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Direct evidence-based approaches are vital to evaluating newly proposed theories on the persistence of soil organic carbon and establishing the contributions of abiotic and biotic controls. Our primary goal was to directly identify the mechanisms of organic carbon stabilization in native-state, free soil microaggregates without disrupting the aggregate microstructure using scanning transmission x-ray microscopy coupled with near edge x-ray absorption fine structure spectroscopy (STXM-NEXAFS). The influence of soil management practices on microaggregate associated-carbon was also assessed. Free, stable soil microaggregates were collected from a tropical agro-ecosystem in Cruz Alta, Brazil. The long-term experimental plots (>25 years) comparing two tillage systems: no-till and till with a complex crop rotation. Based on simultaneously collected multi-elemental associations and speciation, STXM-NEXAFS successfully provided submicron level information on organo-mineral associations. Simple organic carbon sources were found preserved within microaggregates; some still possessing original morphology, suggesting that their stabilization was not entirely governed by the substrate chemistry. Bulk analysis showed higher and younger organic carbon in microaggregates from no-till systems than tilled systems. These results provide direct submicron level evidence that the surrounding environment is involved in stabilizing organic carbon, thus favoring newly proposed concepts on the persistence of soil organic carbon.

The North American prairie covered about 3.6 million-km2 of the continent prior to European contact. Only 1-2% of the original prairie remains, but the soils that developed under these prairies are some of the most productive and fertile in the world, containing over 35% of the soil carbon in the continental United States. Cultivation may alter microbial diversity and composition, influencing the metabolism of carbon, nitrogen, and other elements. Here, we explored the structure and functional potential of the soil microbiome in paired cultivated-corn (at the time of sampling) and never-cultivated native prairie soils across a three-states transect (Wisconsin, Iowa, and Kansas) using metagenomic and 16S rRNA gene sequencing and lipid analysis. At the Wisconsin site, we also sampled adjacent restored prairie and switchgrass plots. We found that agricultural practices drove differences in community composition and diversity across the transect. Microbial biomass in prairie samples was twice that of cultivated soils, but alpha diversity was higher with cultivation. Metagenome analyses revealed denitrification and starch degradation genes were abundant across all soils, as were core genes involved in response to osmotic stress, resource transport, and environmental sensing. Together, these data indicate that cultivation shifted the microbiome in consistent ways across different regions of the prairie, but also suggest that many functions are resilient to changes caused by land management practices - perhaps reflecting adaptations to conditions common to tallgrass prairie soils in the region (e.g., soil type, parent material, development under grasses, temperature and rainfall patterns, and annual freeze-thaw cycles). These findings are important for understanding the long-term consequences of land management practices to prairie soil microbial communities and their genetic potential to carry out key functions.

Direct evidence-based approaches are vital in understanding the involvement of abiotic/biotic factors and evaluating the newly proposed theories on soil carbon (C) stabilization. Microaggregates (150–250 μm) collected from a corn system (>22 years; Kansas, USA), which had been under no-till with different nitrogen (N) treatments were analyzed (N treatments: manure/compost, urea, zero fertilizer). We studied C stabilization in free soil microaggregates (with preserved aggregate architecture), directly using scanning transmission X-ray microscopy coupled with near edge X-ray absorption fine structure (STXM-NEXAFS) spectroscopy. Submicron scale findings were complemented with bulk chemical analysis. The STXM-NEXAFS analysis revealed soil organic carbon (SOC) preservation inside nano- and micro-pores and organo–mineral association, various degrees of humification, and high molecular diversity. The presence of microbial-derived C was found in manure-/compost-added microaggregates highlighting the contribution of organic amendments in facilitating microbial diversity. The incidence of aragonite-like minerals suggested the biologically/chemically active nature of microaggregate cores. Bulk analysis of free microaggregates showed a higher concentration of SOC (6.5%), ammonium oxalate extractable Fe/Al/Si), and higher aliphaticity of humic acid in manure-/compost-added soils compared to inorganic fertilizer (3% SOC) and control (2.7% SOC) treatments. The co-existence of elements (calcium [Ca]/C, iron [Fe]/N, Fe/C, aluminum [Al]/C, and silicon [Si]/C) was partially supported by bulk chemical analysis that indicated a strong association between ammonium oxalate extractable Fe/Al/Si and SOC (R² = 0.63—0.77). Overall, our study provided direct/indirect evidence for the complex and interactive involvement of chemical, mineralogical, and biological mechanisms that may have been stimulated by the long-term addition of compost/manure in stabilizing SOC. [ABSTRACT FROM AUTHOR]

On‐farm research has emerged in recent years as a unique approach to involve farmers and other agricultural stakeholders as active participants in knowledge development and as an effective method of technology and innovation transfer across farms. This study assessed the perspective and knowledge of US farmers regarding on‐farm research via the implementation of a 24‐question survey distributed across most of the US Midwest and South‐Central regions. We found that farmers generally are willing to engage with universities to conduct on‐farm research and were 40% more likely to adopt practices supported by on‐farm research findings than research not conducted on‐farm. Notably, a shift toward conservation practices was made, with cover crops and no‐till at the forefront. Insights of this nature have implications for fostering collaborations, addressing constraints, and maximizing the impact of on‐farm research, offering guidance for sustainable agriculture progress in the United States and beyond. Results from this research survey could be used to initiate much‐needed policies to promote on‐farm research. Further, information on the benefits and drawbacks of on‐farm research could be used in the development of studies that benefit both farmers and researchers. Core Ideas: Farmers are likely to collaborate with universities to conduct on‐farm research.Farmers were 40% more likely to adopt practices supported by findings of on‐farm research compared to off‐farm research.The farmers' primary motivators for doing on‐farm research were productivity and profitability.The farmers' primary source of field information is universities.Results from this research survey can drive further policy and initiatives promoting on‐farm research. [ABSTRACT FROM AUTHOR]

The Central Great Plains Climate Education Partnership conducted focus groups throughout Kansas to gain a better understanding of farmer perceptions and attitudes towards climate change education. Results indicate concern about climatic changes, even if producers are unsure that "human caused climate change" is occurring. Participants indicated they would like access to information through Web-based programs that allow them to manipulate variables relevant to their area and situation. Participants prefer locally relevant information and identified Extension agents as trusted educators. The study provided an expanded understanding of agricultural producer perceptions that will be valuable to individuals or organizations providing climate education. [This research was supported by NSF-CCEP #1135395, Central Great Plains Climate Change Education Partnership.]