prairie, which have different climates and plant species composition. Each study site included one undisturbed native plot (CK) and two cultivated treatments that were abandoned in 2008 after being cultivated for more than ten years prior to this study, one with continuous wheat (Triticwn aestivurn L.) and the other with wheat-fallow rotations. Soil organic carbon (SOC), total nitrogen (TN), and labile organic fraction content were measured in 2016, while plant coverage and species diversity were investigated in 2017. In both study sites, grass and sedge coverage in the previously cultivated treatments were lower than, with shrub and forb coverage similar to, the CK. The highest invasive species coverage appeared in the previously cultivated treatments. Species richness was higher with CK in the mixedgrass prairie but no differences were found in the more arid dry mixedgrass prairie. No differences were found among all treatments for species evenness, Simpson's index and Shannon Wiener index. On average, in the 0-15 cm depth, SOC and TN contents with the previous cultivated treatments were still 20% and 16% lower than CK, respectively, whereas in the 15-30 cm depth, SOC and TN contents did not differ among all treatments except for SOC content in the mixedgrass prairie. Relative to CK, previously cultivated treatments had similar active carbon (AC), microbial respiration-carbon and NH4+ -N contents but the mixedgrass prairie had lower water extractable-organic carbon and water extractable-nitrogen. In contrast, in the dry mixedgrass prairie all labile organic fraction contents, except for AC, were the same among all treatments. Negative relationships were found between plant diversity and surface soil carbon and nitrogen storage. Our results indicate that for short-term disturbed rangeland, 9 years is likely sufficient for the recovery of soil labile organic fractions and plant diversity but a longer time will be needed for the recovery of SOC and TN.

Long-term manure application can build soil carbon and nutrient stocks and enhance enzyme activity, but its legacy on enzyme activity after discontinued application is unclear. We quantified soil microbial biomass carbon (MBC) and potential enzyme activities in fall, spring and summer in response to long-term manure application and its discontinuation under irrigated and rain-fed conditions. Relative to the non-amended control, 43 years of annual manure applications increased MBC by 38% and 33%, and beta-glucosidase, beta-N- acetyl-glucosaminidase (NAGase) and acid phosphomonoesterase activities by 35% and 33%, 137% and 135%, and 67% and 90%, in bulk and soybean rhizosphere soil, respectively, while arylsulphatase activity only increased in soybean rhizosphere by 13%. Fertilizer N had no effects on MBC or most enzyme activities, which were lowest in fall. In bulk and soybean rhizosphere soil, irrigation increased MBC, and NAGase and arylsulphatase activities by 17-33%, 19-54% and 39-57%, respectively, compared to rain-fed conditions, but beta-glucosidase and acid phosphomonoesterase activities increased by 25 and 12%, respectively, only in soybean rhizosphere. Legacy effects of manure applied 13 years previously were observed for MBC and all enzyme activities in bulk and soybean rhizosphere soil except MBC in bulk soil and acid phosphomonoesterase in soybean rhizosphere. Legacy effects of manure applied 29 years previously were observed for NAGase and arylsulphatase activities in bulk soil, and NAGase in soybean rhizosphere. Manure legacy effects on enzyme activities decreased with the number of years without manure, following quadratic patterns, and the effects lasted longer than those on MBC.