SHORT-TERM IMMOBILIZATION OF FERTILIZER NITROGEN AT THE SURFACE OF NO-TILL AND PLOWED SOILS

Immobilization of (NH4)2SO4 in no-till and conventionally tilled soils was monitored after application of 15N enriched material to the surface of 20-cm diameter plots on 3 soil types. Soils were collected periodically up to 35 d [days] and 15N in organic and inorganic fractions was measured. On all 3 soils there was more immobilization in no-till. After 35 d, the percentage of fertilizer applied that was immobilized was 21 and 11 on Maury silt loam, 13 and 6 on Tilsit silt loam, and 24 and 15 on Cavode silt loam for no-till and conventional tillage, respectively. There were no consistent trends or statistically significant differences between tillage treatments with regard to total N recovery (organic plus inorganic). The increased potential for immobilization of N at the surface of no-till soils may significantly reduce crop recovery of fertilizer N.