Polymer coated urea (PCU) is a N fertilizer which, when added to moist soil, uses temperature-controlled diffusion to regulate N release in matching plant demand and mitigate environmental losses. Uncoated urea and PCU were compared for their effects on gaseous (N2O and NH3) and aqueous (NO3-) N environmental losses in cool season turfgrass over the entire PCU N-release period. Field studies were conducted on established turfgrass sites with mixtures of Kentucky bluegrass (Poa pratensis L.) and perennial ryegrass (Lolium perenne L.) in sand and loam soils. Each study compared 0 kg N ha-1 (control) to 200 kg N ha-1 applied as either urea or PCU (Duration 45CR®). Application of urea resulted in 127–476% more evolution of measured N2O into the atmosphere, whereas PCU was similar to background emission levels from the control. Compared to urea, PCU reduced NH3 emissions by 41–49% and N2O emissions by 45–73%, while improving growth and verdure compared to the control. Differences in leachate NO3- among urea, PCU and control were inconclusive. This improvement in N management to ameliorate atmospheric losses of N using PCU will contribute to conserving natural resources and mitigating environmental impacts of N fertilization in turfgrass.
Phosphorus (P) is poorly soluble in soil and has poor plant uptake efficiency. AVAIL Ò and Carbond P (CBP) are fertilizers that increase P-use efficiency (PUE) and yields on P limiting soils. The objectives of this study were to determine if mode of action for these products is related to physiological response, and to evaluate possible toxicity. AVAIL and CBP were compared to ammonium polyphosphate (APP) at pH 6 or 8 for hydroponically grown maize (Zea mays L.). Not surprisingly, biomass and P concentration increased with increasing P concentration of the solution. However, neither AVAIL nor CBP had any positive or adverse effects. These results, coupled with previous soil-based studies, show that the observed increase in PUE is not a physiological growth stimulant response, but rather the result of impacts on soil P solubility. Furthermore, these materials are not toxic when in direct contact with plant roots-even at relatively high concentrations.
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