Barley ( Hordeum vulgare L.) is used mainly for malting, brewing, and animal feed. In antiquity, barley was a major calorie source for humans and has recently become of increased interest as consumers seek healthier options. Hull‐less barley plays a key role in this resurgence as the need to process barley through pearling is removed and modern cultivars have high fiber content. To our knowledge, no work has established fertilizer‐nitrogen (N) recommendations for hull‐less food barley under high‐yielding irrigated conditions common in the semi‐arid western United States. Research was conducted in the major irrigated production area of southern Idaho over 11 site‐years of replicated N response trial data (∼5 fertilizer‐N rates) from 2019 to 2023 for the cultivars Goldenhart and Julie. N‐supply is reported and is the sum of applied fertilizer‐N and soil inorganic‐N to 60 cm. Analysis of variance (ANOVA) critical N‐supply (CNS) was calculated site‐by‐site as the lowest yield that did not differ from the maximum. The average ANOVA CNS was 194 kg N ha −1 across all site‐years. A yield‐based approach and corresponding nitrogen requirements (Nr) from the ANOVA CNS resulted in an N‐supply range from 200 to 224 kg N ha −1 . A 95% relative grain yield (RGY) was used for linear‐ and quadratic‐plateau models which determined CNS of 194 and 234 kg N ha −1 , respectively. Protein increased slightly but was poorly explained by N‐supply. A static‐N range from 194 to 234 kg N ha −1 is suitable for irrigated hull‐less barley production.

The impact of harvest timing on forage yield, nutritional composition, regrowth potential, and economic return was assessed for three awnless forage barley ( Hordeum vulgare L.) (Hays, Haybet, Lavina) and oat ( Avena sativa L.) varieties (Monida, Otana, Ajay) at four phenological stages (boot, heading, milk, or soft‐dough) across three site years at two locations in southern Idaho, United States (Aberdeen 2021–2022, Rexburg 2021). Within a harvest timing, forage barley and oat generally had similar yield and forage nutrient compositions. At each location, forage mass increased with delayed harvests and, averaged across all varieties, yielded 9.35, 1.96, and 7.32 Mg ha −1 at Aberdeen 2021, Aberdeen 2022, and Rexburg 2021, respectively, when harvested at the soft dough stage. It was unprofitable to harvest the crops at the boot or heading stages due to insufficient forage mass production. Forage nutrient composition was greatest when harvested at the boot stage producing a “premium” quality hay (crude protein >13%). Barley and oats harvested after the boot stage had poorer forage nutrient composition but were generally still classified as good quality hays (crude protein between 9% and 13%) suitable for beef/cow‐calf operations ( Bos taurus ), dairy heifers (18–24 months), and non‐lactating cows. Oat (excluding Ajay) and some barley varieties regrew after harvest at the boot or heading stage, but double harvests were typically not as profitable as a single harvest done at soft dough. This study recommends that irrigated forage barley and oats should be harvested at the soft dough stage to maximize yield and profitability.

Nitrogen (N) fertilizer applications near the time of planting are important for upper US Midwest corn (Zea mays L.) production, but wet springs may result in significant N losses. Split applications may circumvent this problem and improve fertilizer uptake and use efficiency, but the relative contribution of N from the soil and fertilizer is poorly understood. A field study with six sites in Minnesota received N-15-labeled urea fertilizer in the first year and unlabeled urea in the second year to determine the effect of N rate and application timing on corn uptake and accumulation patterns of fertilizer-derived N (FDN) and soil-derived N (SDN) over two consecutive growing seasons. Corn responded positively to fertilization. The percentage of total N uptake as FDN was greatest closest to the time of application but decreased over time as SDN became the dominant N source. A split application (45 kg N ha(-1) at planting, 90 kg N ha(-1) at V4) significantly improved FDN uptake over the 135 kg N ha(-1) preplant treatment but did not improve total N uptake in the first year at any site. Fertilizer-N use efficiency ((FNUE)-N-15) using the isotopic method was 2.8%-43.3% across all sites at the end of the first year with the majority partitioned to the grain. At the end of the second year, approximately 2.2% of the first-year applied FDN was recovered in aboveground biomass. Fertilization ensures adequate N availability to the developing crop, but ultimately SDN contributed >= 61% of the total N uptake.

The value of glyphosate to growers practicing minimum or no-till farming has been primarily a function of three factors: broad-spectrum weed control, little to no carryover effect, and cost effectiveness. A 2-year field study was conducted in 2021 and 2022 at the University of Idaho Research and Extension Centers at Kimberly and Aberdeen, ID, to evaluate the efficacy of alternative pre-plant burndown herbicide treatments as compared to glyphosate treatment, the industry standard in small grain production systems. Herbicide cost comparison and crop injury observation were also conducted. Most herbicide treatments provided >=$ \ge $90% control of the predominant weed species at 3 weeks after herbicide application. At least six different herbicide treatments had an equivalent cost to that of glyphosate at $26.50 ha-1. No observable damage from herbicide treatments was observed and crop yield was not affected by the treatments. These factors indicate that there are alternatives to pre-plant burndown herbicides that are equally effective as glyphosate. With combinations of herbicides, each having a different site of action, weed control can be achieved while simultaneously reducing the risk of herbicide resistance. Alternatives to glyphosate for pre-plant weed control would reduce overreliance on glyphosate. Alternative herbicides to glyphosate provided >= 90% control of the predominant weed species. At least six different herbicide treatments were effective and had equivalent costs to glyphosate. No visible crop damage or yield reduction was observed from any of the herbicide treatments.

Preplant weed control is a common practice for many small grain farmers. The timing of these applications often coincides with starter nitrogen (N) fertilizer application. Co-application of the herbicides and N fertilizers, such as urea-ammonium nitrate (UAN), can reduce the number of trips across the field, labor costs, and the costs of N and herbicide applications. However, there is a dearth of information on the effect of herbicide-N fertilizer mixtures on herbicide efficacy. Field studies were conducted in the summer of 2021 and 2022 to evaluate the effect of UAN (32-0-0) rate (0%, 25%, 50%, 75%, and 100% of carrier volume) on the efficacy of three non-selective herbicides (glyphosate [1260 g ae ha(-1)], paraquat [560 g ai ha(-1)], and tiafenacil [74 g ai ha(-1)]). There was no effect of UAN volume on herbicide efficacy. The addition of UAN did not reduce the efficacy of glyphosate, paraquat, or tiafenacil. At 3 weeks after herbicide application, glyphosate efficacy ranged from 92% to 94% (broadleaved weeds) and 97% (grassy weeds). Paraquat efficacy ranged from 63% to 87% (broadleaved weeds) and 87% (grassy weeds). Tiafenacil efficacy ranged from 52% to 74% (broadleaved weeds) and 70% (grassy weeds). Higher application volume may be needed to increase the efficacy of contact herbicides such as paraquat and tiafenacil.

Abstract Ammonia (NH3) emissions are an economically and environmentally significant loss pathway of fertilizer and soil‐derived N. Chambers are a commonly used method to quantify NH3 emissions in plot‐scale agricultural research. Although this method is widely used, its accuracy may be influenced by the overall design of the chamber, its components, and its interaction with the environment. Four NH3 chamber designs, including open, open + polytetrafluoroethylene (PTFE), semi‐open, and closed, were deployed over a dilute NH3 solution for 6 h on four dates to determine the effect of chamber design on NH3 capture efficiency. The solution volume and concentration were measured before and after acid trap deployment, and total volatile NH3 emission was assumed to be equal to the mass N loss. The NH3 capture efficiency relative to the estimated total emissions was greatest for the open design (12.9%), whereas the semi‐open chamber was the least efficient (3.5%). The closed chamber reduced NH3 emissions relative to the open and semi‐open designs by inhibiting convective gas transport beneath the chamber footprint.

Active canopy sensing may improve corn (Zea mays L.) nitrogen (N) management, but little has been done to evaluate soil N content to improve the utility of sensors. This study investigated the usefulness of integrating canopy sensing tools and soil N content to estimate grain yield and N requirement at various corn development stages. Six to seven N rates at 35-45 kg urea-N ha(-1) increments were pre-plant applied in 12 sites throughout Minnesota. Canopy-sensing measurements were obtained at the V4, V8, V12, and R1 stages. Soil (0-30 and 0-60 cm) NH4-N and NO3-N concentrations were measured at the V4, V8, and V12 stages. Adjusting sensor measurements with soil NO3-N (0-30 cm) measured at the V4 stage provided the best trade-off between gains in prediction accuracy and practicality for soil sampling. At the V4 stage, predictions of N requirement with soil N alone (RMSE = 41.3 kg N ha(-1)) and soil-N-adjusted sensor measurements (RMSE ranging from 39.6 to 42.7 kg N ha(-1)) were similar but better than predictions with unadjusted sensor measurements (RMSE ranging from 61.0 to 72.9 kg N ha(-1)). Although the utility of canopy sensing without soil-N adjustments improved at later development stages, the most accurate predictions of N requirement were obtained with soil-N-adjusted sensor measurements collected at V8 and V12 (RMSE as low as 32.5 kg N ha(-1)). Our study shows that early-season canopy sensing (up to V8) coupled with soil N measurements may be a viable alternative to improve in-season N management.

Many nitrogen fertilizer studies evaluate the overall effect of a treatment on end-of-season measurements such as grain yield or cumulative N losses. A stable isotope approach is necessary to follow and quantify the fate of fertilizer derived N (FDN) through the soil-crop system. The purpose of this paper is to describe a small-plot research design utilizing non-confined 15N enriched microplots for multiple soil and plant sampling events over two growing seasons and provide sample collection, handling, and processing protocols for total 15N analysis. The methods were demonstrated using a replicated study from south-central Minnesota planted to corn (Zea mays L.). Each treatment consisted of six corn rows (76 cm row-spacing) 15.2 m long with a microplot (2.4 m by 3.8 m) embedded at one end. Fertilizer-grade urea was applied at 135 kg N∙ha-1 at planting, while the microplot received urea enriched to 5 atom % 15N. Soil and plant samples were taken several times throughout the growing season, taking care to minimize cross-contamination by using separate tools and physically separating unenriched and enriched samples during all procedures. Soil and plant samples were dried, ground to pass through a 2 mm screen, and then ground to a flour-like consistency using a roller jar mill. Tracer studies require additional planning, sample processing time and manual labor, and incur higher costs for 15N enriched materials and sample analysis than traditional N studies. However, using the mass balance approach, tracer studies with multiple in-season sampling events allow the researcher to estimate FDN distribution through the soil-crop system and estimate unaccounted-for FDN from the system.

Nitrogen (N) is essential to produce high yielding corn (Zea mays L.), but excess fertilization before rapid corn N uptake may result in N loss from the soil-corn system that reduces fertilizer N use efficiency, causes an economic loss for producers, and negatively impacts the environment. Urea fertilizer applications at planting are common, but recent years of wet springs in the U.S. upper Midwest has fostered a greater interest in split-applications that may avoid early spring N loss and improve fertilizer N supply to the crop. Fertilizer N rate, application timing, soil physical and chemical properties, and weather patterns can modify fertilizer-derived N distribution (FDN) in the soil profile, uptake by the crop, and potential for N loss in the year of application and subsequent years. Thus, the objectives of this study were to investigate the effects of fertilizer N rate and application timing on 1) FDN distribution and form in the soil, 2) FDN and soil-derived N (SDN) uptake and partitioning by the corn crop, and 3) fertilizer recovery and reuse in the soil-corn system over two consecutive growing seasons. Three studies were initiated in both 2014 (Becker14, Clara City14, Waseca14) and 2015 (Becker15, Lamberton15, Waseca15) in Minnesota, at sites that represented agronomically important soils. Urea fertilizer (46% N) was applied at planting at 45 kg N ha-1 increments from 0 to 270 or 315 kg N ha-1. An additional treatment was split-applied as 45 kg N ha-1 at planting and 90 kg N ha-1 when the corn had four fully developed leaves (V4). Labeled 15N urea (5 atom %) fertilizer was applied to microplots in the 45, 135, and 225 kg N ha-1 treatments, as well as the 45/90 kg N ha-1 split-application treatment. Soil samples were collected in the first growing season within eight days of 15N urea fertilizer application (PA), when the corn had eight fully developed leaves (V8), at tasseling (R1), and post-harvest (PHY1). In the second growing season, soil samples were collected at pre-plant (PPY2) and post-harvest (PHY2). Aboveground plant samples were collected at V8, R1, and physiological maturity (R6) in the first growing season, and R6 in the second growing season. At PA, 63 to 112% of FDN was recovered from the top 60 cm of the soil profile across all sites, except Becker14 and Clara City14 where 55 and 43% of the applied FDN were recovered by corn averaged across all treatments, respectively. Low recovery of FDN at Becker14 was likely due to N leaching through the loamy sand soil profile following greater-than-normal April through June precipitation. At Clara City14, low recovery of FDN was due to NH3 volatilization from inadequate incorporation of urea into the soil profile. Of the total FDN in the soil at PA, 72 to 90% was in the soil organic N fraction and temporarily protected from loss. The majority of soil FDN was in the top 15 cm of the soil profile, but FDN was observed in all soil sampling depths indicating that leaching of NO3- and soluble organic FDN is rapid irrespective of the soil texture. The soil…

Optical canopy sensing tools may improve corn (Zea mays L.) nitrogen (N) management, but their usefulness in far northern latitudes remains unclear. For this reason, the utility of SPAD, GreenSeeker normalized difference vegetation index (GS-NDVI), RapidSCAN normalized difference vegetation index (RS-NDVI), and RapidSCAN normalized difference red edge (RS-NDRE) were evaluated to predict corn grain yield, plant N accumulation, and plant N deficiency in 12 site-years throughout Minnesota. Six to seven N rates (35-45 kg urea-N ha(-1) increment) were pre-plant applied. Canopy sensing measurements and aboveground plant N accumulation were obtained at V4, V8, V12, and R1 stages. Regardless of the tool, low predictive power of grain yield, plant N accumulation, and N deficiency occurred at V4, likely because of low crop N demand and sufficient N supply. At V8, sensors provided good estimations of grain yield (R-2 = .75-.85) but underestimated the agronomic optimum nitrogen rate (AONR) by 33, 94, 102, and 46 kg N ha(-1) with the SPAD, GS-NDVI, RS-NDVI, and RS-NDRE, respectively. At V12 RS-NDRE measurements provided the most accurate estimations of grain yield (R-2 = .92) and AONR [R-2 = .84 and N rate differential from agronomic optimum nitrogen rate (dAONR) at -2 kg N ha(-1)]. At R1 SPAD also provided good estimations of grain yield and N deficiency. The mismatch between the best timings for predicting N fertilizer requirements (V12 and R1) and the best timings for sidedressing (V4-V8) highlight that sensing tools may have limited utility to improve the standard maximum return to N approach in the Upper Midwest.

Core Ideas Soil texture and precipitation largely impact split fertilizer application efficacy. Split fertilizer application consistently increased grain yield in irrigated sands. In fine‐texture and well distributed rain, split application should be done by V8. In fine‐texture and poor distributed rain, split application made no yield difference. Corn response to split application was greater in coarse‐textured than fine‐textured soils. In‐season N fertilization is increasingly being used as a management strategy to reduce risk of N loss to the environment. This study evaluated the optimal timing for a split N fertilizer application in corn ( Zea mays L.) across different environments and soil textural classes in Minnesota. Treatments consisted of pre‐plant (PP) urea applied at 0 to 270 or 315 kg N ha −1 on increments of 45 kg N ha −1 and five split applications (SA) of 45 kg N ha −1 urea ammonium nitrate as starter fertilizer and 90 kg N ha −1 of urea with an urease inhibitor applied at the V2, V4, V6, V8, or V12 stage of corn phenological development. Site‐years were grouped according to grain yield response to fertilizer timing. Irrigated coarse‐textured soils produced 1.5‐ to 1.9‐fold greater grain yield when fertilizer was split applied from V4 to V12 due to improved synchrony of N availability to crop demand and reduced potential for NO 3 –N leaching. Rainfed, fine‐textured soils had mixed results. Site‐years receiving well‐distributed precipitation produced greater grain yield when fertilizer was split applied from V2 to V8, but early season N deficiency reduced yield for the V12 application. Site‐years with limited precipitation during the late vegetative through grain filling stages of corn had no improvement in grain yield or N use efficiencies for SA because dry soil conditions likely interfered with root development and made N fertilizer positionally unavailable to the crop. This study highlights that the success of SA is largely dictated by soil texture and precipitation.