Nitrogen Immobilization in Plant Growth Substrates: Clean Chip Residual, Pine Bark, and Peatmoss

Table 4

Microbial respiration in clean chip residual, pine bark and peatmoss substrates.

Substrate^z	Carbon mineralization (mg/kg)
	0 mg N	1 mg N^y	2 mg N	3 mg N	MSD N-rate^x
		0–7 days
0.48 cm CCR	2370	3236	3584	3882	113
0.95 cm CCR	1757	2593	2987	3414	154
PB	1918	2311	2367	2478	111
PM	143	94	614	258	335
MSD Substrate	84	121	284	170
		8–15 days
0.48 cm CCR	2615	2827	2888	3358	183
0.95 cm CCR	2200	2620	3105	3706	209
PB	1625	1986	1944	2021	329
PM	356	384	353	371	117
MSD Substrate	283	140	172	149
		16–30 days
0.48 cm CCR	3479	3615	3631	3436	134
0.95 cm CCR	3229	3556	3728	3714	225
PB	2254	2485	2585	2586	129
PM	751	591	578	641	166
MSD Substrate	195	139	123	126
		31–60 days
0.48 cm CCR	4133	3812	3721	3837	459
0.95 cm CCR	4082	4211	4041	3767	324
PB	2950	3173	3356	3417	190
PM	1723	1682	1581	1582	258
MSD Substrate	355	166	238	248
		Total: 0–60 days
0.48 cm CCR	12360	13414	13778	14108	609
0.95 cm CCR	11016	13110	14377	14624	799
PB	8954	10097	10313	10484	422
PM	2989	2922	2762	2781	440
MSD Substrate	668	405	662	409

^zCCR:  clean chip residual, PB:  pine bark, and PM:  sphagnum peatmoss.
^y2000 ppm stock solution of NH₄NO₃ (0, 0.5, 1.0, 1.5 mL).
^xMSD based on Waller-Duncan 𝑘 ratio 𝑡-tests (𝛼  =  0.05).