Table 5.

Concentration of ammonium nitrogen (N-NH₄) in soil solution at the depth of 50 cm (subsoil layer) in years 2013–2015 (mean values)

Fertilizer	Rate (kg ha−1)	Dose dividing	Month
			Jun (mg dm−3)	Jul (mg dm−3)	Aug (mg dm−3)	Sep (mg dm−3)	Oct (mg dm−3)	Nov (mg dm−3)
Control			0.17	0.76	0.40	0.33	0.30	0.09
Ammonium nitrate	90	1×	0.30	0.88	0.62	0.46	0.38	0.13
	90	2×	0.24	0.67	0.37	0.35	0.42	0.13
	180	1×	0.45	1.61	0.62	0.64	0.55	0.17
	180	2×	0.37	1.25	0.40	0.48	0.44	0.16
Standard urea	90	1×	0.32	0.92	0.42	0.51	0.41	0.16
	90	2×	0.23	0.66	0.38	0.44	0.33	0.14
	180	1×	0.45	1.49	0.58	0.69	0.68	0.25
	180	2×	0.37	1.29	0.45	0.55	0.58	0.20
Coated urea	90	1×	0.23	0.93	0.51	0.51	0.46	0.14
	90	2×	0.17	0.64	0.49	0.46	0.36	0.13
	180	1×	0.28	1.43	0.73	0.63	0.55	0.19
	180	2×	0.28	1.25	0.43	0.48	0.46	0.15
Average for fertilizer
Ammonium nitrate	–	–	0.34 b	1.10 a	0.50 a	0.48 a	0.45 a	0.15 a
Standard urea	–	–	0.34 b	1.09 a	0.45 a	0.55 a	0.50 a	0.19 a
Coated urea	–	–	0.24 a	1.06 a	0.54 a	0.52 a	0.46 a	0.15 a
Average for fertilizer rate
–	0	–	0.17 a	0.76 a	0.40 a	0.33 a	0.30 a	0.09 a
–	90	–	0.28 b	0.79 a	0.46 a	0.45 ab	0.37 a	0.14 b
–	180	–	0.37 c	1.39 b	0.53 a	0.58 b	0.54 b	0.19 c
Average for dose dividing
–	–	1×	0.34 a	1.21 a	0.58 a	0.57 a	0.50 a	0.17 a
–	–	2×	0.28 a	0.96 a	0.42 a	0.46 a	0.43 a	0.15 a
Average for years
2013			0.14 a	1.11 ab	0.82 b	0.92 b	0.78 b	0.12 a
2014			0.27 ab	1.39 b	0.18 a	0.11 a	0.27 a	0.13 a
2015			0.52 b	0.76 a	–	–	0.35 a	0.23 b

Letters a and b: homogeneous groups according to the Duncan test, at p < 0.05. The test was calculated separately for each month and independently for each factor (fertilizer type, fertilizer rate, dose dividing, year of experiment). The same letter indicates no difference between means for a particular factor in a particular month.