Cover Crop Effect on Subsequent Wheat Yield in the Central Great Plains

Crop production systems in the water-limited environment of the semiarid central Great Plains may not have potential to profitably use cover crops because of lowered subsequent wheat (Triticum asestivum L.) yields following the cover crop. Mixtures have reportedly shown less yield-reducing effects on subsequent crops than single-species plantings. This study was conducted to determine winter wheat yields following both mixtures and single-species plantings of spring-planted cover crops. The study was conducted at Akron, CO, and Sidney, NE, during the 2012–2013 and 2013–2014 wheat growing seasons under both rainfed and irrigated conditions. Precipitation storage efficiency before wheat planting, wheat water use, biomass, and yield were measured and water use efficiency and harvest index were calculated for wheat following four single-species cover crops (flax [Linum usitatissimum L.], oat [Avena sativa L.], pea [Pisum sativum ssp. arvense L. Poir], rapeseed [Brassica napus L.]), a 10-species mixture, and a fallow treatment with proso millet (Panicum miliaceum L.) residue. There was an average 10% reduction in wheat yield following a cover crop compared with following fallow, regardless of whether the cover crop was grown in a mixture or in a single-species planting. Yield reductions were greater under drier conditions. The slope of the wheat water use–yield relationship was not significantly different for wheat following the mixture (11.80 kg ha–1 mm–1) than for wheat following single-species plantings (12.32–13.57 kg ha–1 mm–1). The greater expense associated with a cover crop mixture compared with a single species is not justified

Dual-purpose wheat: Management for forage and grain production

The Oklahoma Cooperative Extension Service periodically issues revisions to its publications. The most current edition is made available. For access to an earlier edition, if available for this title, please contact the Oklahoma State University Library Archives by email at [email protected] or by phone at 405-744-6311

Residue removal and nitrogen cycling in burn and non‐burn Kentucky bluegrass seed production systems

Abstract Kentucky bluegrass (Poa pratensis L.) postharvest residue in northern Idaho has historically been burned to maintain stand life and profitability. Alternatives to open field burning are necessary to reduce adverse impacts of burning on air quality and several have been proposed. However, limited information is available on the impact of residue management on residue removal and nitrogen cycling. In this study, the impact of residue management on residue nutrient dynamics and nitrogen availability was evaluated within replicated full load burn (FLB), bale then burn (BB), bale then mow then harrow (BMH), and system (SYST) (BMH year 1, BB year 2, and FLB year 3) plots in Kootenai County, ID from 2002 to 2006. Standing and non‐standing residues were measured immediately following grass seed harvest and periodically thereafter in each plot. Averaged across years, non‐standing residue (thatch) removal ranged from −13% in BMH to 61% in FLB, and removal of standing biomass ranged from 6% in BMH to 92% in FLB. The combined removal of both non‐standing and standing residue was 18% with BMH, 57% with SYST, 69% with BB, and 75% with FLB. Plant N uptake ranged from 53 kg N ha−1 in FLB in 2006 to 131 in SYST (BMH) in 2003 and nitrogen use efficiency, calculated using partial factor productivity formula, ranged from 0.6 to 5.8 kg bluegrass seed per kg N fertilizer. Mean NO3−–N concentrations from lysimeters 10‐cm deep were 14 mg NO3−–N L−1 in FLB, 12 mg NO3−–N L−1 in BB, and 6 mg NO3−–N L−1 in BMH treatments for years 2003–2006. Greater concentrations of NO3−–N in burn treatments were available for plant uptake or leaching compared to the BMH treatment. The data indicate that the efficacy of any residue management system will vary from year to year and impact seed production in the following year. Nitrogen availability varied across residue management systems, suggesting N fertilizer product, rate, and timing to optimize N use efficiency may also need to vary

Nitrogen fertilizer and tillage intensity affected winter wheat macronutrient uptake and utilization efficiencies

Abstract Application of N fertilizer and no‐tillage (NT) can increase winter wheat (Triticum aestivum L) production through improvements in plant available soil water and nutrient availability. However, long‐term tillage and N management interaction effects on winter wheat nutrient uptake are not well known. The objective of this study was to quantify winter wheat grain yield, macronutrient removal, and utilization responses to N fertilizer application and tillage intensity. The study was conducted in 2019 and 2020 at Hays, Kansas after 45 years of tillage and N fertility experiment. Treatments were a combination of two tillage practices (CT, conventional tillage; NT) and four rates of N (0, 45, 90, and 134 kg ha−1). Results showed a significant tillage and N fertilizer interaction effect on wheat grain yield, nutrient removal (NR) (grain‐N, ‐P, ‐K, ‐Mg; stover‐K, and total P), and nutrient concentration (stover‐K and ‐S). Two different quadratic models fit the N rate‐to‐yield relation for CT and NT with yields of 4.3 and 5.2 Mg ha−1 at agronomic optimal N rates of 119 and 199 kg N ha−1, respectively. This suggests that the N rates were not high enough to predict optimum N rate for NT in this environment. With an average yield of 3.30 Mg ha−1, wheat removed about 113 kg N ha−1, 17 kg P ha−1, 56 kg K ha−1, 7 kg Ca ha−1, 8 kg Mg ha−1, and 8 kg S ha−1, irrespective of tillage practice. Grain yields and NR were greater for CT at smaller N rates (90 kg ha−1). Findings of the study suggest that adequate N fertility (>90 kg ha−1) should be maintained to improve grain yield, nutrient uptake, and utilization efficiency in dryland NT wheat production systems

No‐tillage and nitrogen fertilization on soil chemical properties under dryland wheat–sorghum–fallow rotation

Abstract The main objective of the present study was to investigate changes in soil organic carbon (SOC), pH, as well as macro‐ and micronutrient concentrations in the top 0‐to‐5‐ and 5‐to‐15‐cm soil depths under no‐tillage (NT) and conventional tillage (CT) practices at different nitrogen (N) application rates. The soil analysis was conducted in 2019 and 2020 from CT and NT treatments from a long‐term study conducted near Hays, KS, with N fertilizer rates of 0, 45, 90, and 134 kg N ha−1. Averaged across years, SOC in the top 0‐to‐5‐cm soil depth under NT was 19% greater than that measured in CT, but SOC was not different between the two tillage practices in the 5‐to‐15‐cm depth. The SOC concentration increased by 24–25% within the top 0‐to‐5‐cm soil depth with increasing N rate from 0 to 90 or 134 kg N ha−1. Soil pH declined at rates of 0.004 and 0.007 for every kg ha−1 increase in N rate for CT and NT treatments within the 0‐to‐5‐cm soil depth. Nitrate‐N concentration under NT at the top 0–5 cm soil was 55% more than CT but ammonium‐N concentration was unaffected by tillage or N rate. Phosphorus (P), zinc (Zn), and iron (Fe) concentrations measured in the top 0–5 cm were 24, 34, and 33% greater in soils under NT compared with CT, respectively. Findings of the study suggest pH and SOC stratification in long‐term NT systems can affect soil macro‐ and micronutrient concentrations and availability in dryland crop production systems

Strategic Tillage Effects on Crop Yields, Soil Properties, and Weeds in Dryland No-Tillage Systems

Long-term no-till (NT) systems in the semiarid central Great Plains of the United States require flexible management strategies to minimize the impacts of herbicide resistant (HR) kochia (Kochia scoparia L.) and tumble windmill grass (Chloris verticillata Nutt.) as well as nutrient stratification on soil and crop productivity. This study examined strategic tillage (ST) to control HR weeds and improve crop yields in an otherwise long-term NT cropping system. Treatments were three crop rotations: (1) continuous winter wheat (Triticum aestivum L.) (WW); (2) wheat-fallow (WF); and (3) wheat-grain sorghum (Sorghum bicolor L.)-fallow (WSF); as main plots. Subplots were reduced tillage (RT), continuous NT, and ST of NT. Results showed ST and RT treatments provided significant control of HR weeds. Soil water content at wheat planting was significantly less with RT compared to NT or ST. Strategic tillage did not affect wheat or grain sorghum yields, but RT decreased sorghum yields by 15% compared to NT. Increasing cropping intensity reduced wheat yields. Strategic tillage reduced bulk density and had no effect on aggregate size distribution or mean weight diameter (MWD) compared to NT though RT reduced the proportion of large macroaggregates and MWD. Similarly, ST compared to NT had no effect on soil organic carbon (SOC) or nitrogen (N) concentrations. Soil phosphorus (P) was not different among the tillage treatments though RT increased potassium (K) concentration near the soil surface. The SOC, MWD, and micronutrient availability were greatest with WW though it had significantly lower pH and K concentration. Our results suggest ST could provide a mitigation option for HR weeds in NT systems with little impact on crop yields and soil properties