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9 .7 SLOW-RELEASE NITROGEN FERTILIZER ON SOILS, 1976 <br /> In revegetatin work, one is often faced with the <br /> problem of nitrogen deficiency. Probably the most inexpensive <br /> so urce of N fertilizer for use at high elevations is NH4NO3 . <br /> However, if fall-applied, a good portion of the NO3 can be <br /> leached out of the root zone by snowmelt. In the past years, a <br /> number of slow-release N fertilizers have become available as <br /> well as inhibotors designed to slow down the nitrification <br /> process. <br /> Nitrate (NO3 ) since it has a negative charge is not <br /> absorbed on soil particles and if not utilized by the plants is <br /> subject to leaching . Ammonium (NH 4+) has a positive charge <br /> which is readily absorbed by the soil particles. In other <br /> words, the soil acts as a storage site for nitrogen in the <br /> ammonium form. However, with adequate moisture and the proper <br /> temperature the microbes in the soil transform ammonium (NH 4+) <br /> into nitrate (NO3 ) . <br /> N-serve is an inhibotor to the microorganism involved <br /> in the nitrification process (NH 4+ ---> NO3 ) . Ammonium ferti- <br /> lizers treated with N-serve could then be applied late in the <br /> fall . At this time of the year it is usually drier and it is <br /> easier to work with equipment and usually there is less pressure <br /> from other field work. This treated form of nitrogen will be <br /> available for the plants when they come out of dormancy in the <br /> spring . Theoretically, this practice for nitrogen application <br /> should be more efficient for the plants as well as practical for <br /> the operators. <br /> One of the most common slow-release nitrogen ferti- <br /> lizers is sulfur-coated urea. The principle involved is that <br /> urea cannot become available to plants until the sulfur coat is <br /> oxidized by microorganisms (S ----: SO 4 ) . <br /> To evaluate the most efficient N fertilizer or ferti- <br /> lizer with N-serve inhibitor for plant growth in high-altitude <br /> revegetation, consideration must be given to the following <br /> factors : <br /> 1 . Response by plant growth in early spring; <br /> 2. Residual effects; <br /> 3 . Soil testing to determine nitrate movement in the soil <br /> profile. <br /> 9-14 <br />