Linking soil microbial community structure to potential carbon mineralization: A continental scale assessment of reduced tillage

Potential carbon mineralization (Cmin) is a commonly used indicator of soil health, with greater Cmin values interpreted as healthier soil. While Cmin values are typically greater in agricultural soils managed with minimal physical disturbance, the mechanisms driving the increases remain poorly understood. This study assessed bacterial and archaeal community structure and potential microbial drivers of Cmin in soils maintained under various degrees of physical disturbance. Potential carbon mineralization, 16S rRNA sequences, and soil characterization data were collected as part of the North American Project to Evaluate Soil Health Measurements (NAPESHM). Results showed that type of cropping system, intensity of physical disturbance, and soil pH influenced microbial sensitivity to physical disturbance. Furthermore, 28% of amplicon sequence variants (ASVs), which were important in modeling Cmin, were enriched under soils managed with minimal physical disturbance. Sequences identified as enriched under minimal disturbance and important for modeling Cmin, were linked to organisms which could produce extracellular polymeric substances and contained metabolic strategies suited for tolerating environmental stressors. Understanding how physical disturbance shapes microbial communities across climates and inherent soil properties and drives changes in Cmin provides the context necessary to evaluate management impacts on standardized measures of soil microbial activity

Carbon-sensitive pedotransfer functions for plant available water

Currently accepted pedotransfer functions show negligible effect of management-induced changes to soil organic carbon (SOC) on plant available water holding capacity (θAWHC), while some studies show the ability to substantially increase θAWHC through management. The Soil Health Institute\u27s North America Project to Evaluate Soil Health Measurements measured water content at field capacity using intact soil cores across 124 long-term research sites that contained increases in SOC as a result of management treatments such as reduced tillage and cover cropping. Pedotransfer functions were created for volumetric water content at field capacity (θFC) and permanent wilting point (θPWP). New pedotransfer functions had predictions of θAWHC that were similarly accurate compared with Saxton and Rawls when tested on samples from the National Soil Characterization database. Further, the new pedotransfer functions showed substantial effects of soil calcareousness and SOC on θAWHC. For an increase in SOC of 10 g kg–1 (1%) in noncalcareous soils, an average increase in θAWHC of 3.0 mm 100 mm–1 soil (0.03 m3 m–3) on average across all soil texture classes was found. This SOC related increase in θAWHC is about double previous estimates. Calcareous soils had an increase in θAWHC of 1.2 mm 100 mm–1 soil associated with a 10 g kg–1 increase in SOC, across all soil texture classes. New equations can aid in quantifying benefits of soil management practices that increase SOC and can be used to model the effect of changes in management on drought resilience

Irrigated corn grain yield prediction in Florida using active sensors and plant height

Remote sensing is widely utilized in agriculture for estimating corn (Zea mays L.) grain yield (CGY). Few studies have determined if the Normalized Difference Vegetation Index (NDVI) and/or Soil Plant Analysis Development (SPAD) can estimate CGY in Florida. From April to August 2022, in Live Oak, Florida, a field-scale experiment was conducted in two sites with irrigated corn using a complete randomized block design with six nitrogen (N) rates and four replicates per site. This study aimed to estimate CGY using NDVI alone or in combination with SPAD, plant height (PH), and N rate. CGY response curve served as a comparison standard. Fifteen data subsets were selected, and stepwise selection multiple linear regression analysis was utilized to generate each reduced equation (Model). In addition, the relative significance of the predictor variables was evaluated. The strongest correlations with CGY were demonstrated by N rate (r = 0.93), PH103 (r = 0.91), NDVI39 (r = 0.81), and SPAD60 (r = 0.93). Models with multiple variables showed a better fit than single-variable models. Model 15 (variables until tasseling - 60 DAP) demonstrated comparable performance with 92.8% of variance explained and RMSE = 1,315.685 kg ha−1. Regardless of the model, the N rate has always contributed the most to CGY. Although Model 1 had the best overall performance, it may not be feasible for growers to utilize a model with multiple terms. Consequently, Model 15 could estimate CGY in Florida based on PH and NDVI at 60 and 32 DAP, respectively

Dithiopyr Controls Common Lespedeza (Kummerowia striata) in Bermudagrass

[EN] Common lespedeza is a problematic summer annual weed in bermudagrass lawns, with limited PRE herbicides available for control. Dithiopyr is a pyridine herbicide primarily used for PRE grassy weed control but has shown potential efficacy for controlling annual legumes. The objectives of this research were to evaluate efficacy and behavior of dithiopyr in common lespedeza. In a 3-yr field experiment, sequential dithiopyr applications at 0.42 or 0.56 kg ai ha(-1) beginning in late winter and single applications of dithiopyr at 0.56 kg ai ha(-1) in spring controlled common lespedeza >= 88%. Single and sequential applications of indaziflam at 0.035 and 0.053 kg ai ha(-1) provided poor control ( 80% of C-14 in the treated leaf at 72 h after treatment (HAT). Common lespedeza translocated 6 times more root-absorbed C-14 to shoots than bermudagrass and had 2.8 times greater absorption (Bq mg(-1)) at 72 HAT. In metabolism experiments, parent herbicide levels measured >= 84% of extracted C-14 in both species at 1, 3, and 7 d after treatment. Overall, dithiopyr effectively controls common lespedeza in bermudagrass as a PRE treatment in spring. Susceptibility of common lespedeza to dithiopyr is associated with acropetal translocation and greater herbicide concentrations compared with a tolerant species, bermudagrass.The authors thank Seth Williams for technical assistance with this research, and Anita Alexander from Dow Agrosciences for support with field experiments and providing radiolabeled dithiopyr. We also thank the PAID-00-12, I + D Programe from the Universitat Politecnica de Valencia for supporting the sabbatical work of D.G. at the University of Georgia.Gómez De Barreda, D.; Singh, R.; Sidhu, SS.; Mccullough, PE. (2015). Dithiopyr Controls Common Lespedeza (Kummerowia striata) in Bermudagrass. Weed Science. 63(2):539-545. https://doi.org/10.1614/WS-D-14-00117.1S53954563

Dithiopyr Efficacy, Absorption, and Fate in Annual Bluegrass, Goosegrass, Smooth Crabgrass and Tall fescue

[EN] Dithiopyr provides pre- and early postemergence (POST) control of smooth crabgrass [Digitaria ischaemum (Schreb.) Schreb. ex Muhl] in tall fescue (Festuca arundinacea Schreb.), and may allow greater application flexibility in spring than other herbicides. Dithiopyr also provides preemergence (PRE) control of annual bluegrass (Poa annua L.) and goosegrass [Eleusine indica (L.) Gaertn.], but POST applications are ineffective and may result from differential physiological fate compared to smooth crabgrass. Experiments were conducted to investigate efficacy, absorption, distribution, and metabolism of dithiopyr in annual bluegrass, goosegrass, smooth crabgrass, and tall fescue. From seven dithiopyr rates, 1.18, 1.03, 0.76, and >4.48 kg a. i. ha(-1) were required to reduce shoot mass 50% from the nontreated for annual bluegrass, goosegrass, smooth crabgrass, and tall fescue, respectively. In laboratory experiments, smooth crabgrass had approximate to 75% more kBq kg(-1) following root absorption of C-14-dithiopyr than annual bluegrass, goosegrass, and tall fescue after 72 h. All species recovered >90% of foliar-absorbed C-14 in the treated leaf after 72 h, with limited 14C recovery (<= 5%) in roots and nontreated shoots. Metabolism of dithiopyr increased from 1 to 7 d after treatment (DAT) in all grasses. Final metabolism measured 69, 52, 33, and 27% of total C-14 recovered in smooth crabgrass, goosegrass, annual bluegrass, and tall fescue, respectively. Results suggest relative herbicide concentration and greater metabolism is associated with dithiopyr selectivity for POST control of smooth crabgrass compared to other grassy weeds in turf.Gómez De Barreda, D.; Shidhu Sudeep S.; Yu, JL.; Reed, TV.; Mccullough, PE. (2014). Dithiopyr Efficacy, Absorption, and Fate in Annual Bluegrass, Goosegrass, Smooth Crabgrass and Tall fescue. Agronomy Journal. 106(3):844-850. doi:10.2134/agronj13.0366S844850106