Influence of Nitrogen Fertilizer Application Methods on Rice and Changes in Soil Ammonium and Nitrate

Abstract

The study consisted of two experiments conducted concurrently at the Multiple Cropping Center (MCC)  and Mae Hia Agricultural Research Station and Training Center (MH) Faculty of Agriculture, Chiang Mai University during 2001-2002. The objectives were to examine the influence of N-fertilizer split-application (a total rate of 20 kg N rai^-1) on yield of paddy rice, Klong Laung 1 cultivar. Changes in soil NH₄⁺and NO₃ in each fertilizer treatment were also investigated.

            Results indicated that rice yields obtained from MH experimental plots which had relatively high organic matter and total N contents were not statistically different among fertilizer treatments. On the other hand, at the MCC plots with considerably low organic matter and total N, the three equal split-applications of nitrogen resulted in the highest grain yield.

             At both MH and MCC experimental plots, concentrations of NH₄⁺ and NO₃^- in surface and subsoils tended to decrease 1-3 months after rice planting for all treatments. Particularly, the NO₃^- concentration decreased rapidly t almost 0 mg N. kg^-1 within the first month (submerged conditon). Upon drainage, however, both NH₄⁺ and NO₃^- in the soil tended to increase 1-2 months after rice harvesting. Considering the very low NH₄⁺ (0.03-3.42 mg N. kg ^-1) and NO₃ (0.00-1.94 mg N. kg^-1) concentrations noted in the surface water and subsoil, the application methods and N-fertilizer rate used in the experiment were unlikely to have any adverse effect on the environment.