FATE AND EFFICIENCY OF N-FERTILIZERS APPLIED TO PEARL-MILLET IN NIGER

Field studies were conducted in Niger using 15N-labeled fertilizers to assess the fate and efficiency of fertilizer N in pearl millet (Pennisetum glaucum [L.] R.Br.) production. Total plant uptake of fertilizer N was low in all cases (20%-37%), and losses were severe (25%-53%). The majority of N remaining in the soil was found in the 0- to 15-cm layer though some enrichment at lower depths was found when the N fertilizer was calcium ammonium nitrate (CAN). In a comparison of urea placement methods (band, broadcast, or point placement), no significant differences in 15N uptake or yield were noted though point placement did exacerbate 15N loss. The mechanism of N loss is believed to have been ammonia volatilization. Yields were similar whether urea or CAN was used, but 15N uptake from CAN was higher. A statistical model was developed relating millet yield and N response to midseason rainfall. In drought years, no N response was found, whereas in years of good rainfall a response was found of 15 kg grain for each kilogram of N applied (at 30 kg N ha-1 rate). © 1990 Kluwer Academic Publishers.