Ammonia (NH 3 ) volatilization from surface-applied N fertilizers containing urea can be substantial if environmental conditions are favorable. Physically coating urea with sulfate salts and urease inhibitor may reduce NH 3 volatilization and supply plant available S. Th e objectives of this study were to quantify in vitro N loss from surface-applied urea; and measure the rate and total N volatilization loss from urea coated with calcium sulfate, potassium sulfate, alone and in combination with the urease inhibitor, N-(n-butyl) thiophosphoric triamide (NBPT). Six trials, lasting 14 d, were conducted using a laboratory system at 26°C, 1.00 L min -1 air fl ow, 44.6 mg N kg -1 air-dried soil, and 100 mL of 0.02 M phosphoric acid to recover volatilized NH 3 . Cumulative NH 3 loss ranged from 33.9 to 37.2% of the applied N in all trials. Initial NH 3 volatilization losses were delayed by calcium and potassium sulfate coatings alone. Th e inhibitor NBPT reduced cumulative NH 3 losses to 17.9 to 24.7% of applied N and delayed NH 3 volatilization for 96 h aft er N application when applied at the 0.08% w/w application rate in trials I to IV. In trials V and VI, applying NBPT at 0.02% w/w reduced cumulative NH 3 volatilization from 35.6 and 35.1% to 25.4 and 24.1%, respectively. In both trials, no diff erence in cumulative NH 3 loss was observed when NBPT rates exceeded 0.04%. Th e inhibitor NBPT had the greatest infl uence on NH 3 volatilization losses in these studies, though the K 2 SO 4 coated urea also reduced NH 3 volatilization and supplies a small amount of S for crop growth.

No abstract

The design of laboratory systems for studying ammonia (NH3) released from fertilizers varies widely, and few designs have been tested to determine the accuracy and precision in measuring NH3 loss. A standard volatilization system design is needed for reliable and comparable studies of NH3 volatilization from N fertilizer. The objectives of this study are: (i) to describe the design of a system capable of controlling air flow rate and temperature for laboratory measurement of NH3 volatilized from N fertilizers; and (ii) assess the system's efficiency and variation in recovering NH3 lost from NH4Cl applied to an alkaline sand media. The system is comprised of individual chambers for soil and fertilizer, where temperature can be varied from room temperature to ∼32°C; humidity is maintained near saturation, air flow rate can be varied, and acid traps are used to capture volatilized NH3. Two initial trials (I and II) were conducted at an N rate of 90 kg N ha−1 using air flow rates of 2.00 and 1.00 L min−1 and trapping acid volumes of 50 and 100 mL, respectively. A third trial was conducted at 30°C. A fourth trial (IV) was performed using a range of N application rates (25–250 kg N ha−1). The system recovered 89.3 to 97.1% of the N applied over all four trials and provided accurate and repeatable results under the conditions tested. Rapid, precise comparisons of NH3 volatilization losses from N fertilizers under laboratory conditions can be made with this system.

Urea has become the dominant synthetic nitrogen fertilizer used worldwide; however, surface application of urea based fertilizers can lead to significant volatilization losses. The objectives of this research were: (i) to compare the effect of urea with and without the urease inhibitor N‐(n‐butyl) thiophosphoric triamide (NBPT) on corn ear leaf N concentration and grain yield; and (ii) to compare the effect of sulfate salts as coatings with and without NBPT on N concentration in corn ear leaves and corn grain yield in field studies. Urea and Arborite Ag, NBPT, were applied at four N rates: 50, 100, 150, and 200 lb/N acre; and the other seven coated urea treatments were applied at 100 lb N/acre at V5‐V7. The N concentration in corn ear leaves was significantly increased using Arborite Ag at 5 out the 10 locations during the study at α = 0.1. Regression analyses to predict N concentration in corn ear leaves and grain yield with N rates were significant for all 10 locations for N in corn ear leaves and 9 out of 10 for grain yield; however, the analyses indicate the N rate used to compare coated treatments (100 lb N/acre) was too high to detect treatment differences.

HighlightsPhosphoric acid (PA) increased water-soluble phosphorus (WSP) from 0.31 to 47.4 g P kg-1 in poultry litter ash (PLA).Ideal granule size was identified at 29% acidulation (14.5 g acid to 50 g PLA) with granules averaging 3.14 mm.Bulk fertilizer production needed 32% PA addition, and adequate mixing equipment is important for PA efficiency.Granule size and strength were adequate as compared to industry standards and commercial fertilizers.Abstract. Manure-to-energy systems effectively recycle poultry litter (PL) into poultry litter ash (PLA) that densifies and concentrates the phosphorus (P) content by a factor of 4 to 10. However, high conversion temperatures reduce nutrient solubility and produce small particulate materials. To redistribute manure nutrients beyond the original production location by improving the physical and chemical characteristics of PLA, the objectives of this research were to: (1) determine the phosphoric acid (H3PO4) acidifying effect on water-soluble P (WSP), measurable total P (TP), granulation point, and granule size and (2) conduct large-scale granulated poultry litter ash bulk (GPLA-B) granulation to determine the larger-scale formulations and granule physical characteristics produced. We measured bulk density, force and friction resistance, and granule size as compared to industry-standard triple superphosphate (TSP). Acidulation experiments were arranged in a completely randomized design with four replications per H3PO4 acidulation percentage. Increasing acidulation percentages from 0% to 50% H3PO4 (laboratory-grade white phosphoric acid) increased measurable TP from 50.63 to 116.90 g kg-1 and WSP from 0.31 to 47.4 g P kg-1 (LSD0.05 10.13 and 2.65 g P kg-1, respectively). Acidulation dose response relationships created simple linear regression equations to predict changes in measurable TP and WSP, pH, and exothermic reaction temperature, which all increased with acidulation. The loose (1.01 g cm-3) and packed (1.03 g cm3) bulk densities of GPLA-B were significantly less than those of TSP (1.14 and 1.30 g cm3, respectively) (LSD0.05 = 0.03 and 0.02 g cm-3). Compared to TSP particles (2.86 mm), GPLA particles (3.73 mm) were significantly larger (LSD0.05 = 0.61 mm); however, the force resistance of GPLA (4.53 kgf) was significantly less than that of TSP (5.95 kgf) (LSD0.05 = 0.61 kgf). Results showed that the physical characteristics of GPLA met industry standards and validated the adaptability of GPLA as an alternative P source. Furthermore, GPLA has higher elemental analysis, greater solubility, and improved form, which addresses the undesirable characteristics of ungranulated PLA and supports the use of GPLA for fertilizer and nutrient distribution. Keywords: Acidulation, Fertilizer, Granulation, Phosphorus, Poultry litter ash.