Browsing by Author "Omara, Peter"
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Item Active optical sensor measurements and weather variables for predicting winter wheat yield(Agronomy Journal, 2021) Aula, Lawrence; Omara, Peter; Nambi, Eva; Oyebiyi, Fikayo B.; Dhillon, Jagmandeep; Eickhoff, Elizabeth; Carpenter, Jonathan; Raun, William R.Accurate winter wheat (Triticum aestivum L.) grain yield prediction is vital for improving N management decisions. Currently, most N optimization algorithms use in-season estimated yield (INSEY) as a sole variable for predicting grain yield potential (YP). Although evidence suggests that this works, the yield prediction accuracy could be further improved by including other predictors in the model. The objective of this work was to evaluate INSEY, pre-plant N rate, total rainfall, and average air temperature from September to December as predictors of winter wheat YP. An 8- yr (2012–2019) data set for grain yield was obtained from Experiment 502, Lahoma, OK. The experiment was designed as a randomized complete block with four replications and N applied at 0, 45, 67, 90, and 112 kg ha–1.Weather data was obtained from the OklahomaMesonet (http://mesonet.org). The data were analyzed using R statistical computing platform. The best model was selected using least absolute shrinkage and selection operator. Root mean square error (RMSE) was obtained using k-fold cross-validation. The model selection algorithm produced the full model as the best model for yield prediction with an R2 of .79 and RMSE of 0.54 Mg ha–1. The best one-variable model – as expected – used INSEY as the predictor and had the highest RMSE of 0.72 Mg ha–1 and an R2 of .62. Mid-season YP prediction accuracy could be improved by including pre-plant N rate, mean air temperature, and total rainfall from September to December in a model already containing INSEY.Item Biochar Application in Combination with Inorganic Nitrogen Improves Maize Grain Yield, Nitrogen Uptake, and Use E ciency in Temperate Soils(Agronomy, 2020) Omara, Peter; Aula, Lawrence; Oyebiyi, Fikayo B.; Eickho, Elizabeth M.; Carpenter, Jonathan; Raun, William R.Biochar (B) has shown promise in improving crop productivity. However, its interaction with inorganic nitrogen (N) in temperate soils is not well-studied. The objective of this paper was to compare the e ect of fertilizer N-biochar-combinations (NBC) and N fertilizer (NF) on maize (Zea mays L.) grain yield, N uptake, and N use e ciency (NUE). Trials were conducted in 2018 and 2019 at Efaw and Lake Carl Blackwell (LCB) in Oklahoma, USA. A randomized complete block design with three replications and ten treatments consisting of 50, 100, and 150 kg N ha1 and 5, 10, and 15 Mg B ha1 was used. At LCB, yield, N uptake, and NUE under NBC increased by 25%, 28%, and 46%, respectively compared to NF. At Efaw, yield, N uptake, and NUE decreased under NBC by 5%, 7%, and 19%, respectively, compared to NF. Generally, results showed a significant response to NBC at 10 Mg B ha1. While results were inconsistent across locations, the significant response to NBC was evident at LCB with sandy loam soil but not Efaw with silty clay loam. Biochar application with inorganic N could improve N use and the yield of maize cultivated on sandy soils with poor physical and chemical properties.Item Biochar Applied with Inorganic Nitrogen Improves Soil Carbon, Nitrate and Ammonium Content of a Sandy Loam Temperate Soil(Nitrogen, 2022) Omara, Peter; Aula, Lawrence; Otim, Fred; Obia, Alfred; Bigatao Souza, Joao L.Biochar is suggested to improve soil properties. However, its combination with inorganic nitrogen (N) fertilizer in temperate soils is not well understood. This study compared the effect of fertilizer N-biochar-combinations (NBC) and fertilizer-N (FN) on total soil N (TSN), soil organic carbon (SOC), soil nitrate (NO3 –N), and ammonium (NH4 +–N). Soil samples were taken from experiments at Efaw and Lake Carl Blackwell (LCB), Oklahoma, USA with ten treatments consisting of three N rates (50, 100, and 150 kg N ha1) and three biochar rates (5, 10, and 15 t ha1). Results at Efaw showed greater TSN and SOC under NBC compared to FN by 3 and 21%, respectively. No percentage difference was observed for NH4 +–N while NO3 –N was lower by 7%. At LCB, TSN, SOC, NO3 –N, and NH4 +–N were higher under NBC by 5, 18, 24, and 10%, respectively, compared to FN. Whereas application of biochar improved SOC at both sites, NO3 –N and NH4 +–N were only significant at LCB site with a sandy loam soil but not at Efaw with silty clay loam. Therefore, biochar applied in combination with inorganic N can improve N availability with potential to increase crop N uptake on coarse textured soils.Item Birth Asphyxia. I. Measurement of Visual Evoked Potential (VEP) in the Healthy Fetus and Newborn Lamb(1981) Woods, James R.; Coppes, Valerie; Brooks, Daniel E.; Knowles, Peggy J.; Freeman, Marla; Parisi, Valerie; Omara, Peter; Mccarty, Garland E.The visual evoked potential (VEP) of five healthy, near-term exteriorized fetal lambs was compared with the VEP obtained from the same animals during the first hour after ventilation. Characteristics of the individual wave components and their relationship to blood pressure, heart rate, and arterial blood gas measurements concomitantly obtained were examined. ~esults show that the VEP of the healthy fetus is a stable, reproducible signal consisting of four basic components, and that the latencies (msec) and the amplitude (pV) of the individual components of the VEP are similar to those of the newborn. In two related experiments, fetal asphyxia of unknown duration was encountered during fetal exteriorization and instrumentation. In the first case, neonatal acidosis persisted despite aggressive resuscitation efforts and was accompanied by an atypical VEP. In the second case, the neonatal VEP obtained after 15 min of resuscitation was markedly depressed despite restoration of acid-base balance but gradually recovered during the remainder of the 1-hr newborn period. In conclusion, the VEP is a reproducible measure of cortical function in the healthy fetus and neonate and may reflect the acute status of cerebral function during fetal asphyxia and neonatal resuscitation.Item Characterization of the livestock production system and the potential for enhancing productivity through improved feeding in Tetugu village, Lira District, Uganda(International Livestock Research Institute (ILRI), 2015) Opio, Felix; Ongebo, Joel; Omara, PeterA feed assessment tool (FEAST) was used to assess livestock production and local feed resources in Starch Factory–Tetugu Village, Starch Factory parish, Adyel division in Lira municipality, Uganda. The study site is located within Lira municipality, 3 km north of Lira town. The assessment was carried out through a focus group discussion with 24 farmers to get an overview of the farming system and subsequently one-on-one interviews with 13 farmers (8 female, 5 male), selected from those who took part in the focus group discussion, to get quantitative information on farmers’ land holdings, crops grown on the farm, animal feed purchases, income from milk and livestock sales. The 13 farmers were selected to represent the three land endowment groups in the village (small, medium and large; with at least three from each group). The focus group discussion and individual interviews were done on 10th February 2015 and 25th-27th February 2015 respectively. The highlights of the assessment were categorized into farming systems, major income sources, management of livestock species and constraints and opportunities within the system.Item 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, WilliamCarbon 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.Item Effect of Long-term Beef Manure Application on Soil Test Phosphorus, Organic Carbon and Winter Wheat Yield(Journal of Plant Nutrition, 2017) Omara, Peter; Macnack, Natasha; Aula, Lawrence; Raun, BillIn this study, 24 years (1990-2013) of data from a long-term experiment, in Stillwater, Oklahoma (OK) were used to determine the effect of beef manure on soil test phosphorus (STP), soil organic carbon (SOC) and winter wheat (Triticum aestivum L.) yield. Beef manure was applied every four years at a rate of 269 kg nitrogen (N) ha-1 while inorganic fertilizers were applied annually at 67 kg N ha-1, 14.6 kg phosphorus (P) ha-1, and 27.8 kg potassium (K) ha-1 for N, P and K, respectively. Averaged across years, application of beef manure and inorganic P maintained STP above 38 mg kg-1 of Mehlich-3 extractable P, a level that is far beyond crop requirements. A more rapid decline in SOC was observed in the check plot compared to the manure treated plot. This study shows that application of animal manure is a viable option to maintaining SOC levels while also optimizing grain yield.Item 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, WilliamMaize 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.Item Effect of Spacing, Planting Methods and Nitrogen on Maize Grain Yield(Communications in Soil Science and Plant Analysis, 2020) Fornah, Alimamy; Aula, Lawrence; Omara, Peter; Oyebiyi, Fikayo; Dhillon, Jagmandeep; Raun, William R.Maize (Zea mays L.) production in the developing countries takes place on marginal landscapes using indigenous planting methods that conflict with appropriate row spacing (RS) and plant to plant spacing (PPS). A study was conducted to determine the effect of different RS, variable plant densities and different planting methods on maize grain yield. This study was conducted for two years at three locations in Oklahoma including Lake Carl Blackwell (Port silt loam), Efaw (Ashport silty clay loam), and Perkins (Teller sandy loam-fine-loamy). Fourteen treatments were evaluated at each location in a randomized complete block design with three replications. Treatments included two RS (0.51 m, 0.76 m), three nitrogen (N) application rates (0, 60, 120 kg N ha−1), two PPS (0.15 m, 0.30 m) and two planting methods (Greenseeder hand planter; farmers practice). Results showed an increase in grain yield by 34% in 2017 and 44% in 2018 for the narrow RS of 0.51 m compared to the 0.76 m RS. This was likely due to increased plant population at the narrow RS. This study suggests that maize producers in developing countries could use narrow RS (0.51 m) with wide PPS (0.30 m) to increase grain yields.Item Effect of winter wheat cultivar on grain yield trend under different nitrogen management(Agrosystems, Geosciences & Environment,, 2020) Aula, Lawrence; Omara, Peter; Eickhoff, Elizabeth; Oyebiyi, Fikayo; Dhillon, Jagmandeep S.; Raun, William R.In many developing countries, crop production is achieved with little or no application of fertilizer N. Understanding grain yield trends as new winter wheat cultivars (Triticum aestivum L.) are released and grown under different N management is important for crop yield improvement. This study evaluated grain yield trends of winter wheat cultivars over time in a crop production system with and without N application. Yield data was obtained from two long-term experiments; 502 (E502) and 222 (E222) between 1969 and 2018. Results showed a mean annual grain yield increase of 12 and 30 kg ha–1 yr–1 as new cultivars were released and grown under adequate N management in E222 and E502, respectively. However, without N application, yield declined annually by 2.4 kg ha–1 yr–1 in E222 and increased marginally by 0.6 kg ha–1 yr–1 in E502. Nonetheless, the yield increase or decrease was only significant for E502 at 112 kg N ha–1 (r2 = .145; p = .01) and its slope was significantly different from that of control treatment (p = .02). In both experiments, yield was significantly influenced by cultivar and N interaction (p < .01), an indication that yield changed according to the level of N applied. In general, when N was applied, grain yields were high as well. New cultivars released over time improved grain yield with adequate N management.Item Evaluation of Sorghum Emergence and Grain Yield Response to Seeding Density and Plant Spacing Attained Using the OSU Hand Planter(Communications in Soil Science and Plant Analysis, 2021) Nambi, Eva; Aula, Lawrence; Oyebiyi, Fikayo B.; Eickhoff, Elizabeth M.; Omara, Peter; Carpenter, Jonathan; Raun, William R.Plant spacing and density are important metrics in crop production because they impact the plant’s ability to utilize resources and attain full yield potential. Planting sorghum (Sorghum bicolor (L.) Moench) in a more narrow spacing brings about phytochrome-mediated responses, where plants develop narrow leaves, long stems, fewer roots, and this is linked to competition that plants develop for nutrients like nitrogen (N). The Oklahoma State University hand planter (OSU-HP) can improve plant homogeneity and midseason placement of N. However, this crop production tool alongside other agronomic practices have not been adequately evaluated for improving sorghum grain yields. The objective of this work was to evaluate the response of sorghum to planting methods, the number of seeds per hole, within row spacing, and N rate. A randomized complete block design with 13 treatments replicated 3 times was used in this study. The treatments included different combinations of 3 planting methods (John Deere [JD], OSU-HP, and stick planter [check]), 3 within-row spacings (10, 30, and 60 cm), 3 different number of seeds per hole (1, 3, and 6) and 3 N rates (0, 30 and 60 kg ha−1). Average grain yield with 3 seeds per hole was at least 18% higher than the yield range of 0.7 to 4.6 Mg ha−1 achieved with 1 or 6 seeds per hole. This study demonstrated that the production of sorghum using sound agronomic practices could improve yield.Item Improving winter wheat grain yield and nitrogen use efficiency using nitrogen application time and rate(Agrosystems, Geosciences & Environment, 2021) Aula, Lawrence; Omara, Peter; Oyebiyi, Fikayo B.; Eickhoff, Elizabeth; Carpenter, Jonathan; Nambi, Eva; Fornah, Alimamy; Raun, William R.Preplant nitrogen (N) application, which involves placing nutrients in the soil before seeding, has been an integral part of crop production systems for decades. Some producers are known to apply N at least 21 d before planting. This may increase N loss and lower grain yield. This study evaluated the effect of timing and rate of N application on winter wheat (Triticum aestivum L.) grain yield and N use efficiency (NUE). An experiment with a factorial arrangement of treatments was set up in a randomized complete block design with three replications. Treatments included four N rates (0, 45, 90, and 135 kg ha–1) with each applied 7 or 30 d before planting, and at Feekes 5 (FK5). Grain N was analyzed using LECO CN dry combustion analyzer. The difference method [Grain N from (fertilized plot – check plot)]/N applied was used to compute NUE. Nitrogen application rate significantly affected grain yield (P ≤ .01). Although the rate may be temporally and spatially variable, approximately 90 kg N ha–1 was required to obtain yields that differ markedly from the check. Midseason applied N (FK5) had similar yields to preplant applied N in two of four siteyears and significantly increased yield at one site in 2020. Out of two sites, the timing of N application had a substantial effect on NUE in both years (P ≤ 0.11). In this case, NUE was increased by as much as 9.5% for midseason applied N compared to 30 d before planting N application time.Item In-Season Application of Nitrogen and Sulfur in Winter Wheat(Agrosystems, Geosciences & Environment,, 2019) Dhillon, Jagmandeep; Dhital, Sulochana; Lynch, Tyler; Figueiredo, Bruno; Omara, Peter; Raun, W. R.Decreased atmospheric S deposition in the past 20 yr has led to increased S fertilizer consumption in winter wheat (Triticum aestivum L.). Producers often apply S without any soil test information. Experiments were conducted at Lahoma, Lake Carl Blackwell, and Perkins, OK (2011–2013) to assess the effect of N and S applied preplant and foliar on grain yield and grain N for winter wheat. In 2011–2012, urea ammonium nitrate (UAN) was applied preplant at rates of 40 and 80 kg N ha-1 additionally; UAN and urea-triazone (NSURE) were foliar-applied at rates of 10 and 20 kg N ha-1. Sulfur was foliar-applied as gypsum (CaSO4×2H2O) at 6 kg S ha-1. In 2013, trials were altered to apply 40 kg N ha-1 as UAN preplant, and 20 kg N ha-1 foliar-applied. Gypsum rates were adjusted at 0, 3, and 6 kg S ha-1 preplant, and S (MAX-IN-S) at 3 and 6 kg S ha-1 was foliar-applied. Sulfur did not increase grain yield or grain N concentration at any site. The interaction between foliar S and N and preplant S and N was not significant. Sulfur fertilizer application is less likely to benefit this region unless low levels of soil test S are identified before planting. Use of recommended soiltesting guides are encouraged. Although S applications are encouraged commercially, no response was observed in these trials, and all were on sites where soil organic carbon was low (<8.5 g kg-1), where the possibility of seeing S deficiency was greater.Item 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, WilliamNo-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.Item Iodine Agronomic Biofortification of Cabbage (Brassica oleracea var. capitata) and Cowpea (Vigna unguiculata L.) Is Effective under Farmer Field Conditions(Agronomy, 2019) Ojok, Joe; Omara, Peter; Opolot, Emmanuel; Odongo, Walter; Olum, Solomon; Gijs, Du Laing; Gellynck, Xavier; Steur, Hans De; Ongeng, DuncanIodine (I) is an essential micronutrient, which plays a critical role in human metabolism. However, its concentration is known to be low in most soils, making it deficient in crops. With most I agronomic biofortification studies conducted under controlled environments, limited information currently exists on this approach of enriching I deficient crops under farmer field conditions. Two-year field experiments were conducted in 2017 and 2018 to examine efficacy of cowpea and cabbage in the uptake of foliar applied potassium iodide (KI) and potassium iodate (KIO3), each with 0, 5, 10, and 15 kg I ha−1 under farmer field conditions. Results indicate that KI was 34% more efficient than KIO3. Iodine concentration increased with application rate. In cabbage, the lowest I concentration (8.2 mg kg−1) was registered at 5 kg I ha−1 with KIO3 while the highest was 109.1 mg kg−1 at 15 kg I ha−1 with KI. Cowpea registered the lowest I concentration of 531.5 mg kg−1 at 5 kg I ha−1 with KIO3 while the highest (5854.2 mg kg−1) was registered at 15 kg I ha−1 with KI. Therefore, cowpea and cabbage can be effectively biofortified through foliar application of both KI and KIO3 under farmer field conditions.Item 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, WilliamMethod 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.Item Nitrogen Uptake Efficiency and Total Soil Nitrogen Accumulation in Long-Term Beef Manure and Inorganic Fertilizer Application(International Journal of Agronomy, 2019) Omara, Peter; Aula, Lawrence; Raun, William R.Livestock manure is a common soil amendment for crop-livestock production systems. However, the efficiency of crop nitrogen (N) uptake from the manure-amended soil may not equate with that from inorganic N sources. +e objective of this paper was to determine the efficiency of N uptake, grain yield, and total soil nitrogen (TSN) accumulation in beef manure-amended soil compared to the inorganic N fertilizer-amended soil. Data (1990–2015) from a long-term continuous winter wheat (Triticum aestivum L.) fertility experiment at Stillwater in Oklahoma, USA, were used in this report. +ree of the six “Magruder Plot” treatments used in this study were manure, NPK plus lime (NPKL), and a check (no nutrients applied). Pre-plant N, P, and K were applied annually at 67, 14.6, and 27.8 kg·ha−1, respectively, while beef manure was applied every 4 years at 269 kgN·ha−1. +e results indicated that grain N uptake in the manure treatment (48.1 kg·ha−1) was significantly (p < 0.05) lower than that in the NPKL treatment (60.2 kg·ha−1). +is represents 20.1% efficiency of inorganic N uptake than the manure N uptake. +e average grain yield (1990–2015) from the manure and NPKL treatments was 2265.7 and 2510.5 kg·ha−1, respectively, and was not significantly different. +ere was a trend of TSN increase over the study period for both manure and NPKL treatments. +e average TSN from manure and NPKL treatments was 0.92 and 0.91 g·kg−1 soil, respectively, and was not significantly different. While no significant difference between manure and NPKL grain yield was observed, there was a significantly lower uptake efficiency of manure Ncompared to inorganic N. Furthermore, the low uptake efficiency of the manure Ncould suggest a potential for environmental pollution. Appropriate timing and application rate of manure N sources could optimize crop use efficiency and limit potential threat to the environment.Item No-tillage Improves Winter Wheat (Triticum Aestivum L.) Grain Nitrogen Use Efficiency(Communications in Soil Science and Plant Analysis,, 2019) Omara, Peter; Aula, Lawrence; Oyebiyi, Fikayo; Nambi, Eva; Dhillon, Jagmandeep S.; Carpenter, Jonathan; Raun, William RTillage practices are among the factors that affect soil quality as well as use efficiency of fertilizer nitrogen (N). Data consisting of 24-site-years from two long-term experiments 222 (E222) located in Stillwater and 502 (E502) located in Lahoma, Oklahoma were used in this study. Treatments included pre-plant N rates of 0, 45, 90, and 135 kg N ha−1 at E222 and 0, 22.5, 45, 67, 90 and 112 kg N ha−1 at E502. The objective was to evaluate the influence of no-tillage (NT) on grain N uptake and N use efficiency (NUE) of winter wheat (Triticum aestivum L.) relative to conventional tillage (CT). Generally, results indicated significantly higher grain N uptake and NUE under NT relative to CT. However, single-degree-of-freedom contrast at individual N rate indicated inconsistency in grain N uptake and NUE between experimental locations. Under both tillage practices, grain N uptake increased with N rate while NUE decreased as N rate increased. Overall, NUE and grain N uptake was 23% and 7.5% higher under NT compared to CT, respectively. Therefore, winter wheat farmers in the United States Central Great Plains currently practicing CT could improve the efficiency of the surface-applied fertilizer N and farm profitability by adopting NT.Item Review of Active Optical Sensors for Improving Winter Wheat Nitrogen Use Efficiency(Agronomy, 2020) Aula, Lawrence; Omara, Peter; Nambi, Eva; Oyebiyi, Fikayo B.; Raun, William R.Improvement of nitrogen use efficiency (NUE) via active optical sensors has gained attention in recent decades, with the focus of optimizing nitrogen (N) input while simultaneously sustaining crop yields. To the authors’ knowledge, a comprehensive review of the literature on how optical sensors have impacted winter wheat (Triticum aestivum L.) NUE and grain yield has not yet been performed. This work reviewed and documented the extent to which the use of optical sensors has impacted winter wheat NUE and yield. Two N management approaches were evaluated; optical sensor and conventional methods. The study included 26 peer-reviewed articles with data on NUE and grain yield. In articles without NUE values but in which grain N was included, the difference method was employed to compute NUE based on grain N uptake. Using optical sensors resulted in an average NUE of 42% ( 2.8% standard error). This approach improved NUE by approximately 10.4% (2.3%) when compared to the conventional method. Grain yield was similar for both approaches of N management. Optical sensors could save as much as 53 ( 16) kg N ha1. This gain alone may not be adequate for increased adoption, and further refinement of the optical sensor robustness, possibly by including weather variables alongside sound agronomic management practices, may be necessary.Item Unpredictable Nature of Environment on Nitrogen Supply and Demand(Agronomy Journal, 2019) Raun, William R.; Dhillon, Jagmandeep; Aula, Lawrence; Eickhoff, Elizabeth; Weymeyer, Gwen; Figueirdeo, Bruno; Lynch, Tyler; Omara, Peter; Nambi, Eva; Oyebiyi, Fikayo; Fornah, AlimamyThe second law of thermodynamics states that entropy or randomness in a given system will increase with time. This is shown in science, where more and more biological processes have been found to be independent. Contemporary work has delineated the independence of yield potential (YP0) and nitrogen (N) response in cereal crop production. Each year, residual N in the soil following crop harvest is different. Yield levels change radically from year to year, a product of an ever-changing and unpredictable/ random environment. The contribution of residual soil N for next years’ growing crop randomly influences N response or the response index (RI). Consistent with the second law of thermodynamics, where it is understood that entropy increases with time and is irreversible, biological systems are expected to become increasingly random with time. Consequently, a range of different biological parameters will influence YP0 and RI in an unrelated manner. The unpredictable nature that environment has on N demand, and the unpredictable nature that environment has on final grain yield, dictate the need for independent estimation of multiple random variables that will be used in mid-season biological algorithms of the future.