Nitrogen Recovery from Enhanced Efficiency Fertilizers and Urea in Intensively Managed Black Walnut (Juglans nigra) Plantations

Intensively managed forest plantations often require fertilization to maintain site fertility and to improve growth and yield over successive rotations. We applied urea-based “enhanced-efficiency fertilizers” (EEF) containing 0.5 atom% 15N at a rate of 224 kg N ha−1 to soils under mid-rotation black walnut (Juglans nigra L.) plantations to track the fate of applied 15N within aboveground ecosystem components during the 12-month period after application. Treatments included Agrotain Ultra (urea coated with a urease inhibitor), Arborite EC (urea coated with water-soluble boron and phosphate), Agrium ESN (polymer-coated urea), uncoated urea, and an unfertilized control. Agrotain Ultra and Arborite EC increased N concentrations of competing vegetation within one month after fertilization, while neither Agrium ESN nor uncoated urea had any effect on competing vegetation N concentrations during the experiment. Agrotain Ultra and Arborite EC increased δ15N values in leaves of crop trees above those of controls at one and two months after fertilization, respectively. By contrast, Agrium ESN and uncoated urea had no effect on δ15N values in leaves of crop trees until three months after fertilization. Fertilizer N recovery (FNR) varied among ecosystem components, with competing vegetation acting as a sink for applied nutrients. There were no significant differences in FNR for all the urea-based EEF products compared to uncoated urea. Agrium ESN was the only EEF that exhibited controlled-release activity in this study, with other fertilizers behaving similarly to uncoated urea.

NITROGEN RETENTION IN RAPIDLY-GROWING STEERS GIVEN UREA SUPPLEMENTED DIETS

"Shika" (indigenous, V,) and "Ngala" (introduction, V2) varieties of elephant grass (Pennisetum purpureum Schum.) field planted at 60 x 90, 60 x 60 or 60 x 30 cm spacing and fertilized at 0, 100, 200 or 400kg N/ha/yr, were examined for dry matTer (DM) yield, crude protein (CP) content, CP yield, nitrogen (N) recovery and stand persistence at Shika during the 1975 and 1976 growing seasons. The highest DM yield resulted from 60 x 30 cm spacing/400kg N combination but the 60 x 60 cm spacing (27,800 plants/ha) with 200kg N appeared optimum for yield. V produced 4.3 to 21.0t DM and V2 2.8 to 17.41 DM/ha/yr over the range of population densities and fertilizer levels investigated. DM yield per kg N applied rose with increasing population density (V, only) and decreasing N rate, the highest value of 49kg being recorded for V t. Mean herbage CP content varied from 7.0% without N to 9.7% with 400kg N/ha but the highest value of 11.0% was obtained from V2 planted at 60 x 90cm. For both grasses, N increased annual CP yield 1.2— 4.5—Fold. The highest apparent fertilizer N recovery of 76.3% occurred at 200kg N/ha while plants survived best at 60 x 60cm spacing.

Improved Root Growth by Liming Aluminum-Sensitive Rice Cultivar or Cultivating an Aluminum-Tolerant One Does Not Enhance Fertilizer Nitrogen Recovery Efficiency in an Acid Paddy Soil

The root is the main site of nitrogen (N) acquisition and aluminum (Al) toxicity. The objective of this study is to investigate whether liming and cultivation of an Al-tolerant rice (Oryza sativa L.) cultivar can improve root growth, thereby increasing N acquisition by rice plants in acid paddy soil. Two rice cultivars (‘B690’, Al-sensitive, and ‘Yugeng5’, Al-tolerant) were cultivated with 15N-labeled urea, and with or without lime in an acid paddy soil (pH 4.9) in pots. We examined root and shoot growth, soil pH, soil exchangeable Al, N uptake, 15N distribution in plant-soil system, and fertilizer N recovery efficiency. Results showed that liming improved the root growth of ‘B690’ by decreasing soil exchangeable Al concentrations, in both N-limited and N-fertilized soils. Liming enhanced the N uptake of ‘B690’ only in the absence of N fertilizer. The root weight of ‘Yugeng5’ was greater than that of ‘B690’ without lime, but the two cultivars showed similar N uptake. The fertilizer N recovery efficiency and N loss did not differ significantly between limed and non-limed conditions, or between the two rice cultivars. Thus, liming an Al-sensitive rice cultivar and cultivating an Al-tolerant one improves root growth, but does not enhance fertilizer N recovery efficiency in the present acid paddy soil.

Infuences of Rice Husk Biochar (RHB) on Rice Growth Performance and Fertilizer Nitrogen Recovery up to Maximum Tillering Stage

<p>A pot study was carried out to investigate the effects of rice husk biochar addition on rice growth performance and fertilizer nitrogen recovery. The biochar effect was studied by using ¹⁵N labelled fertilizer urea (10 atom% ¹⁵N), as isotopic tracer, until maximum tillering stage (75 days after sowing). Rice husk biochar (RHB) was applied at rates of 0, 5, 10 and 20 Mg ha^-1 and laid in randomized complete block design with four replications. The result showed that biochar application significantly improved soil chemical properties (pH, total C, total N, and available P) compared to control treatment. Biochar addition increased number of tiller and root dry matter weight up to 4% and 35%, respectively, compared to un-amended pot. Likewise, application of biochar significantly increased N, P and K uptake by 3%, 19% and 33%, respectively, as compared to the nutrient uptake from the control treatment. Biochar treatment had no significant impact on fertilizer nitrogen recovery in aboveground biomass, in the range of 41% and 42%, in comparison to the control. However, nitrogen fertilizer recovery in soil significantly increased by 47% over the control at application rate of 20 Mg ha^-1 RHB. Increased fertilizer N recovery in soil possibly reduced N losses to the environment from volatilization and denitrification processes. Total ¹⁵N fertilizer recovery also found increase at highest application of RHB biochar with an increment of 16%. In general, addition of biochar appeared to enhance crop growth performance but its effect on fertilizer N recovery in plant requires further study up to maturity of rice plant.</p>

Nitrogen Recovery and Loss from Kentucky Bluegrass Fertilized by Conventional or Enhanced-Efficiency Urea Granules

Easy handling and low unit N cost make prilled urea (46-0-0) a popular fertilizer. While incomplete recovery of granular urea applications by turfgrass is documented, field evaluations of NH3 volatilization mitigation by coatings or bioinhibitor efficiency enhancements are limited. Meanwhile, NH3 emissions reduce air quality and contribute to nutrient loading of water resources. Our objectives were to quantify 3- and 6-d ammonia emission and 9-week turfgrass recovery of unincorporated granular fertilizer application to turfgrass. In 2014 and 2015, commercial urea-N fertilizers were broadcast over a mature Kentucky bluegrass (Poa pratensis L. ‘Midnight’) lawn at 43 kg ha−1. Treatments included conventional urea and three enhanced-efficiency fertilizers; a blended fertilizer with 25% of its urea-N supplanted by polymer- and polymer-/sulfur-coated prills, or two stabilized urea fertilizers both amended by N-(n-butyl) thiophosphoric triamide (NBPT) and dicyandiamide (DCD) inhibitors. Using a 51% ‘trapping-efficiency’ flux chamber system under the field conditions described, 23.1 or 33.5% of the conventional urea-N was lost as NH3 over the respective 3- or 6-d period following application. Alternatively, dual amendment by NBPT and DCD resulted in approximately 10.3 or 19.6% NH3-N loss over the respective 3- or 6-d periods, and greater fertilizer-N recovery by the turfgrass over the 9-week experiments.