TURFGRASS RESPONSE TO FOLIAR APPLIED NITROGEN

Concern exists within the lawn care industry as to the merits of foliar applied nitrogen. Efficiency of foliar N uptake is influenced by foliar burn, N uptake, and volatilization loss. Turfgrass quality for turfs receiving foliar N fertilization is dependent upon nitrogen rate, nitrogen source, and water application rate. With these aspects in mind, field and controlled environment studies were conducted to evaluate 'Park' Kentucky bluegrass (Poa pratensis L.) response to liquid applied nitrogen.; In field studies, unacceptable periods of turfgrass quality occurred with liquid applications of ammonium nitrate as a result of foliar burn. Best overall quality occurred with granular applications of ammonium nitrate and urea. Comparisons between urea and formolene demonstrated that foliar burn was higher with urea and was intensified by increased N rate and reduced water application rate. Turfgrass color and quality were similar for urea and formolene after burn had dissipated. Seasonal effects of foliar applied urea indicated peak periods of turfgrass growth and N uptake in spring and fall which was intensified with increased N rate and following N applications. Maximum nitrogen loss from clipping removal was 60%. Over 30% of foliar applied urea was lost through ammonia volatilization over four days. Nitrogen uptake was rapid with 14% derived from foliar applied urea nine hours after treatment. Turfgrass response under controlled environment indicated that maximum foliar N uptake occurred 24 hours after foliar urea was applied. Pattern of N uptake varied between turfgrasses with N recoveries ranging from 31 to 61%.; Results of these studies provided information on N efficiency of liquid applied nitrogen that was not previously available. Information of this nature will be beneficial to lawn care services in developing and maintaining acceptable turf.