Biochar has significant potential for livestock microbiomes and crop agriculture regarding greenhouse gas emissions reduction. Therefore, a pilot study was designed to investigate the effect of biochar application on the surface of swine manure from an open lagoon and the associated microbial communities. Samples were collected from four different treatment groups: control (n = 4), coarse biochar (n = 4), fine biochar (n = 4), and ultra-fine biochar (n = 4). Additionally, aged manure in bulk was collected (n = 4) to assess alterations from the control group. The method of 16S rRNA amplicon sequencing along with microbial analyses was performed. Diversity was significantly different between aged manure in bulk samples and all treatment groups (Kruskal–Wallis; p < 0.05). Additionally, distinct community compositions were seen using both weighted and unweighted UniFrac distance matrices (PERMANOVA; p < 0.01). Differential abundance analysis revealed four distinct features within all treatment groups that were enriched (q < 0.001): Idiomarina spp., Geovibrio thiophilus, Parapusillimonas granuli, and an uncultured Gammaproteobacteria species. Similarly, Comamonas spp. and Brumimicrobium aurantiacum (q-value < 0.001) were significantly depleted by all the treatments. Stochastic and functional analyses revealed that biochar treatments were not deterministically altering assembly patterns, and functional redundancy was evident regardless of compositional shifts.

Soybean (Glycine max L. [Merr.]) nitrogen fixation is sensitive to soil drying and is an important target for improving soybean drought resilience. Transcriptional regulation of the nodule drought response and the influence of symbiotic rhizobia are not well understood. We measured whole-plant responses to mild and moderate soil moisture deficit (41% and 20% of field capacity) alongside the nodule transcriptome, including soybean and Bradyrhizobium diazoefficiens transcripts, in two soybean genotypes (‘Benning’ and PI 471938) that were previously found to have diverging nitrogen fixation drought responses. The transcriptomes of the two genotypes responded very similarly to soil moisture deficit, with only eight genes responding to soil moisture deficit differently between genotypes. Mild soil moisture deficit reduced stomatal conductance and increased stem and petiole ureide while altering transcript abundance of genes involved in nitrogen assimilation-related pathways in both plant genotypes and in the bacteroid. Gene regulatory network inference identified two B. diazoefficiens loci, BAC49768 and BAC47090, as major regulators in the whole-nodule transcriptome during soil moisture deficit. Several soybean network nodes were located within quantitative trait loci previously associated with relevant drought responses. This work revealed new soybean and rhizobia candidate genes with important roles in the soybean nodule drought response.

Climate variability and widespread synthetic agrochemical use have increased interest in biostimulants (BS) that enhance plant growth, stress tolerance, and yield by stimulating natural plant processes. A two-site field study, conducted under no-till and tilled systems, evaluated the effects of the foliar biostimulant “Source” on soybean growth and yield at three phosphorus (P) rates (0%, 50%, and 100% of soil test recommendations) because of its potential to replace phosphorus inputs. A complementary greenhouse study was conducted to evaluate the effect of the biostimulant on different soybean hybrids. Measured at various dates after planting (DAP), leaf relative water content (LRWC) and normalized difference vegetation index (NDVI) mostly showed insignificant responses to P treatments, but significant responses to BS. Grain yield increased significantly with individual BS and P applications in both tillage systems. Under no-till conditions, BS increased yield by 13.0% (3.05 vs. 2.70 Mg ha⁻¹), and P100 increased yield by 13.5% (3.0 vs. 2.65 Mg ha⁻¹). Under tilled conditions, BS and P100 increased yield by 19.6% (2.75 vs. 2.30 Mg ha⁻¹) and 19.2% (2.72 vs. 2.28 Mg ha⁻¹), respectively, compared with the control. Yield gains were primarily driven by increased pod density and grain number. Greenhouse experiments supported these trends, with BS-treated plants producing more grains per plant (187.6 vs. 171.3) and higher yield per plant (28.8 vs. 25.7 g). Results indicated that biostimulant application improved physiological performance and increased soybean yields, comparable to full-rate phosphorus, highlighting its potential as a sustainable approach under increasing environmental and input-related challenges.

Excel-based spreadsheet (Biochar manure TEC.xlsx) can be used to adjust the livestock and cropland inputs and explore technoeconomic outcomes of farm-specific stored manure treatment with biochar and subsequent application to cropland soil.

Excel-based spreadsheet (Biochar manure TEC.xlsx) can be used to adjust the livestock and cropland inputs and explore technoeconomic outcomes of farm-specific stored manure treatment with biochar and subsequent application to cropland soil.