Fresh and Composted Paper Sludges Sustain Soil Productivity

Table 3

Residual effects of applications of fresh and composted paper sludges, and N fertilizer on soil bulk density, nitrogen and carbon contents, C/N ratio, and C (Mg ha^-1) at 0–10-cm soil layer in 2004.

Treatments	Bulk density	Total N	C	C/N	C
	g cm^-3	g kg^-1	g kg^-1		Mg ha^-1
Frequency (single application)
Control	1.44	1.38	16.8	12	40.7
N fertilizer (160 kg N ha^-1)	1.49	1.30	15.6	12	39.6
FDS	1.44	1.50	20.7	14	50.3
CDS	1.42	1.50	19.2	13	46.0
FDS + 120 kg N ha^-1	1.47	1.42	19.0	13	47.4
CDS + 120 kg N ha^-1	1.44	1.58	21.2	13	51.6
Frequency (triple application)
Control	1.50	1.36	16.5	12	42.3
N fertilizer (160 kg N ha^-1)	1.49	1.31	15.9	12	40.2
FDS	1.39	1.59	21.9	14	51.4
CDS	1.47	1.43	19.0	13	47.4
FDS + 120 kg N ha^-1	1.43	1.43	19.2	13	46.4
CDS + 120 kg N ha^-1	1.44	1.52	20.0	13	49.0
ANOVA F values
Treatments	1.80	11.82^∗∗	16.57^∗∗	13.15^∗∗	16.08^∗∗
Frequency	0.04	0.05	0.00	0.30	0.04
Treatments × Frequency	1.58	1.05	0.55	0.40	0.53
Contrasts
(1) Control versus others	1.11	7.04^∗	18.06^∗∗	24.91^∗∗	19.67^∗∗
(2) N fert. versus FDS and CDS	5.64^∗	38.84^∗∗	51.44^∗∗	30.61^∗∗	49.50^∗∗
(3) FDS versus CDS	0.48	0.65	0.39	7.08^∗	0.12
(4) FDS^‡ versus FDSN^§	1.77	8.01^∗	8.62^∗∗	3.09	6.30^∗
(5) CDS^{ versus CDSN^#	0.00	4.56^∗	4.02	0.06	4.94^∗

∗. ^∗∗=.05 and  .01 probability levels of statistically significant difference, respectively.
^‡FDS, ^§FDSN: fresh paper sludges alone or with N fertilizer, respectively.
^{CDS, ^#CDSN: composted paper sludges alone or with N fertilizer, respectively.