In general, T3 reduced N use efficiency. The less availability of N observed for this treatment was probably due to fixation of NH3 by HA, during fertilizer formulation or in soil. HA has the ability to fix significant amount of NH3 at high pH (>7). Based on a previous study, rapid increase of pH was noted for T3 (pH 1.89 (LHA) to pH 9.04 (LHA + urea)). At pH of 9.04, N could be in NH3 form and could be fixed by HA. Thus, it was consistent that the HA can affect N contents in plants and its uptake (Visser, 1985). Even though Tan (2003) reported that the presence of HA could increase the uptake of N by plant significantly, it was the contrary in this study. The concentration of N and its uptake also partly explains this observation. This was because N uptake relates to N use efficiency (Moll et al., 1981).