Effect of different application rates of organic fertilizer on soil enzyme activity and microbial population

Figures & data

Table 1 Major chemical properties of the composts used in the experiment

Item^†	Compost A	Compost B	Compost C	Compost D
pH (1:5)	7.17	5.50	7.29	8.00
EC^‡ (dS m^−1)	12.6	18.7	4.6	11.6
Organic matter (g kg^−1)	715	521	736	469
Total nitrogen (g kg^−1)	52.4	26.0	24.3	21.8
Organic N (g kg^−1)	50.7	19.8	22.9	21.3
Insoluble N (g kg^−1)	34.3	14.6	19.3	18.8
NO^− 3-N(g kg^−1)	0.05	0.05	0.03	0.45
NH^+ 4-N(g kg^−1)	1.63	6.15	1.34	0.10
Total P (g kg^−1)	8.93	8.69	6.41	3.55
Total K (g kg^−1)	12.0	19.3	9.8	30.9
Total Ca (g kg^−1)	54.6	18.4	43.9	24.3
Total Mg (g kg^−1)	17.6	10.1	10.6	6.0
Total Cu (mg kg^−1)	18.8	12.6	15.1	16.0
C/N	7.9	11.6	17.5	12.5
Moisture content (%)	32.2	25.8	30.5	38.5
^†On a dry weight basis except for the moisture content.
^‡EC, electric conductivity (1:5).

Table 2 Effect of different application rates of compost on some selected chemical properties of the soil

Treatment	pH (1:1)	EC (dS m^−1)	OM (g kg^−1)	Total N (g kg^−1)	NH^+ 4-N (mg kg^−1)	NO^− 3-N (mg kg^−1)	P^c (mg kg^−1)	K^d (mg kg^−1)	Ca (mg kg^−1)	Mg (mg kg^−1)
CF	7.04 d^†	3.51 b	26.6 e	1.59 cd	29.2 a	51 c	167 d	114 d	1681 d	239 d
CK	7.83 a	1.56 d	25.1 e	152 d	26.3 ab	17 c	135 e	74 d	1634 d	251 d
Rate 1	7.77 ab	3.15 b	31.4 d	1.94 cd	26.1 ab	54 c	168 d	141 cd	2108 c	333 c
Rate 2	7.64 ab	3.53 b	38.0 c	1.89 cd	18.7 bc	89 bc	209 c	240 cd	2533 b	382 b
Rate 3	7.54 bc	4.58 ab	46.1 b	2.39 b	13.5 cd	159 ab	251 b	411 b	3063 a	482 a
Rate 4	7.39 c	5.17 a	53.0 a	3.13 a	6.10 d	200 a	294 a	613 a	2958 a	472 a
^†Within columns, means followed by the same letter are not significantly different (P = 0.05) using Duncan's multiple range test. CF, chemical fertilizer; CK, no application of fertilizer; EC, electric conductivity; OM, organic matter; P, Bray-1 extractable P; K, Mehlich-III extractable K; Ca, Mehlich-III extractable Ca; Mg, Mehlich-III extractable Mg.

Table 3 Effect of different application rates of compost on microbial populations of the soils

Treatment	Bacteria (10^7 c.f.u. g^−1)	Actinomycetes (10^7 c.f.u. g^−1)	Fungi (10^4 c.f.u. g^−1)
CF	3.24 d^†	1.17 d	3.39 c
CK	3.72 cd	1.32 d	3.80 bc
Rate 1	4.47 cd	1.82 c	4.68 abc
Rate 2	4.68 bc	2.00 bc	5.25 ab
Rate 3	5.75 ab	2.24 ab	5.62 a
Rate 4	6.92 a	2.40 a	5.75 a
^†Within columns, means followed by the same letter are not significantly different (P = 0.05) using Duncan's multiple range test. CF, chemical fertilizer; CK, no application of fertilizer.

Table 4 Effect of different application rates of compost on some microbial properties of the soil

Treatment	Microbial C (µg C g^−1)	Ninhydrin-N (µg Leu g^−1)	CO2 respiration rate (µg CO2 g^−1 h^−1)	Nitrification rate (µg NO2 g^−1 h^−1)
CF	301 d^†	6.32 bc	1.65 c	0.594 d
CK	316 d	4.99 c	1.59 c	0.340 d
Rate 1	421 c	8.39 ab	2.32 b	0.74 c
Rate 2	467 bc	9.61 a	2.63 b	0.94 b
Rate 3	549 ab	10.81 a	3.56 a	1.22 a
Rate 4	601 a	10.85 a	3.95 a	1.28 a
CF, chemical fertilizer; CK, no application of fertilizer. ^†Within columns, means followed by the same letter are not significantly different (P = 0.05) using Duncan's multiple range test.

Table 5 Effect of different application rates of compost on the enzymatic activities of the soils

Treatment	dHase	CMCase	Gase	Protease	Urease	aSase	aPase	Pase
	(µg TPF g^−1 h^−1)	(µg glu g^−1 h^−1)	(µg PNF g^−1 h^−1)	(µg tyr g^−1 h^−1)	(µg NH^+ 4 g^−1 h^−1)	(µg PNF g^−1 h^−1)
CF	87 d^‡	407 d	19.7 d	73.8 d	46.8 b	40.1 c	129 e	372 e
CK	61 e	430 cd	17.9 d	76.7 cd	50.1 b	43.0 c	133 e	407 de
Rate 1	102 bc	502 bc	26.7 c	122 bc	55.2 b	45.9 bc	173 d	434 cd
Rate 2	112 b	538 ab	27.8 c	131 bc	65.2 ab	53.8 ab	204 c	456 c
Rate 3	159 a	552 ab	36.1 b	123 b	67.7 ab	55.0 ab	238 b	463 b
Rate 4	151 a	594 a	43.9 a	187 a	84.4 a	59.4 a	272 a	588 a
^†Within columns, means followed by the same letter are not significantly different (P = 0.05) using Duncan's multiple range test. CF, chemical fertilizer; CK, no application of fertilizer; dHase, dehydrogenase; CMCase, cellulose; Gase, β-glucosidase; aSase, arylsulphatase; aPase, acid phosphatase; Pase, alkaline phosphatase.

Table 6 Effect of different application rates of compost on the growth of vegetables of the last four crops

Treatments	Pak-choi (21st crop)	Lettuce (22nd crop)	Amaranth (23rd crop)	Amaranth (24th)
	Fresh weight (Mg ha^−1)
CF	25.8 b^†	4.1 c	2.4 b	4.3 bc
CK	13.0 c	3.1 c	2.0 b	3.1 c
Rate 1	22.0 b	5.8 b	2.9 ab	4.9 b
Rate 2	27.6 a	6.9 b	3.1 a	7.3 a
Rate 3	29.0 a	10.1 a	3.7 a	8.3 a
Rate 4	27.5 a	11.3 a	3.1 a	8.0 a
^†Within columns, means followed by the same letter are not significantly different (P = 0.05) using Duncan's multiple range test. CF, chemical fertilizer; CK, no application of fertilizer.