การสกัด ammonium contents in the top soil (0-5 cm) was
highly variable during the growth season but the two water
management regimes varied almost identically with a maximum
content of approx. 80 mg NH4
4 -N g1 15 วันหลังจากการหว่าน, which was 3 days after
the first urea application (Fig. 3B). Irrespective of water regime, soil
extractable ammonium content was subsequently much lower,
approx. 5-10 mg NH4
4 eN g1. Soil extractable ammonium contents
were significantly affected by sampling time (two-way ANOVA,
p < 0.001), but interaction by sampling time x water regimes was
not significant (two-way ANOVA, p ¼ 0.063).