3.2.1. Seasonal changes of available N, non-exchangeable NH4
+ and pH
3.2.1.1. Seasonal changes of available N. Available soil N varied
significantly with years of study and date of sampling (p < 0.001)
(Table 3). Higher values of soil available N were observed in
2012 compared with 2011. At all sampling dates, before and after N
fertilization, NH4
+ was the dominant inorganic N form. The total
available soil N content (NH4
+ + NO3
) significantly rose after the
basal dressing, from 5.3 to 10.2 mg N kg1 at
first sampling after
this fertilization under aerobic conditions (Table 2, Fig. 1). A
significant decrease in total available N was observed after
flooding
till the topdressing (11 and 10 July, respectively in 2011 and 2012),
in particular in NH4
+ form. Immediately after topdressing and
maintaining the
flooding condition, the total available N
significantly increased from 4.9 to 5.8 mg N kg1, but decreased
thereafter till the maturity. Overall, the total available N