Abstract Knowing a cover crop's carbon to nitrogen (C/N) ratio can help growers time termination to optimize N release. But growers lack simple methods to predict important C/N ratios like 20, an often‐cited “tipping point” between N mineralization and immobilization. We evaluated if Feekes growth stage, days after planting (DAP), and growing degree days (GDD) could predict C/N ratio changes of cereal cover crops. We tracked C/N changes monthly in rye ( Secale cereale L. ‘Merced’) and triticale (x Triticosecale Wittmack, ‘Pacheco’) in five biweekly trials sown from October 1 to November 30, 2021, and related these changes to farmer‐friendly metrics: DAP, GDD, and development. Growth stage and GDD were strongly correlated, as were DAP and C/N. The C/N ratios (1) increased with increasing GDD, DAP, and growth stage, (2) were similar for both cereals, and (3) became more variable over time. With exception of one trial, planted on November 15 where N was more limited, shoot biomass reached a C/N ratio of 20 when October‐planted cover crops were at Feekes 10.1 (heading, 97–103 DAP) and Feekes 8 (flag leaf just visible, 94–98 DAP) in November plantings. Excluding the 15 Nov. trial, fitted regressio curves up to ≈150 DAP showed that a C/N of 20 occurred by 94 to 102 DAP, for October‐ and November‐plantings, respectively. Accumulated GDD to reach a C/N of 20 varied with planting date ranging from approximately 650 to 900 GDD, and tended to decrease with later plantings. Our data illustrate the value and complexity of using growth stage, GDD, and DAP to predict the C/N ratio changes in cover crops. This will help farmers optimize cover crop management and comply with a new California regulation to reduce N leaching to groundwater.

Abstract Combining regenerative agriculture (RA) practices, such as cover cropping and no‐till, is increasingly promoted as a strategy to enhance soil health and climate resilience. However, their long‐term impacts on crop yield and yield stability remain uncertain. In this study, we assessed how RA practices influence sub‐field spatial variability of crop yield. We use yield stability zone categories (high, medium, low, or unstable) across 10 commercial farm fields in Michigan over a long period of time, 6–9 years before RA were implemented and 9–10 years after RA were implemented. We found that RA practices did not statistically impact maize ( Zea mays L.; +9%) or soybean ( Glycine max (L.) Merr.; –3%) yields, but RA increased whole field yield stability (decrease of CV from 27% to 17%) and the proportion of high‐yielding zones within the fields (+28%) due to the conversion of a substantial portion (21%) of prior unstable yielding areas of the field. Our results suggest that combining RA practices, such as no‐till and cover crops, can improve crop productivity and yield stability through the conversion of unstable zones into more stable areas of crop production, benefiting long‐term soil health and broader environmental goals in the Upper US Midwest.

Abstract Thrips (Thysanoptera: Thripidae) are consistent pests in cotton ( Gossypium hirsutum ) production during the early season. In addition to cultural and chemical practices for thrips management, a new Bt ( Bacillus thuringiensis ) trait called ThryvOn is available for thrips management. However, research investigating crop development and yield response to this new technology is limited. Therefore, a field trial was implemented in Tifton, GA, USA, to evaluate thrips prevalence, plant injury, crop development, and lint yield in response to cultivar (with or without ThryvOn) and insecticide treatment under high thrips pressure. ThryvOn cotton exhibited lower thrips densities and plant injury due to thrips than non‐ThryvOn cotton, regardless of insecticide treatment. When interactions between cultivar and insecticide were observed, insecticide treatment reduced pest pressure and positively impacted plant growth to a larger extent in non‐ThryvOn cotton compared to ThryvOn cotton. Similar observations were made for radiation capture by the crop canopy, although significant effects were only observed on one sample date in a single growing season. Lint yields were not affected by cultivar or insecticide treatment in either year, despite significant plant injury in the early season. The data from this study further highlight that newly available ThryvOn varieties offer significant thrips injury protection relative to non‐ThryvOn varieties, decreasing the need for insecticide application. Thrips injury and reductions in plant growth in the early season may not necessarily translate to yield loss if radiation capture by the crop canopy is eventually maximized and there is sufficient growing season length available to mature the crop.

Abstract Triticale (x Triticosecale ) silage has become a popular choice for many dairy producers to increase forage supply. Using fertilization to increase protein concentrations in triticale silage may be an economic strategy for dairies to increase ration protein concentrations and offset the expense of purchased protein sources. The objective of this study was to investigate the effect of increasing nitrogen fertilizer rates with and without sulfur on triticale yield and quality. Triticale was established at two locations in Maryland in the fall of 2020, 2021, and 2022. Fertility treatments included a no‐nitrogen control along with low (56 kg ha −1 ), medium (112 kg ha −1 ), and high (168 kg ha −1 ) levels of nitrogen, each with and without added sulfur (17 kg ha −1 ). Fertility treatments were applied in March of each year in a split‐plot design with four replicates at each location. Plots were mechanically harvested when forage reached the boot stage in late April. Harvested forage was weighed and subsampled for dry matter yield determination and forage analysis. Statistical analysis was conducted using mixed model analysis. The application of nitrogen increased forage yields in 4 of 6 site‐years, irrespective of sulfur inclusion. In 2021, crude protein concentrations increased linearly with nitrogen application rates from 87 to 180 g kg −1 , irrespective of sulfur inclusion; however, this same effect was not seen in 2022–2023. Triticale neutral detergent fiber and net energy concentrations did not differ. The results indicate that increasing nitrogen application rates can influence forage yield and crude protein content in some cases.

Abstract Variable‐rate (VR) technology allows for changing nutrient rates within fields. This study compared VR and uniform‐rate (UR) potassium (K) fertilization for corn ( Zea mays L.)–soybean [ Glycine max (L.) Merr.] rotations. Grid soil‐sampling (0.1–0.3 ha cells), global positioning systems (GPS), and yield monitors were used to establish multiyear strip trials on eight Iowa fields (29 site‐years). Treatments were a control and K for the 2‐year rotation applied once before corn or soybean using UR or VR based on soil‐test K (STK). Strip‐mean yields showed increases ( p ≤ 0.10) in 15 site‐years, but the application methods differed only in two. Potassium increased yield in 39 of 60 instances with STK Very Low, Low, or Optimum (<171 mg kg −1 ), but in three of 23 instances with higher STK. The application method did not influence yield response to K consistently in analyses by site but on average across sites and crops, VR increased yield 3.2% more than UR with Very Low STK (<91 mg kg −1 ). Across all site‐years, VR applied 17% less K than UR and increased STK of low‐testing soils (<130 mg kg −1 ) 40% more than UR, with inconsistent effects in high‐testing soils, which represents cost savings and increased K use efficiency. We conclude that the K application methods seldom differed, but on average across fields, reduced the amount of K applied and increased STK of low‐testing areas more than UR. Results contribute to farmers’ understanding about the potential advantages of VR for K management but also its limitations.

Abstract Stripe rust, caused by Puccinia striiformis f. sp. tritici , significantly reduces wheat ( Triticum aestivum L.) yields when uncontrolled. This study developed predictive models for stripe rust severity using weather variables. Field experiments were conducted from 2017 to 2019 at the Research Farm, Chatha, using susceptible wheat variety PBW 343 in a randomized block design with four replications. Disease severity was assessed weekly using the modified Cobb scale. Additional historical weather and disease data from 2005 to 2017 were incorporated to develop comprehensive forecasting models. Strong positive correlations were observed between disease severity and maximum temperature ( r = 0.89–0.91) and minimum temperature ( r = 0.75–0.91), while morning relative humidity showed negative correlation ( r = −0.80). Rainfall exhibited no significant correlation with disease progression. Two multiple linear regression models were developed: for 2005–2017, Y = −502.14 + 0.64 X 1 + 8.57 X 2 + 3.04 X 3 + 1.42 X 4 + 0.58 X 5 ; and for 2017–2019, Y = 322.57 + 9.41 X 1 − 4.14 X 2 − 2.56 X 3 − 0.71 X 4 + 0.26 X 5 , where Y represents disease severity and X 1 – X 5 represent weather parameters. Both models explained approximately 89%–91% of variation in disease severity. Spore concentration increased 84% from 51st to seventh standard meteorological week during 2017–2019. These models provide quantitative tools for predicting stripe rust severity using readily available weather data, enabling timely disease management decisions and supporting sustainable wheat production.

Abstract The application of composted sewage sludge (CSS) in crop production offers a sustainable solution for nutrient recycling and reducing reliance on mineral fertilizers. This study evaluated the residual effects of CSS on phosphorus (P) bioavailability and agronomic performance of maize and cover crops in P‐fixing soils of the Brazilian Savannah ( Cerrado ). A field experiment was conducted over three cropping cycles (third, fourth, and fifth season), applying CSS at rates of 0, 5, 7.5, 10, and 12.5 Mg ha − 1 (wet basis) alongside conventional mineral fertilizer. The results showed that CSS significantly enhanced P uptake and maize ( Zea mays L.) yield, with linear increases in plant height and grain yield (up to 28%) in the third season. Marandu grass ( Urochloa brizantha (A. Rich.) T.Q. Nguyen cv. Marandu) growth responded positively to CSS, while a cover crop mix showed no response. Soil available P increased linearly with CSS rates, though climatic variability influenced outcomes. This work shows CSS demonstrates potential as a sustainable P source, but its efficacy depends on management practices and environmental conditions.

Abstract Biomass sorghum [ Sorghum bicolor (L.) Moench] is an alternative biofuel feedstock to maize [ Zea mays (L.)]. One advantage of biomass sorghum over maize is relatively lower nitrogen (N) requirement and its ability to tolerate late planting or fit into double cropping systems. To evaluate the most economic rate of N (MERN) for biomass sorghum in the Mid‐Atlantic region, a 3‐year (2017, 2018, and 2019) field trial was conducted at two locations (Holland and Hare) in Southeastern Virginia. Treatments were two planting dates (early [EP] versus late [LP]) and seven N rates (0, 56, 112, 168, 224, 280, and 336 kg ha −1 ) conducted in six environments. Data on dry matter yield of biomass sorghum, plant height, stem diameter, susceptibility to foliar diseases, and stalk lodging were recorded. Between the two planting dates, EP had 52%, 19%, and 16% higher dry matter, plant height, and stem diameter, respectively, compared to LP. However, LP exhibited lower disease pressure in four of 6 site‐years and lodging severity likely in response to weather conditions. Nitrogen rates between 112 and 224 kg ha −1 significantly improved dry matter, plant height, and stem diameter, with lower disease and lodging severity. At the MERN of 123 kg ha −1 , dry matter yield (20.66 Mg ha −1 ), plant height (454 cm), disease (61%), and lodging severity (34%) were least as compared to other treatments. Application of N at 123 kg ha −1 can provide the highest economic return while reducing the potential for N loss in the Mid‐Atlantic region.

Abstract Herbicide spray drift from roadside application sites poses risks of damaging nearby sensitive crops. The objective of this research was to investigate the impact of five herbicides (sulfometuron‐methyl, indaziflam, triclopyr, triclopyr + clopyralid, and 2, 4‐D + dichlorprop) commonly used to manage roadside vegetation at four application rates (0.01x. 0.05x, 0.1x, and 1x of the field rate) and six application timings (18, 12, and 6 weeks before planting, at planting, and 4 and 8 weeks after planting) on corn ( Zea mays L.) and cotton ( Gossypium hirsutum L.). Field studies were conducted at Upper Coastal Plain Research Station in Rocky Mount, NC, in 2022 and 2023. Although herbicide sensitivity varied by crop species, both species presented higher levels of injury and stunting for application conducted at planting and early post‐planting, and at higher rates. In corn, sulfometuron‐methyl caused the greatest damage. When applied at 4 weeks after planting, this herbicides caused injury of 100% and 48%, and height reduction of 66% and 16%, at 0.1x and 0.01x rates, respectively. In cotton, synthetic auxin herbicides, particularly 2, 4‐D + dichlorprop and triclopyr, were the most damaging post‐emergence. For instance, 2, 4‐D + dichlorprop applied 4 weeks after planting at the 0.01× rate caused 78% injury and 25% height reduction. This study highlights the importance of herbicide selection and application timing when spraying along roadsides to minimize the risk of spray drift damaging nearby corn and cotton fields.

Abstract The aim of this study was to evaluate the effectiveness of the Agricultural Production Systems sIMulator (APSIM) model in estimating yield and yield gaps for winter‐sown wheat ( Triticum aestivum L.) and barley ( Hordeum vulgare L .) in Alborz Province, Iran. Initially, the APSIM‐Wheat and APSIM‐Barley sub‐models (version 7.1) were parameterized for the target cultivars, and model performance was evaluated under a variety of conditions. Model calibration and validation required meteorological data, regional agronomic management approaches, and cultivar‐specific genetic coefficients. These data were gathered over a 4‐year period, with both field and on‐farm components. Two‐year field experiments were conducted to calibrate the model at the Atomic Energy Organization farm (2014–2015) and the University of Tehran's Faculty of Agriculture (2016–2017), using a randomized complete block design with 12 treatments (six wheat and six barley cultivars) and three replications. Under optimal conditions, wheat and barley in Alborz Province might produce average grain yields of 10,800 and 10,350 kg/ha, respectively. The yield gap research found that the wheat yield gap at levels 1–4 was 18.5%, 14.9%, 26.5%, and 18.3%, respectively, while the barley yield gap was 29.5%, 3.1%, 24.0%, and 23.7%. Irrigation schedule, total water use, and sowing date were key management factors that influenced yield gaps. The data indicate that using the best agronomic practices can greatly increase productivity and resource efficiency. Furthermore, the APSIM model has been shown to be an effective tool for crop management prediction, scenario analysis, and informed decision‐making.