Alfalfa-grass mixtures reduce greenhouse gas emissions and net global warming potential while maintaining yield advantages over monocultures

Improving forage productivity with lower greenhouse gas (GHG) emissions from limited grassland has been a hotspot of interest in global agricultural production. In this study, we analyzed the effects of grasses (tall fescue, smooth bromegrass), legume (alfalfa), and alfalfa-grass (alfalfa + smooth bromegrass and alfalfa + tall fescue) mixtures on GHG emissions, net global warming potential (Net GWP), yield-based greenhouse gas intensity (GHGI), soil chemical properties and forage productivity in cultivated grassland in northwest China during 2020-2021. Our results demonstrated that alfalfa-grass mixtures significantly improved forage productivity. The highest total dry matter yield (DMY) during 2020 and 2021 was obtained from alfalfa-tall fescue (11,311 and 13,338 kg ha^-1) and alfalfa-smooth bromegrass mixtures (10,781 and 12,467 kg ha^-1). The annual cumulative GHG emissions from mixtures were lower than alfalfa monoculture. Alfalfa-grass mixtures significantly reduced GHGI compared with the grass or alfalfa monocultures. Furthermore, results indicated that grass, alfalfa and alfalfa-grass mixtures differentially affected soil chemical properties. Lower soil pH and C/N ratio were recorded in alfalfa monoculture. Alfalfa and mixtures increased soil organic carbon (SOC) and soil total nitrogen (STN) contents. Importantly, alfalfa-grass mixtures are necessary for improving forage productivity and mitigating the GHG emissions in this region. In conclusion, the alfalfa-tall fescue mixture lowered net GWP and GHGI in cultivated grassland while maintaining high forage productivity. These advanced agricultural practices could contribute to the development of climate-sustainable grassland production in China.

A new model of two-sown regime for oat forage production in an alpine region of northern China

Demand for high forage production and quality has been increased markedly by development of animal husbandry in China. The lack of efficient planting regimes and key technologies greatly limits production of high-quality forage. Oat has become an important forage in animal husbandry in China due to its high nutritional value and forage yield as well as its great adaptation to harsh environment. To maximize oat forage production in an alpine region, we developed a new model of oat forage production known as two-sown regime, i.e., the first spring-sown and the second summer-sown, during a single growing season in an alpine region of Hulun Buir, Inner Mongolia Autonomous Region, China, using two early-matured oat species, Avena sativa (cv. Qinghai444, winner oat cultivar) and A. nuda (cv. Huazao2, spring oat cultivar). The key technologies and the underlying agronomic mechanisms were investigated across three experimental years of 2017-2019. The main results were as follows: (1) dry weight yield, crude protein yield, and relative feed value of forage in the two-sown regime were significantly increased by 53.6%, 48.9%, and 70.6% relative to traditional one-sown regime across the 3 years, respectively; (2) forage production was mainly achieved by an increase in plant height at the first spring-sown; and (3) forage yield resulted mainly from an increase in tiller density by increasing seeding rate under no-tillage treatment in the second summer-sown. The key technologies of the two-sown regime were the first spring-sown at the soil thawing depth 10-13 cm, followed by the second summer-sown with increasing seeding rate under no-tillage treatment. These findings highlight that the two-sown regime of oat forage can be widely used as an effective planting regime to maximize forage production in large alpine regions of northern China as well as in regions with similar climates.

Evaluating economic and ecological management to determine the economic size of pastoral units for different climatic zones in the northeast of Iran

Stocking rate and rangeland area are key variables to provide the livelihood of herders in different climatic zones. To evaluate the economic and ecological management of pastoral units, this study aims to determine the optimal economic size of pastoral units for livestock grazing use considering the ecological capacity of semi-arid rangelands in different climatic scenarios. Therefore, 12 pastoral units (an area of 47,355 ha) were selected in two climatic zones (summer and winter rangelands) in the Kalat region of Razavi Khorasan Province, Iran. By measuring forage production, carrying capacity was calculated. Based on the results, the costs of traditional livestock management in winter rangelands are higher than those of summer rangelands. Moreover, the current size of the assigned rangeland, especially the summer rangeland, is lower than that of the economic justification. The results emphasize that rangeland-based livestock husbandry cannot create a good livelihood for herders in the region, and it is necessary to pay special attention to other services and aspects, despite the existing ecological and socio-economic complexities. In this regard, providing multi-purpose rangeland use and useable technologies to better manage these areas is necessary to increase per capita household income and reduce the stocking rate in the region's rangelands. Ultimately, both increasing the level of available rangelands and reducing costs by applying new technology are required, as is the economic consideration of pastoral units by using rangelands for multiple purposes.

Microclimate of grass canopies and biomass accumulation are influenced by the use of caged exclosures in grazing research

Exclosure cages are often used for estimating biomass accumulation on continuously stocked pastures in grazing experiments. The microclimate inside the cages may affect the estimates of biomass accumulation, but this has not been previously identified or quantified. We evaluated how the exclusion from grazing for 21 days in Mulato II brachiariagrass (Brachiaria brizantha × Brachiaria decumbens × Brachiaria ruziziensis) pastures affected canopy air temperature (T) and relative humidity (RH) and how this related to biomass accumulation. We also evaluated the effect of the exclosure cage on wind speed (WS) and incoming solar radiation (SR), and how these impacted evapotranspiration (ET) and estimates of biomass accumulation on grazed canopies maintained at 20- and 30-cm height under continuous stocking. Regardless of canopy height, changes in canopy structure during the exclusion period up to 21 days did not affect T and RH (averages of 24.3 °C and 88.7%, respectively), indicating that the air circulation was not affected by the exclusion. The cage structure reduced SR by 5%, although there were times during clear days when SR was slightly greater inside the cage than outside. The cage also reduced WS by 4.4%. Smaller SR and WS resulted in less ET inside the cages than outside, although with close values (2.9 vs. 3.0 mm day^-1; P = 0.0494). The biomass accumulation rate was greater inside than outside the cages for both canopy heights. This overestimation would be 5.8 and 9.7% greater if the structure of the cage did not reduce the SR, WS, and ET.

Warming reduces the production of a major annual forage crop on the Tibetan Plateau

Climate warming has been proposed to increase primary production of natural grasslands in cold regions. However, how climate warming affects the production of artificial pastures in cold regions remains unknown. To address this question, we used open-top chambers to simulate warming in a major artificial pasture (forage oat) on the cold Tibetan Plateau for three consecutive years. Surprisingly, climate warming decreased aboveground and belowground biomass production by 23.1%-44.8% and 35.0%-46.5%, respectively, without a significant impact on their ratio. The adverse effects on biomass production could be attributed to the adverse effects of high-temperatures on leaf photosynthesis through increases in water vapor pressure deficit (by 0.05-0.10 kPa), damages to the leaf oxidant system, as indicated by a 46.6% increase in leaf malondialdehyde content, as well as reductions in growth duration (by 4.7-6.7 days). The adverse effects were also related to exacerbated phosphorus limitation, as indicated by decreases in soil available phosphorus and plant phosphorus concentrations by 31.9%-40.7% and 14.3%-49.4%, respectively, and increases in the plant nitrogen: phosphorus ratio by 19.2%-108.3%. The decrease in soil available phosphorus concentration could be attributed to reductions in soil phosphatase activities (by 9.6%-18.5%). The findings of this study suggest an urgent need to advance agronomic techniques and cultivate more resilient forage genotypes to meet the increasing demand of forage for feeding livestock and to reduce grazing damage to natural grasslands on the warming-sensitive Tibetan Plateau.

Adaptation strategies of forage soybeans cultivated on acidic soils under cool climate to produce high quality forage

Boreal soils tend to be podzols characterized by acidic pH, which can further limit forage crop growth and production. It is unclear, how forage soybeans adopt to produce forage with high nutritional quality when cultivated on podzols in boreal climate. To answer this question, we cultivated forage soybeans on agricultural podzols at 3 farm sites with varied soil pH (6.8, 6.0 or 5.1), and assessed the root membrane lipidome remodeling response to such climatic conditions. Contrary to our expectations, significantly lower biomass was observed at pH 6.8 compared to 6.0 and 5.1. However, surprisingly the plants produced similar forage quality at 6.8 and 5.1 pH. Three major lipid classes including phospholipids, glycolipids and phytosterols were observed in roots irrespective of soil pH. Phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidic acid (PA), and acylated glucosyl betasitosterol ester (AGlcSiE) accounted for 95% of the root lipidome, and expressed significant changes in response to cultivation across the three soil pH levels. These lipids were also observed to have strong correlations with forage production, and forage quality. Therefore, soybean genotypes with higher abilities to remodel PC, PE, PA, and AGlcSiE could be better suited for producing higher quality forage in acid podzolic soils characteristics of boreal ecosystems.