Browsing by Author "Raun, William"

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    Effect of Fertilizer Nitrogen (N) on Soil Organic Carbon, Total N and Soil Ph in Long-Term Continuous Winter Wheat (Triticum Aestivum L.)
    (Communications in Soil Science and Plant Analysis, 2016) Aula, Lawrence; Macnack, Natasha; Omara, Peter; Mullock, Jeremiah; Raun, William
    Carbon sequestration via sound agronomic practices can assist in combatting global warming. Three long-term experiments (Experiment 502, Experiment 222, and The Magruder Plots) were used to evaluate the effect of fertilizer nitrogen (N) application on soil organic carbon (SOC), total nitrogen (TN) and pH in continuous winter wheat. Soil samples (0-15 cm) were obtained after harvest in 2014, analyzed and compared to soil test results from these same experiments in 1993. Soil pH decreased with increasing N fertilization, and more so at high rates. Nitrogen application significantly increased TN in Experiment 502 from 1993 to 2014, and TN tended to be high at high N rates. Fertilizer N significantly increased SOC, especially when N rates exceeded 90 kg ha-1. The highest SOC (13.1 g kg-1) occurred when 134 kg N ha-1 was applied annually. Long-term N application at high rates increased TN and SOC in the surface soil.
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    Effect of Seed Distribution and Population on Maize (Zea mays L.) Grain Yield
    (International Journal of Agronomy, 2014) Chim, Bee Khim; Omara, Peter; Macnack, Natasha; Mullock, Jeremiah; Dhital, Sulochana; Raun, William
    Maize planting is normally accomplished by hand in the developing world where two or more seeds are placed per hill with a heterogeneous plant spacing and density. To understand the interaction between seed distribution and distance between hills, experiments were established in 2012 and 2013 at Lake Carl Blackwell (LCB) and EfawAgronomy Research Stations, near Stillwater, OK. A randomized complete block design was used with three replications and 9 treatments and a factorial treatment structure of 1, 2, and 3 seeds per hill using interrow spacing of 0.16, 0.32, and 0.48m. Data for normalized difference vegetation index (NDVI), intercepted photosynthetically active radiation (IPAR), grain yield, and grain N uptake were collected. Results showed that, on average, NDVI and IPAR increased with number of seeds per hill and decreased with increasing plant spacing. In three of four site-years, planting 1 or 2 seeds per hill, 0.16m apart, increased grain yield and N uptake. Over sites, planting 1 seed, every 0.16m, increased yields by an average of 1.15Mgha−1 (range: 0.33 to 2.46Mg ha−1) when compared to the farmer practice of placing 2 to 3 seeds per hill, every 0.48m.
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    Influence of No-Tillage on Soil Organic Carbon, Total Soil Nitrogen, and Winter Wheat (Triticum aestivum L.) Grain Yield
    (International Journal of Agronomy, 2019) Omara, Peter; Aula, Lawrence; Eickhoff, Elizabeth M.; Dhillon, Jagmandeep S.; Lynch, Tyler; Wehmeyer, Gwendolyn B.; Raun, William
    No-tillage (NT) can improve soil properties and crop yield. However, there are contrasting reports on its benefits compared to conventional tillage (CT). Dataset (2003–2018) from long-term continuous winter wheat (Triticum aestivum L.) experiments 222 (E222) at Stillwater and 502 (E502) at Lahoma in Oklahoma, USA, established in 1969 and 1970, respectively, was used. Both experiments were managed under CTuntil 2010 and changed to NT in 2011. In each tillage system, treatments included nitrogen (N) rates at E222 (0, 45, 90, and 135 kg·N·ha− 1) and E502 (0, 22.5, 45, 67, 90, and 112 kg·N·ha− 1). (e objective was to determine the change in wheat grain yield, soil organic carbon (SOC), and total soil nitrogen (TSN) associated with the change to NT. Grain yield was recorded, and postharvest soil samples taken from 0–15 cm were analyzed for TSN and SOC. Average TSN and SOC under NT were significantly above those under CT at both locations while grain yield differences were inconsistent. Under both tillage systems, grain yield, TSN, and SOC increased with N rates. At E222, grain yield, TSN, and SOC under NT were 23%, 17%, and 29%, respectively, more than recorded under CT. At E502, grain yield was lower under NT than CT by 14% while TSN and SOC were higher by 11% and 13%, respectively. Averaged over experimental locations, wheat grain yield, TSN, and SOC were 5%, 14%, and 21%, respectively, higher under NTcompared to CT. (erefore, NTpositively influenced grain yield, TSN, and SOC and is likely a sustainable long-term strategy for improving soil quality and crop productivity in a continuous monocropping system.
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    Nitrogen management impact on winter wheat grain yield and estimated plant nitrogen loss
    (Agronomy Journal, 2020) Dhillon, Jagmandeep; Eickhoff, Elizabeth; Aula, Lawrence; Omara, Peter; Weymeyer, Gwen; Nambi, Eva; Oyebiyi, Fikayo; Carpenter, Tyler; Raun, William
    Method of N application in winter wheat (Triticum aestivum L.) and its impact on estimated plant N loss has not been extensively evaluated. The effects of the pre-plant N application method, topdress N application method, and their interactions on grain yield, grain protein concentration (GPC), nitrogen fertilizer recovery use efficiency (NFUE), and gaseous N loss was investigated. The trials were set up in an incomplete factorial within a randomized complete block design and replicated three times for 5 site-years. Data collection included normalized difference vegetation index (NDVI), grain yield, and forage and grainNconcentration. TheNDVI before and after 90 growing degree days (GDD) were correlated with final grain yield, grain N uptake, GPC, and NFUE. At Efaw location, NDVI after 90 GDDs accounted for 58% of variation in grain yield and 51% variation in grain N uptake. However, NDVI was found to be a poor indicator of both GPC and NFUE. Grain yield was not affected by the method and timing of N application at Efaw. Alternatively, at Perkins, topdress applications resulted in higher yields. The GPC and NFUE were improved with the topdress applications. Generally, topdress application enhanced GPC and NFUE without decreasing the final grain yield. The difference method used in calculating gaseous N loss did not always reveal similar results, and estimated plant N loss was variable by site-year, and depended on daily fluctuations in the environment.
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    Variability in Winter Wheat (Triticum aestivum L.) Grain Yield Response to Nitrogen Fertilization in Long-Term Experiments
    (Communications in Soil Science and Plant Analysis, 2020) Omara, Peter; Aula, Lawrence; Dhillon, Jagmandeep S.; Oyebiyi, Fikayo; Eickhoff, Elizabeth M.; Nambi, Eva; Fornah, Alimamy; Carpenter, Jonathan; Raun, William
    Crop nitrogen (N) use is always affected by the variability in production environment. Dataset (2001 to 2014) from long-term winter wheat (Triticum aestivum L.) experiments at Lahoma and Stillwater, Oklahoma was used. Both experiments have a randomized complete block design with four replications, and fertilizer N was applied as urea pre-plant. Responsiveness of grain yield to maximum fertilizer N rate (112 kg ha−1 – Lahoma; 135 kg ha−1 – Stillwater) was compared with that from check plot (0 kg ha−1). The objective was to determine the relative influence of environment, management, and variety on winter wheat grain yield. The combined analysis of variance indicated that the main effect of year, treatment, location, and variety accounted for 29.3%, 21.2%, 3.1%, and 22.6%, respectively of the variance terms. Over the study period, the nonresponsiveness of winter wheat to fertilizer N accounted for 29% and 23% of grain yield at Lahoma and Stillwater, respectively where yield at maximum N rate did not significantly differ from check plot. This highlights the importance of random changes in a crop production environment and its influence in dictating the response to applied N fertilizer. Nitrogen fertilizer losses could be reduced by adopting in-season variable N application techniques.