Microbial Proxies for Anoxic Microsites Vary with Management and Partially Explain Soil Carbon Concentration.

Anoxic microsites are potentially important but unresolved contributors to soil organic carbon (C) storage. How anoxic microsites vary with soil management and the degree to which anoxic microsites contribute to soil C stabilization remain unknown. Sampling from four long-term agricultural experiments in the central United States, we examined how anoxic microsites varied with management (e.g., cultivation, tillage, and manure amendments) and whether anoxic microsites determine soil C concentration in surface (0-15 cm) soils. We used a novel approach to track anaerobe habitat space and, hence, anoxic microsites using DNA copies of anaerobic functional genes over a confined volume of soil. No-till practices inconsistently increased anoxic microsite extent compared to conventionally tilled soils, and within one site organic matter amendments increased anaerobe abundance in no-till soils. Across all long-term tillage trials, uncultivated soils had ∼2-4 times more copies of anaerobic functional genes than their cropland counterparts. Finally, anaerobe abundance was positively correlated to soil C concentration. Even when accounting for other soil C protection mechanisms, anaerobe abundance, our proxy for anoxic microsites, explained 41% of the variance and 5% of the unique variance in soil C concentration in cropland soils, making anoxic microsites the strongest management-responsive predictor of soil C concentration. Our results suggest that careful management of anoxic microsites may be a promising strategy to increase soil C storage within agricultural soils.

Spring applied phosphorus loss with cover crops in no-till terraced field.

Cover crops (CC) can improve phosphorus (P) cycling by reducing water related P losses and contributing to P nutrition of a rotational crop. This is particularly important in claypan soils with freeze-thaw cycles in early spring in the Midwest U.S. This 4-year study (2019-2022) examined the impact of CC monoculture and mix of CC species on P losses from a fertilizer application, and determined the P balance in soil compared to no cover crop (noCC). The CC mix consisted of wheat (Triticum aestivum L.), radish (Raphanus raphanistrum subsp. Sativus), and turnip (Brassica rapa subsp. Rapa) (3xCCmix) in 2019 and 2021 before corn, and cereal rye (Secale cereale L.) was planted as monoculture before soybean in 2020 and 2022. The 3xCCmix had no effect on total phosphorus (TP) and dissolved reactive phosphorus (PO4-P) concentration or load in 2019 and 2021. Cereal rye reduced TP and PO4-P load 70% and 73%, respectively, compared to noCC. The variation in soil moisture, temperature, and net precipitation from fertilizer application until CC termination affected available soil P pools due to variability in CC species P uptake, residue decomposition, and P loss in surface water runoff. Overall, the P budget calculations showed cereal rye had 2.4 kg ha-1 greater P uptake compared to the 3xCCmix species which also reduced P loss in water and had greater differences in soil P status compared to noCC. This study highlights the benefit of CCs in reducing P loss in surface runoff and immobilizing P through plant uptake. However, these effects were minimal with 3xCCmix species and variability in crop residue decomposition from different CC species could affect overall P-soil balance.

Epichloë fungal endophyte interactions in perennial ryegrass (Lolium perenne L.) modified to accumulate foliar lipids for increased energy density.

BACKGROUND: Commercial cultivars of perennial ryegrass infected with selected Epichloë fungal endophytes are highly desirable in certain pastures as the resulting mutualistic association has the capacity to confer agronomic benefits (such as invertebrate pest deterrence) largely due to fungal produced secondary metabolites (e.g., alkaloids). In this study, we investigated T2 segregating populations derived from two independent transformation events expressing diacylglycerol acyltransferase (DGAT) and cysteine oleosin (CO) genes designed to increase foliar lipid and biomass accumulation. These populations were either infected with Epichloë festucae var. lolii strain AR1 or Epichloë sp. LpTG-3 strain AR37 to examine relationships between the introduced trait and the endophytic association. Here we report on experiments designed to investigate if expression of the DGAT + CO trait in foliar tissues of perennial ryegrass could negatively impact the grass-endophyte association and vice versa. Both endophyte and plant characters were measured under controlled environment and field conditions. RESULTS: Expected relative increases in total fatty acids of 17-58% accrued as a result of DGAT + CO expression with no significant difference between the endophyte-infected and non-infected progeny. Hyphal growth in association with DGAT + CO expression appeared normal when compared to control plants in a growth chamber. There was no significant difference in mycelial biomass for both strains AR1 and AR37, however, Epichloë-derived alkaloid concentrations were significantly lower on some occasions in the DGAT + CO plants compared to the corresponding null-segregant progenies, although these remained within the reported range for bioactivity. CONCLUSIONS: These results suggest that the mutualistic association formed between perennial ryegrass and selected Epichloë strains does not influence expression of the host DGAT + CO technology, but that endophyte performance may be reduced under some circumstances. Further investigation will now be required to determine the preferred genetic backgrounds for introgression of the DGAT + CO trait in combination with selected endophyte strains, as grass host genetics is a major determinant to the success of the grass-endophyte association in this species.

Nutrient loss from floodplain soil with controlled subsurface drainage under forage production.

Expansion of subsurface drainage into forage production may have a deleterious effect on surface waters due to increased nitrogen and phosphorus loading. The impact of controlled subsurface drainage (CD) on nitrogen and phosphorus loss compared with free subsurface drainage (FD) in tile drainage water has been explored to a lesser extent from forage production systems. This study quantifies the effects of CD and FD on average seasonal concentrations and cumulative loads of the total suspended solids (TSS), nitrate nitrogen (NO3 -N), and dissolved reactive phosphorus (DRP) in subsurface drainage water from a poorly drained floodplain soil in a cereal rye (Secale cereale L.)-sorghum [Sorghum bicolor (L.) Moench] rotation with rotational cattle grazing. During all crop seasons of sorghum production (2010-2013), CD had 6.03-9.63 mg L-1 less NO3 -N than FD. Mean DRP concentration was significantly higher for CD than for FD during all seasons except for sorghum in 2012-2013. Average cumulative discharge was 38 and 314 m3 ha-1 less for CD than for FD during sorghum and cereal rye growing seasons, respectively. Controlled drainage had 0.68-6.14 kg ha-1 lower cumulative NO3 -N loads than FD. The DRP loads were dependent on discharge. During sorghum growing seasons, TSS and DRP loads were 79-90% lower in CD compared with FD. The ability to reduce drainage water flow from tiles and subsequent nitrogen and phosphorus loading with CD compared with FD in a floodplain soil indicates that CD can be effective best management practice for forage production systems.

Urea Nitrapyrin Placement Effects on Soil Nitrous Oxide Emissions in Claypan Soil.

Corn ( L.) production in poorly drained claypan soils in the US Midwest is a challenge due to low soil permeability, which may result in wetter soil conditions and relatively large amounts of soil NO emissions early in the growing season. The objectives of this study were to determine the effects of urea fertilizer placement with and without nitrapyrin (NI) on daily and cumulative soil NO emissions, and yield-scaled NO emissions in 2016 and 2017. Treatments included urea deep banded to a 20-cm depth (DB), urea deep banded to 20 cm plus NI (DB+NI), urea incorporated after a surface broadcast application to ∼8-cm depth (IA), urea broadcast on the soil surface (SA), and a nonfertilized control (NTC). Fertilizer was applied at 202 kg N ha. Surface soil NO efflux rates were generally lower (<50 g NO-N ha d) during the first 3 wk after N fertilization and latter parts of the growing seasons. When averaged across the 2016 and 2017 growing seasons, all fertilized treatments had significantly greater (2.33-5.60 kg NO-N ha, < 0.05) cumulative soil NO emissions than NTC. The DB+NI treatment had 54 and 55% lower cumulative soil NO emissions than IA and SA, respectively. In 2017, DB+NI had similar soil yield-scaled NO emissions to NTC. Percentage grain yield increase over NTC was highest for DB and DB+NI. Grain yield in 2016 was 14 to 18% higher for DB and DB+NI than SA. Results suggest that DB+NI is an effective management strategy for reducing cumulative soil NO emissions and increasing grain yields over the growing season.

DRD4 Genotype and the Developmental Link of Peer Social Preference with Conduct Problems and Prosocial Behavior Across Ages 9-12 Years.

The peer environment is among the most important factors for children's behavioral development. However, not all children are equally influenced by their peers, which is potentially due to their genetic make-up. The dopamine receptor D4 gene (DRD4) is a potential candidate gene that may influence children's susceptibility to the peer environment. In the present study, we explored whether variations in the DRD4 gene moderated the association between children's social standing in the peer group (i.e., social preference among classmates) with subsequent conduct problems and prosocial behavior among 405 (51% females) elementary school children followed annually throughout early adolescence (ages 9-12 years). The behavioral development of children with and without the DRD4 7-repeat allele was compared. The results indicated that children who had higher positive social preference scores (i.e., who were more liked relative to disliked by their peers) showed less conduct problem development in subsequent years relative to children who had lower positive social preference scores. In contrast, children who had more negative preference scores (i.e., who were more disliked relative to liked among peers) showed more conduct problem development in subsequent years, relative to children who had less negative preference scores. However, these effects only occurred when children had a 7-repeat allele. For children who did not have a 7-repeat allele, the level of social preference was not associated with subsequent conduct problems. No evidence for gene-environment interaction effects for prosocial behavior was found. The implications for our understanding of conduct problem development and its prevention are discussed.

Reducing phosphorus loss in tile water with managed drainage in a claypan soil.

Installing subsurface tile drain systems in poorly drained claypan soils to improve corn ( L.) yields could potentially increase environmental phosphorus (P) loss through the tile drainage system. The objectives of the study were to quantify the average concentration and loss of ortho-P in tile drain water from a claypan soil and to determine whether managed subsurface drainage (MD) could reduce ortho-P loss in tile water compared with free subsurface drainage (FD). Flow-weighted ortho-P concentration in the tile water was significantly lower with MD (0.09 mg L) compared with that of FD (0.15 mg L). Ortho-P loss in the tile water of this study was reduced with MD (36 g ha) by 80% compared with FD (180 g ha). Contrary to previous research, reduced ortho-P loss observed over the 4-yr study was not solely due to the reduced amount of water drained annually (63%) with MD compared with FD. During the spring period, when flow was similar between MD and FD, the concentration of ortho-P in the tile water generally was lower with MD compared with FD, which resulted in significantly less ortho-P loss with MD. We speculate that MD's ability to conserve water during the dry summer months increased corn's uptake of water and P, which reduced the amount of P available for leaching loss in the subsequent springs.

Twins, tissue, and time: an assessment of SNPs and CNVs.

With the desire to assess genetic variation across the lifespan in large-scale collaborative projects, one question is whether inference of copy number (CN) is sensitive to the source of material for deoxyribonucleic acid (DNA) analysis (e.g., blood and buccal) and another question is whether CN is stable as individual sage. Here, we address these questions by applying Affymetrix 6.0 single nucleotide polymorphism (SNP)micro-arrays to 1,472 DNA samples from 710 individuals from the Netherlands Twin Register, including twin and non-twin individuals (372 with buccal and blood derived DNA and 388 with longitudinal data).Similar concordance for CN and genotype inference between samples from the same individual [or from the monozygotic (MZ) co-twins] was found for blood and buccal tissues. There was a small but statistically significant decrease in across-tissue concordance compared with concordance of samples from the same tissue type. No temporal effect was seen on CN variation from the 388 individuals sampled at two time points ranging from 1 to 12 years apart. The majority of our individuals were sampled at age younger than 20 years. Genotype concordance was very high (~ > 99%) between co-twins from 43 MZ pairs. For75 dizygotic (DZ) pairs, ~was ~65%. CN estimates were highly consistent between co-twins from MZ pairs for both deletions (f?2 ~ 90%) and duplications (~ ~ 86%). For DZ, these were similar for within-individual comparisons, but naturally lower between co-twins (~ ~ 50-60%). These results suggest that DNA from buccal samples perform as well as DNA from blood samples on the current generation of micro-array technologies.