Browsing by Subject "Urea"

Now showing 1 - 3 of 3
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    Degradable intake protein supplementation through the inclusion of urea in finishing diets containing distillers grains: effects on feedlot cattle performance, ruminal fermentation, and feed digestibility
    (2014-05) Ceconi, Irene
    Degradable intake protein (DIP) represents the proportion of protein that is potentially fermented in the rumen. Ruminal DIP balance is calculated by the difference between DIP supply and requirements. The former is a function of dry matter intake and dietary DIP, and represents nitrogen (N) available for synthesis of microbial crude protein (MCP), which is used as a measurement of microbial growth or production of new microbial cells. Synthesis of MCP basically requires ammonia-N (NH3-N), carbon skeletons, and energy. While the last two are mainly derived from fermentation of dietary carbohydrates, dietary N represents the main NH3-N source. Consequently, DIP requirements represent rumen-degradable N needs for MCP synthesis, and are a function of available fermentable carbohydrates. High dietary inclusion of grain as well as more extensive grain processing methods can result in increased ruminal availability of rapidly-fermentable carbohydrates, which in turn may result in increased DIP requirements. In addition, corn-based diets may not supply adequate amounts of DIP because corn protein is considered to be approximately 60% undegradable. Despite great protein content and because of great undegradable protein concentration, small to moderate dietary inclusion of corn distillers grains (DG) may also result in DIP deficit. Experiments 1 and 2 described in Chapter 2 evaluated the effect of adding urea, a highly rumen-degradable N source, to a high-concentrate, moderate-DG-containing diet on feedlot cattle performance, ruminal fermentation, and feed digestibility. Results from both experiments indicate that due to a DIP deficit generated by the un-supplemented diet, the addition of urea resulted in enhanced ruminal fermentation and feed digestibility, and consequently improved animal performance. Because rates of degradation of carbohydrates and conventional urea do not match, beneficial effects may arise from the use of slow-release urea (SRU) sources over conventional urea when added to DIP-deficient diets. Therefore, experiments 1 and 2 described in Chapter 3 evaluated the effect of increasing DIP concentration through the inclusion of one of two SRU sources in comparison with the inclusion of conventional urea in DG-containing feedlot diets on ruminal fermentation and feed digestibility. Likely due to lack of DIP deficit with the un-supplemented diet, results from these experiments do not demonstrate potential beneficial effects of SRU sources over conventional urea. Several confluent factors are discussed that may explain lack of need of urea supplementation in Chapter 3 experiments. Because previous studies have demonstrated improved ruminal fermentation, feed digestibility, and animal performance when supplementing conventional urea to rapidly-fermentable, moderate-DG-containing diets, more research is warranted to evaluate the use of SRU in diets for which a DIP deficit is expressed.
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    Improving Maize Production and Ground-Water Quality through Nitrogen Management in Minnesota’s Irrigated Coarse-Textured Soils
    (2016-03) Struffert, Anne
    Elevated groundwater nitrate (NO3-N) concentrations in irrigated sandy soils under corn (Zea mays L.) production in the Midwest is of increasing concern, and has prompted the need to identify new or enhanced nitrogen (N) management practices in these areas. The objective of this study was to evaluate agricultural technologies that may improve N management for profitable corn production and mitigate negative effects of NO3-N in groundwater. From 2011 to 2014 corn was grown at two sites in Minnesota on sandy soils, Dakota County, MN with a continuous corn (CC) rotation and Pope County, MN with a CC, corn after soybeans (CSB), and soybean after corn (SbC) rotations. Twelve treatments were applied including urea broadcast at rates of 0, 45, 90, 135, 180, 225, 270, and 315 kg N ha-1 as a split application, half at pre-plant and half at the V4 development stage, pre-plant Super U at 180 kg N ha-1, and pre-plant ESN at 180 and 225 kg N ha-1. Canopy sensing with SPAD, GreenSeeker, and Crop Circle was done at V8 and V12 and NO3-N basal stalk measurements at R6 development stage. Soil water NO3-N samples were collected weekly throughout the growing season below the rooting zone using suction lysimeters. The mean Maximum Return to N (MRTN) was 231 kg ha-1 and produced a mean-yield increase above the unfertilized check of 6.5 Mg ha-1. Canopy sensors and plant measurements provided limited utility and generally under-predicted N needs. Nitrogen use efficiency and yields were increased with split-applied urea compared to all other pre-plant sources at 180 kg N ha-1, but no reduction in NO3-N leaching occurred. Season-long NO3-N concentrations ranged from 10 to 46 mg L-1 and overall annual loss was 27 to 41 kg NO3-N ha-1. Reducing N rate below the MRTN substantially reduced yield without reducing NO3-N leaching losses.
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    Time And Rate Of Nitrogen Fertilization Influence Maize Nitrogen Use Efficiency And Soil Enzyme Activity
    (2018-09) Davies, Benjamin
    Experiments were conducted from 2014 to 2016 comparing single (fall and spring) and split applications of differing nitrogen (N) rates for maize (Zea mays L.) on an irrigated Hubbard-Mosford loamy sand complex at Becker, a non-irrigated Normania loam soil at Lamberton, and a non-irrigated Nicollet clay loam soil at Waseca, MN. Fall and spring treatments were applied at recommended and 125% of recommended rates based on University of Minnesota guidelines for the different locations. Split-application treatments consisted of Sp, a two-way split (one-half of the N applied before planti and one-half applied at the six-leaf collar stage of maize phenological development (V6) and TSp, a three-way split (one-third of the N applied pre-plant, one-third at the V6 stage, and one-third at the silking stage of maize phenological development (R1) stage. Nitrogen rates varied by location and were based on University of Minnesota guidelines. All sites were planted to soybean [Glycine max L. (Merr.)] in 2013 and to maize in 2014 to 2016. At Becker, applying N fertilizer at the recommended rate as a three-way split improved maize grain and biomass yield, maize nutrient uptake, and nitrogen use efficiency (NUE). At Lamberton, grain yield, nutrient uptake, and NUE parameters did not differ among treatments applied at recommended rates, regardless of application time. At Waseca, applying the recommended N rate as either a two- or three-way split improved grain yield and NUE compared with fall or pre-plant application, while recommended N rates maximized nutrient uptake. Soil enzyme activity fluctuated across the growing season and decreased over time, particularly in the coarse-textured soils at Becker. Although microbial activity declined annually, there was no significant change in glucosidase activity. There was a decline in acid phosphatase activity in coarse- but not finer-textured soils. At Becker, applying N fertilizer as a three-way split increased sulfatase activity compared with applying N fertilizer in the fall or pre-plant. Enhanced understanding of how site-specific soil and weather characteristics influence these responses could increase maize yield and nutrient uptake while reducing the potential for nitrogen loss to the environment.