Ruminating on soil carbon: Applying current understanding to inform grazing management.

Among options for atmospheric CO2 removal, sequestering soil organic carbon (SOC) via improved grazing management is a rare opportunity because it is scalable across millions of globally grazed acres, low cost, and has high technical potential. Decades of scientific research on grazing and SOC has failed to form a cohesive understanding of how grazing management affects SOC stocks and their distribution between particulate (POM) and mineral-associated organic matter (MAOM)-characterized by different formation and stabilization pathways-across different climatic contexts. As we increasingly look to grazing management for SOC sequestration on grazinglands to bolster our climate change mitigation efforts, we need a clear and collective understanding of grazing management's impact on pathways of SOC change to inform on-the-ground management decisions. We set out to review the effects of grazing management on SOC through a unified plant ecophysiology and soil biogeochemistry conceptual framework, where elements such as productivity, input quality, soil mineral capacity, and climate variables such as aridity co-govern SOC accumulation and distribution into POM and MAOM. To maximize applicability to grazingland managers, we discuss how common management levers that drive overall grazing pattern, including timing, intensity, duration, and frequency can be used to optimize mechanistic pathways of SOC sequestration. We discuss important research needs and measurement challenges, and highlight how our conceptual framework can inform more robust research with greater applicability for maximizing the use of grazing management to sequester SOC.

Leveraging Google Earth Engine for a More Effective Grassland Management: A Decision Support Application Perspective.

Grasslands cover a substantial portion of the earth's surface and agricultural land and is crucial for human well-being and livestock farming. Ranchers and grassland management authorities face challenges in effectively controlling herders' grazing behavior and grassland utilization due to underdeveloped infrastructure and poor communication in pastoral areas. Cloud-based grazing management and decision support systems (DSS) are needed to address this issue, promote sustainable grassland use, and preserve their ecosystem services. These systems should enable rapid and large-scale grassland growth and utilization monitoring, providing a basis for decision-making in managing grazing and grassland areas. In this context, this study contributes to the objectives of the EU LIFE IMAGINE project, aiming to develop a Web-GIS app for conserving and monitoring Umbria's grasslands and promoting more informed decisions for more sustainable livestock management. The app, called "Praterie" and developed in Google Earth Engine, utilizes historical Sentinel-2 satellite data and harmonic modeling of the EVI (Enhanced Vegetation Index) to estimate vegetation growth curves and maturity periods for the forthcoming vegetation cycle. The app is updated in quasi-real time and enables users to visualize estimates for the upcoming vegetation cycle, including the maximum greenness, the days remaining to the subsequent maturity period, the accuracy of the harmonic models, and the grassland greenness status in the previous 10 days. Even though future additional developments can improve the informative value of the Praterie app, this platform can contribute to optimizing livestock management and biodiversity conservation by providing timely and accurate data about grassland status and growth curves.

Effects of grazing platform stocking rate on productivity and profitability of pasture-based dairying in a fragmented farm scenario.

The area adjacent to the milking parlor, accessible for grazing by lactating dairy cows (i.e., the grazing platform [GP]), can be limited on fragmented pasture-based dairy farms. Such farms, with a moderate overall farm stocking rate, typically have a much higher stocking rate of dairy cows on the GP. This study quantified the effects of farm fragmentation on milk and herbage production and profitability in a whole-farm systems-scale study over 3 yr (2017-2019). Four systems, each with an overall farm stocking rate of 2.5 cows/ha but with different grazing platform stocking rates (GPSR), were examined. The proportions of the overall farm area within the GP were 100%, 83%, 71%, and 63% in each of the 4 systems, respectively. Hence, the 4 systems had a GPSR of 2.5, 3.0, 3.5, and 4.0 cows/ha. The GP was used for grazing and silage (ensiled herbage) production, and the non-GP portion of each GPSR system was used solely for silage production. Concentrate supplementation per cow was the same across all GPSR systems; approximately 10% of the annual feed budget. All systems were compact spring-calving with 24 cows per system. We discovered a lower proportion of grazed herbage in the diet with higher GPSR. All silage produced on the non-GP areas was required to support higher GPSR on each of the systems. Annual herbage production and milk production per cow were not different between GPSR systems, resulting in similar milk production per hectare of the overall system area. The economic implications of different GPSR on fragmented farms were modeled in 2 scenarios: (1) quantifying the cost associated with different levels of farm area fragmentation; (2) investigating the optimum GPSR on fragmented pasture-based dairy farms, depending on variable criteria. A greater level of farm fragmentation lowered the profitability of pasture-based dairy production. Costs of production increased with higher GPSR and longer distances between GP and non-GP areas. At a fixed GP area, it was most profitable to increase GPSR up to 4 cows/ha on the GP when milk price was high, land rental price was low, and shorter distance existed between GP and non-GP areas.

Field Evaluation of a Rising Plate Meter to Estimate Herbage Mass in Austrian Pastures.

Pasture management is an important topic for dairy farms with grazing systems. Herbage mass (HM) is a key measure, and estimations of HM content in pastures allow for informed decisions in pasture management. A common method of estimating the HM content in pastures requires manually collected grass samples, which are subjected to laboratory analysis to determine the dry matter (DM) content. However, in recent years, new methods have emerged that generate digital data and aim to expedite, facilitate and improve the measurement of HM. This study aimed to evaluate the accuracy of a rising plate meter (RPM) tool in a practical setting to estimate HM in Austrian pastures. With this study, we also attempted to answer whether the tool is ready for use by farmers with its default settings. This study was conducted on the teaching and research farm of the University of Veterinary Medicine in Vienna, Austria. Data were collected from May to October 2021 in five different pastures. To evaluate the accuracy of the RPM tool, grass samples were collected and dried in an oven to extract their DM and calculate the HM. The HM obtained from the grass samples was used as the gold standard for this study. In total, 3796 RPM measurements and 203 grass samples yielding 49 measurement points were used for the evaluation of the RPM tool. Despite the differences in pasture composition, the averaged HM from the RPM tool showed a strong correlation with the gold standard (R2 = 0.73, rp = 0.86, RMSE = 517.86, CV = 33.67%). However, the results may not be good enough to justify the use of the tool, because simulations in economic studies suggest that the error of prediction should be lower than 15%. Furthermore, in some pastures, the RPM obtained poor results, indicating an additional need for pasture-specific calibrations, which complicates the use of the RPM tool.

Shifts in sage-grouse arthropod food sources across grazing and environmental gradients in upland meadow communities.

Groundwater dependent systems are extremely important habitats for a wide variety of taxa in the Great Basin of North America. The impacts of grazing on these habitats cause shifts in resources and subsequent change in species composition. The Greater sage-grouse, a keystone species of Great Basin ecosystems, rear offspring in these areas during spring and summer months using forbs and arthropods. To examine the impact of grazing on arthropod abundance in these ecosystems, seven meadows, each made up of three unique vegetative communities, were grazed at three intensities across two years (2019-2020) and monitored for environmental variables and abundance of arthropods during peak sage-grouse utilization periods. Additionally, the relationship of field measurements and near-surface digital cameras (phenocams) was examined to better understand how remote sensing technologies can be used to monitor these insect abundance shifts on larger scales. Arthropod taxa abundance responded differently to grazing management and environmental variables. Coleoptera abundance during peak sage-grouse usage periods increased roughly 50% in some meadows with increased grazing intensity. For year-to-year environmental variability in precipitation, Lepidoptera abundance was 114% higher in the drier year, while Coleoptera was 39% lower. Near-surface cameras had varied success with predicting peak insect abundance levels. Lepidoptera and Coleoptera capture rates had strong correlations with phenological indices derived from phenocams, while Formicidae had much weaker relationships.

Diversifying livestock promotes multidiversity and multifunctionality in managed grasslands.

Increasing plant diversity can increase ecosystem functioning, stability, and services in both natural and managed grasslands, but the effects of herbivore diversity, and especially of livestock diversity, remain underexplored. Given that managed grazing is the most extensive land use worldwide, and that land managers can readily change livestock diversity, we experimentally tested how livestock diversification (sheep, cattle, or both) influenced multidiversity (the diversity of plants, insects, soil microbes, and nematodes) and ecosystem multifunctionality (including plant biomass production, plant leaf N and P, above-ground insect abundance, nutrient cycling, soil C stocks, water regulation, and plant-microbe symbiosis) in the world's largest remaining grassland. We also considered the potential dependence of ecosystem multifunctionality on multidiversity. We found that livestock diversification substantially increased ecosystem multifunctionality by increasing multidiversity. The link between multidiversity and ecosystem multifunctionality was always stronger than the link between single diversity components and functions. Our work provides insights into the importance of multitrophic diversity to maintain multifunctionality in managed ecosystems and suggests that diversifying livestock could promote both multidiversity and ecosystem multifunctionality in an increasingly managed world.

Access time to pasture under wet soil conditions: Effects on productivity and profitability of pasture-based dairying.

A long grazing season improves the profitability of pasture-based dairy production. It can entail grazing under wet soil conditions and the risk of damaging swards. Housing cows either temporarily or completely while soil moisture is high can avoid damaging swards. An experiment with 4 grazing systems was conducted over 3 yr (Sep. 1, 2013, to Aug. 31, 2016). The purpose was to evaluate whether soil moisture measurements are an effective decision support to assess the risk of treading damage and effects on pasture productivity and dairy cow performance during wet soil conditions. Access time to pasture between February and December of each grazing season was dependent on volumetric soil moisture content (VSMC, m3/m3) measured each morning: Control = cows were housed at VSMC >0.5 and otherwise allowed 22 h/d access to pasture; S<7 = cows were housed on days with VSMC >0.7 and otherwise allowed 22 h/d access to pasture; S7-6 = cows were housed at VSMC >0.7 and allowed 8 h/d access to pasture at VSMC between 0.7 and 0.6 and 22 h/d access at VSMC ≤0.6; S7-5 = cows were housed at VSMC >0.7 and allowed 8 h/d access to pasture at VSMC between 0.7 and 0.5 and 22 h/d access at VSMC ≤0.5. Cows with 8-h access per day received no other feeding when housed. All herds were compact spring-calving, with a mean calving date of Feb. 19. Mean stocking rate was 2.57 cows/ha. Measurements of VSMC provided an objective indicator for the risk of treading damage. Less time spent at pasture under wet soil conditions lowered treading damage but had no effect on annual pasture production (mean 14.8 t of organic matter/ha). Annual milk solids production per cow was lowest for the control herd (485 kg) and not different between the other systems (503 kg). Reducing treading damage to swards did not improve productivity or profitability of the grazing systems. Nevertheless, measuring soil moisture was a useful decision support for assessing the risk of treading damage when turning cows out to pasture.

Evaluation of a Binary Classification Approach to Detect Herbage Scarcity Based on Behavioral Responses of Grazing Dairy Cows.

In precision grazing, pasture allocation decisions are made continuously to ensure demand-based feed allowance and efficient grassland utilization. The aim of this study was to evaluate existing prediction models that determine feed scarcity based on changes in dairy cow behavior. During a practice-oriented experiment, two groups of 10 cows each grazed separate paddocks in half-days in six six-day grazing cycles. The allocated grazing areas provided 20% less feed than the total dry matter requirement of the animals for each entire grazing cycle. All cows were equipped with noseband sensors and pedometers to record their head, jaw, and leg activity. Eight behavioral variables were used to classify herbage sufficiency or scarcity using a generalized linear model and a random forest model. Both predictions were compared to two individual-animal and day-specific reference indicators for feed scarcity: reduced milk yields and rumen fill scores that undercut normal variation. The predictive performance of the models was low. The two behavioral variables "daily rumination chews" and "bite frequency" were confirmed as suitable predictors, the latter being particularly sensitive when new feed allocation is present in the grazing set-up within 24 h. Important aspects were identified to be considered if the modeling approach is to be followed up.

Living with exotic annual grasses in the sagebrush ecosystem.

Exotic annual grasses dominate millions of hectares and increase fire frequency in the sagebrush ecosystem of North America. This devastating invasion is so costly and challenging to revegetate with perennial vegetation that restoration efforts need to be prioritized and strategically implemented. Management needs to break the annual grass-fire cycle and prevent invasion of new areas, while research is needed to improve restoration success. Under current land management and climate regimes, extensive areas will remain annual grasslands, because of their expansiveness and the low probability of transition to perennial dominance. We propose referring to these communities as Intermountain West Annual Grasslands, recognizing that they are a stable state and require different management goals and objectives than perennial-dominated systems. We need to learn to live with annual grasslands, reducing their costs and increasing benefits derived from them, at the same time maintaining landscape-level plant diversity that could allow transition to perennial dominance under future scenarios. To accomplish this task, we propose a framework and research to improve our ability to live with exotic annual grasses in the sagebrush biome.

Seasonal variation in the response of arbuscular mycorrhizal fungi to grazing intensity.

Despite existing evidence of pronounced seasonality in arbuscular mycorrhizal (AM) fungal communities, little is known about the ecology of AM fungi in response to grazing intensity in different seasons. Here, we assessed AM fungal abundance, represented by soil hyphal length density (HLD), mycorrhizal root colonization intensity (MI), and arbuscule intensity (AI) throughout three seasons (spring, summer, autumn) in a farm-scale field experiment in typical, grazed steppe vegetation in northern China. Seven levels of field-manipulated, grazing intensities had been maintained for over 13 years within two topographies, flat and slope. We also measured soil nutrients and carbon content throughout the growing season to investigate whether seasonal variation in AM fungal abundance was related to seasonal shifts in soil resource availability along the grazing gradient. We further examined the association between AM fungal metrics in the different grazing treatments through the growing season. Our results showed a pronounced seasonal shift in HLD but there was no clear seasonality in MI and AI. HLD was significantly negatively related to grazing intensity over the course of the growing season from spring to autumn. However, MI and AI were related negatively to grazing intensity only in spring. In addition, differential responses of AM fungal abundance to grazing intensity at the two topographical sites were detected. No strong evidence was found for associations between AM fungal abundance and soil resource availability. Moreover, AM fungal internal and external abundance were correlated positively under the different grazing intensities throughout the growing season. Overall, our study suggests that external AM fungal structures in soil were more responsive to seasonal variation and grazing than internal structures in roots. The findings also suggest that early grazing may be detrimental to AM fungal root colonization of newly emerged plants.

Questionnaire survey on helminth control practices in horse farms in Ireland.

Knowledge regarding helminth control strategies and nematode infection of horses in Ireland is limited and only one study has been published recently. This present study was designed to investigate the current helminth control strategies followed by horse owners in Ireland. A questionnaire was formulated to collect data on general grazing, pasture management and deworming strategies including the use of fecal egg counts. Questionnaires were emailed to 700 members of the Irish Thoroughbred Breeders Association and Horse Sport Ireland. Only 78 questionnaires were returned. Respondents indicated that horses are grazed for 16-24 h day-1 during the summer and autumn (89% and 65%, respectively). Removing feces from the pasture was implemented by 37.6% of respondents. Few (22.2%) owners kept horses off pasture after worming. Overall, ivermectin and moxidectin were the most commonly administered anthelmintics in 2014 by 75% and 62% of respondents, respectively. Benzimidazole and pyrantel drugs were used by 53% and 35% of respondents, respectively. The majority of farms (81.4%) treated horses 4-5 times per year and 74.2% only estimated the weight of the horses visually. The findings of this study illustrates that many stud managers/owners do not follow best practice with regard to helminth control and more education is needed.

Carbon footprint of dairy goat production systems: A comparison of three contrasting grazing levels in the Sierra de Grazalema Natural Park (Southern Spain).

The main objective of this study was to analyze the carbon footprint (CF) of grazing dairy goat systems in a natural park according to their grazing level. A total of 16 representative grazing goat farms in southern Spain were selected and grouped into three farming systems: low productivity grazing farms (LPG), more intensified grazing farms (MIG) and high productivity grazing farms (HPG). Their CF was analyzed, including greenhouse gas emissions and soil C sequestration according to the farms' grazing level and milk productivity, taking into account different functional units (one kilogram of fat and protein corrected milk (FPCM) and one hectare) and milk correction. Results showed that all variables differed according to the milk correction applied as the values for cow's milk correction were 41% lower than for sheep's milk correction. Total emissions and contributions of soil carbon sequestration differed according to farming system group; LPG farms had higher total emissions than MIG and HPG farms, however total carbon sequestration was lower in the MIG farms than in the LPG and HPG farms. The CF values ranged from 2.36 to 1.76 kg CO2e kg-1 FPCM for sheep's milk correction and from 1.40 to 1.04 kg CO2e kg-1 FPCM for cow's milk correction. No differences were found between farming system groups in either of the two cases but when calculations took hectare of land as a functional unit, the contribution of MIG farms to the CF was 85% higher than LPG and HPG farms. Therefore it is important to take into account the functional unit used to calculate the CF by analyzing this indicator in a broader context, and including carbon sequestration by grazing livestock in the calculation. In order to reduce the CF of this type of system, it is advisable to make appropriate use of the natural resources and to reach an optimum level of milk productivity, high enough for pastoral livestock farming to be viable.

Assessing the feasibility of carbon payments and Payments for Ecosystem Services to reduce livestock grazing pressure on saltmarshes.

Saltmarshes provide important services including flood control, climate regulation, and provisioning services when grazed by livestock for agriculture and conservation purposes. Grazing diminishes aboveground carbon, creating a trade-off between these two services. Furthermore, saltmarshes are threatened by overgrazing. To provide saltmarsh protection and ensure the continuing delivery of ecosystem services, there is a need to incentivise land managers to stock environmentally sensible densities. We therefore investigated the possibility of agri-environmental schemes and Payments for Ecosystem Services (PES) to compensate for lost livestock revenue under reduced grazing regimes and provide carbon sequestration and other benefits. This is the first study to consider the benefits arising from a potential carbon market to saltmarshes, although similar schemes exist for peatland and woodland. We calculated the net economic benefit (costs of livestock production are removed from revenue) to farmers obtained from a hectare of grazed saltmarsh under low (0.3 Livestock Units per hectare per year), moderate (0.6), high (1.0) and very high (2.0) stocking densities accounting for livestock revenue, carbon benefits, and agri-environmental subsidies. We repeated the procedure considering additional benefits transferred from the literature in terms of provisioning, regulating and cultural ecosystem services provided by protected saltmarshes. The net benefits were assessed for a range of market carbon prices and social costs of carbon, e.g. the opportunity cost of carbon for society. Applying the model to Scottish saltmarshes we find that the current range of market prices could prompt transitions from high to moderate regimes in areas where livestock value is low, however break-even prices for transitions showed high spatial variability due to spatial variability in livestock values. In some areas of the West Highlands, the break-even carbon price is negative, indicating that the current agri-environmental schemes are able to more than compensate for the lost revenue accruing to farmers by a reduced grazing density. However, in other areas, such as the Outer Hebrides, the break-even carbon price is positive. Private PES schemes or increased public subsidies should then be provided to generate net benefits. It is reasonable to infer that a pure carbon market may have limited scope in incentivising consumers to buy carbon services, especially in areas with limited local number of buyers and corporates of small size. Under this circumstance, a premium carbon market offering bundled ecosystem services may help reduce grazing pressure across a larger number of Scottish saltmarshes, thereby providing globally important climate regulation services and at the same time protecting sensitive habitats.

Effect of feeding strategies and cropping systems on greenhouse gas emission from Wisconsin certified organic dairy farms.

Organic agriculture continues to expand in the United States, both in total hectares and market share. However, management practices used by dairy organic producers, and their resulting environmental impacts, vary across farms. This study used a partial life cycle assessment approach to estimate the effect of different feeding strategies and associated crop production on greenhouse gas emissions (GHG) from Wisconsin certified organic dairy farms. Field and livestock-driven emissions were calculated using 2 data sets. One was a 20-yr data set from the Wisconsin Integrated Cropping System Trial documenting management inputs, crop and pasture yields, and soil characteristics, used to estimate field-level emissions from land associated with feed production (row crop and pasture), including N2O and soil carbon sequestration. The other was a data set summarizing organic farm management in Wisconsin, which was used to estimate replacement heifer emission (CO2 equivalents), enteric methane (CH4), and manure management (N2O and CH4). Three combinations of corn grain (CG) and soybean (SB) as concentrate (all corn = 100% CG; baseline = 75% CG + 25% SB; half corn = 50% CG + 50% SB) were assigned to each of 4 representative management strategies as determined by survey data. Overall, GHG emissions associated with crop production was 1,297 ± 136 kg of CO2 equivalents/t of ECM without accounting for soil carbon changes (ΔSC), and GHG emission with ΔSC was 1,457 ± 111 kg of CO2 equivalents/t of ECM, with greater reliance on pasture resulting in less ΔSC. Higher levels of milk production were a major driver associated with reduction in GHG emission per metric tonne of ECM. Emissions per metric tonne of ECM increased with increasing proportion of SB in the ration; however, including SB in the crop rotation decreased N2O emission per metric tonne of ECM from cropland due to lower applications of organically approved N fertility inputs. More SB at the expense of CG in the ration reduced enteric CH4 emission per metric tonne of ECM (because of greater dietary fat content) but increased N2O emission per metric tonne of ECM from manure (because of greater N content). An increased reliance on pasture for feed at the expense of grain resulted in decreased in milk production, subsequently leading to substantially higher emissions per metric tonne of ECM.

Milk production and composition, nitrogen utilization, and grazing behavior of late-lactation dairy cows as affected by time of allocation of a fresh strip of pasture.

Eighty late-lactation dairy cows were used to examine the effects of allocating a new pasture strip of a sward based on ryegrass (Lolium perenne L.) in the morning (a.m.; ∼0730 h) or in the afternoon (p.m.; ∼1530 h) on milk production and composition, nitrogen (N) utilization, and grazing behavior. Cows grazed the same pasture strips for 24 h and were offered the same daily herbage allowance. Herbage composition differed among treatments; p.m. herbage had greater dry matter (DM; 22.7 vs. 19.9%), organic matter (OM; 89.5 vs. 88.9%), and water-soluble carbohydrate (10.9 vs. 7.6%) concentrations and lesser crude protein (20.5 vs. 22.2%) and neutral detergent fiber (48.8 vs. 50.4%) concentrations compared with a.m. herbage. Total fatty acids (FA), α-linolenic acid, and polyunsaturated FA (PUFA) were greater in a.m. herbage, whereas monounsaturated FA were greater in p.m. herbage. Estimates of herbage DM intake did not differ among treatments. Daily milk yields and milk fat and milk protein concentrations were similar among treatments, whereas milk fat (684 vs. 627 g/cow), milk protein (545 vs. 505 g/cow), and milk solids (milk fat + milk protein) yields (1,228 vs. 1,132 g/cow) tended to be greater for cows on p.m. herbage. Rumenic acid and total PUFA in milk were greater for cows on a.m. herbage, whereas oleic acid was greater for cows on p.m. herbage. Estimates of urinary N excretion (g/d) did not differ among treatments, but urinary N concentrations were greater for cows on a.m. herbage (5.85 vs. 5.36 g/L). Initial herbage mass (HM) available (kg of DM/ha) and instantaneous HM disappearance rates (kg of DM/ha and kg of DM/h) did not differ, but fractional disappearance rates (0.56 vs. 0.74 per hour for a.m. vs. p.m., respectively) differed. Under the current conditions, timing of pasture strip allocation altered the herbage nutrient supply to cows; allocating a fresh strip of pasture later in the day resulted in moderate increases in milk and milk solids yields in late-lactation dairy cows. Conversely, a greater concentration of precursor FA in a.m. herbage resulted in a greater concentration of beneficial FA in milk, compared with cows on p.m. herbage.

Potential of an outranking multi-criteria approach to support the participatory assessment of land management actions.

We evaluated the potential of an outranking Multi-Criteria Decision Analysis approach for assisting in the participatory assessment of dryland management actions implemented in the San Simon watershed, in southeastern Arizona, USA. We compared an outranking-facilitated assessment of actions with a simple and direct (baseline) ranking of the same actions by the participating stakeholders in terms of: 1) internal homogeneity of each assessment approach, (2) similarity of individual assessments between methods, and (3) effects of the use of implicit/explicit assessment criteria. The actions assessed combined various management approaches, including livestock management (rotation, resting), vegetation management (grass seeding, brush control), and hydraulic structures (dams, dykes). The outranking-facilitated assessment discriminated better between actions and reduced the variability of results between individual stakeholders as compared with the direct ranking of actions. In general, the two assessments significantly differed in the relative preference of the five management actions assessed, yet both assessments identified rotational grazing combined with vegetation management (grass seeding and brush control) as the most preferred management action in the study area. The comparative analysis revealed inconsistencies between the use of implicit and explicit assessment criteria. Our findings highlight the opportunities offered by outranking approaches to help capture, structure, and make explicit stakeholder perspectives in the framework of a participatory environmental assessment process, which may facilitate the understanding of the multiple preferences involved. The outranking integration process, which resembles a voting procedure, proved simple and transparent, with potential for contributing to stakeholder engagement and trust in participatory assessment.

Pasture BMP effectiveness using an HRU-based subarea approach in SWAT.

Many conservation programs have been established to motivate producers to adopt best management practices (BMP) to minimize pasture runoff and nutrient loads, but a process is needed to assess BMP effectiveness to help target implementation efforts. A study was conducted to develop and demonstrate a method to evaluate water-quality impacts and the effectiveness of two widely used BMPs on a livestock pasture: off-stream watering site and stream fencing. The Soil and Water Assessment Tool (SWAT) model was built for the Pottawatomie Creek Watershed in eastern Kansas, independently calibrated at the watershed outlet for streamflow and at a pasture site for nutrients and sediment runoff, and also employed to simulate pollutant loads in a synthetic pasture. The pasture was divided into several subareas including stream, riparian zone, and two grazing zones. Five scenarios applied to both a synthetic pasture and a whole watershed were simulated to assess various combinations of widely used pasture BMPs: (1) baseline conditions with an open stream access, (2) an off-stream watering site installed in individual subareas in the pasture, and (3) stream or riparian zone fencing with an off-stream watering site. Results indicated that pollutant loads increase with increasing stocking rates whereas off-stream watering site and/or stream fencing reduce time cattle spend in the stream and nutrient loads. These two BMPs lowered organic P and N loads by more than 59% and nitrate loads by 19%, but TSS and sediment-attached P loads remained practically unchanged. An effectiveness index (EI) quantified impacts from the various combinations of off-stream watering sites and fencing in all scenarios. Stream bank contribution to pollutant loads was not accounted in the methodology due to limitations of the SWAT model, but can be incorporated in the approach if an amount of bank soil loss is known for various stocking rates. The proposed methodology provides an adaptable framework for pasture BMP assessment and was utilized to represent a consistent, defensible process to quantify the effectiveness of BMP proposals in a BMP auction in eastern Kansas.

Incorporating a prediction of postgrazing herbage mass into a whole-farm model for pasture-based dairy systems.

The DairyNZ whole-farm model (WFM; DairyNZ, Hamilton, New Zealand) consists of a framework that links component models for animal, pastures, crops, and soils. The model was developed to assist with analysis and design of pasture-based farm systems. New (this work) and revised (e.g., cow, pasture, crops) component models can be added to the WFM, keeping the model flexible and up to date. Nevertheless, the WFM does not account for plant-animal relationships determining herbage-depletion dynamics. The user has to preset the maximum allowable level of herbage depletion [i.e., postgrazing herbage mass (residuals)] throughout the year. Because residuals have a direct effect on herbage regrowth, the WFM in its current form does not dynamically simulate the effect of grazing pressure on herbage depletion and consequent effect on herbage regrowth. The management of grazing pressure is a key component of pasture-based dairy systems. Thus, the main objective of the present work was to develop a new version of the WFM able to predict residuals, and thereby simulate related effects of grazing pressure dynamically at the farm scale. This objective was accomplished by incorporating a new component model into the WFM. This model represents plant-animal relationships, for example sward structure and herbage intake rate, and resulting level of herbage depletion. The sensitivity of the new version of the WFM was evaluated and then the new WFM was tested against an experimental data set previously used to evaluate the WFM and to illustrate the adequacy and improvement of the model development. Key outputs variables of the new version pertinent to this work (milk production, herbage dry matter intake, intake rate, harvesting efficiency, and residuals) responded acceptably to a range of input variables. The relative prediction errors for monthly and mean annual residual predictions were 20 and 5%, respectively. Monthly predictions of residuals had a line bias (1.5%), with a proportion of square root of mean square prediction error (RMSPE) due to random error of 97.5%. Predicted monthly herbage growth rates had a line bias of 2%, a proportion of RMSPE due to random error of 96%, and a concordance correlation coefficient of 0.87. Annual herbage production was predicted with an RMSPE of 531 (kg of herbage dry matter/ha per year), a line bias of 11%, a proportion of RMSPE due to random error of 80%, and relative prediction errors of 2%. Annual herbage dry matter intake per cow and hectare, both per year, were predicted with RMSPE, relative prediction error, and concordance correlation coefficient of 169 and 692kg of dry matter, 3 and 4%, and 0.91 and 0.87, respectively. These results indicate that predictions of the new WFM are relatively accurate and precise, with a conclusion that incorporating a plant-animal relationship model into the WFM allows for dynamic predictions of residuals and more realistic simulations of the effect of grazing pressure on herbage production and intake at the farm level without the intervention from the user.

Nutritional Quality and Socio-Ecological Benefits of Mare Milk Produced under Grazing Management.

This review discusses the scientific evidence that supports the nutritional value of mare milk and how its properties are essentially achieved when mares are managed under grazing conditions. Mare milk's similarity with the chemical composition of human milk makes this food and its derived products not only suitable for human consumption but also an interesting food regarding human health. The contribution of horse breeding under grazing management to other socio-ecological benefits generated by equine farms is also highlighted. Both the high added value of mare milk and the socio-ecological benefits derived from pasture-based systems could be explored to improve the performance of equine farms located in arid and semi-arid areas or in regions with moderately harsh environmental conditions as equids have a strong adaptation capacity.

Impact of time-lagging and time-preceding environmental variables on top layer soil moisture in semiarid grasslands.

Top soil moisture (SM) is an important medium connecting the exchange of matter and energy between the ground and the atmosphere. Previous studies of the relationship between SM and environmental factors, especially aerodynamics, have lacked analysis of the variability in the timing of effects. In this study, we analyzed how environmental factors affect SM, as well as soil moisture memory, by observing precipitation, radiation, and wind speed during the 2019 to 2021 growing seasons in grazing prohibited and grazed areas of a semiarid grassland. The results show that there is a clear threshold (7 mm) for the effect of precipitation on SM, that changes in SM across time scales were influenced by preceding precipitation and net radiation in addition to lagging vegetation greening characteristics (NDVI) and wind speed, and that the role of albedo was related to grazing management. The inhibitory effect of albedo on SM and the depletion of SM by NDVI were more pronounced in comparison to other meteorological factors. Wind speed, precipitation, and radiation directly or indirectly influenced SM duration, and these relationships varied with grazing management and annual variation. These results help to clarify the influence of environmental factors on SM, and provide insight for minimizing the degradation of grassland ecosystems in the process of climate change.