THE USE OF THE NITRIFICATION INHIBITOR 3, 4 DIMETHYLPYRAZOL PHOSPHATE (DMPP) ON THE GROWTH OF ROSE PLANTS CULTIVATED IN SOIL AND COCONUT FIBRE

Colombia is the largest rose producing country in Latin America. As a result, it has been researching in crop techniques to improve cut-flower quality and to be more environmentally friendly. Nitrogen fertilizers can cause environmental issues due to nitrate leaching. 3, 4-Dimethylpyrazole phosphate (DMPP) has been utilized to reduce nitrogen (N) loss from leaching or denitrification and to optimize N fertilization in crops. A greenhouse experiment was conducted to estimate the effects of DMPP on mineral N (NH₄⁺-N and NO₃^--N) in leachates during nine weeks in two substrates (Soil and coconut fibre). Eight ‘Charlotte’ rose plants grafted on ‘Natal Briar’ were used per treatment with two plants in each of four 8 L pots, fertigated with ½ Hoagland solutions (without nitrogen). Two nitrogen treatments, urea alone (UA) and urea coated with 1% DMPP (UDMPP) were established at a rate of 170 mg L^-1. Results indicated that UDMPP reduced the NO₃^--N concentration and increased the NH₄⁺-N concentration in the leachate in both substrates. N fertilizer treatments did not have any effect on physiological characteristics such as SPAD readings, Fv/Fm, leaf nitrogen concentration, and dry mass of flower stem. In conclusion, the use of DMPP-coated urea did not provide any advantages over uncoated for the production of roses, but nevertheless, these results suggest that DMPP can be an useful tool in cut-rose fertilizers programs in order to diminish nitrate losses.