Assessment of soil carbon and biochemical indicators of soil quality under rainfed land use systems in North Eastern region of Punjab, India

Figures & data

Figure 1. Location of the study area.

Table 1. Detail of land use systems and standard agronomic practices.

System	Sub-system	Standard agronomic practices
Forestry system	Chinaberry (Melia azedarach) based	Plantations were more than 15 years old. No intercrops as well as cultivation were taken in these fields. Leaf fall is the only source of organic manures.
	Eucalyptus based
	Populus (Populus deltoides) based
Agro-forestry system	Chinaberry (Melia azedarach) based	Plantations were less than 8 years old. The fodder crop during monsoon season and oil seed crops during winter season were grown as intercrop. The nitrogen 180 kg ha^−1 and phosphorus 60 kg ha^−1 were applied to these fields annually through chemical fertilizers
Horticulture system	Guava (Psidium guajava) based	Plantations were more than 15 years old. No intercrops as well as cultivation were taken in these fields. FYM @7-10 t ha^−1 were applied to the tree basin. In nurseries FYM @20 t ha^−1 were applied along with the cultivation practices.
	Mandarin hybrid (Citrus reticulata) based
	Mango (Mangiferaindica) based
	Nursery based
	Peach (Prunus persica) based
Agri-horticulture system	Gooseberry (Phyllanthus emblica) based	Plantations were less than 6 years old. The fodder crop during monsoon season and oil seed crops during winter season were grown as intercrop. The 200 kg ha^−1 nitrogen and 80 kg ha^−1 phosphorus along with FYM @8-10 t ha^−1 were applied to these fields annually through chemical fertilizers
	Guava (Psidium guajava) based
	Mandarin hybrid (Citrus reticulata) based
	Mango (Mangifera indica) based
	Peach based
Agriculture system	Maize – Wheat Fodder-oil seed	The agriculture systems comprised of maize-wheat and fodder-oil seed crop systems continuously cultivated for more than 10 years. Agricultural systems included application of recommended chemical fertilizers without organic manures. The 220 kg ha^−1 nitrogen and 100 kg ha^−1 phosphorus along with FYM @4-6 t ha^−1 were applied to these fields annually through chemical fertilizers
Barren lands	Eroded lands	Severely eroded soils with little vegetation without cultivation were included under barren lands.

Table 2. Effect of different land use systems on physicochemical properties of soil.

Land use system	Sub system	pH	EC (dS m^−1)	Textural class	Sand (%)	Silt (%)	Clay (%)
Forestry	Chinaberry	7.6 ± 0.09	0.48 ± 0.18^ab	Loamy sand	83.6 ± 3.4^bc	5.6 ± 1.7^c	10.8 ± 1.9^d
	Eucalyptus	7.6 ± 0.20	0.49 ± 0.10^abc	Loamy sand	83.1 ± 2.3^bc	8.8 ± 1.0^abc	12.5 ± 1.8^c d
	Populus	7.7 ± 0.09	0.56 ± 0.2^ab	Loamy sand	84.0 ± 3.1^abc	5.4 ± 2.3	10.6 ± 1.4^d
Agroforestry	Chinaberry	7.6 ± 0.18	0.46 ± 0.18^bc	Loamy sand	80.3 ± 2.3^bc	9.0 ± 2.5^abc	10.6 ± 1.0^d
Horticulture	Guava	7.4 ± 0.46	0.42 ± 0.15^c	Sandy loam	77.0 ± 0.6	11.8 ± 0.5^a	11.2 ± 0.1^c d
	Mandarin hybrid	7.5 ± 0.33	0.46 ± 0.17^bc	Sandy loam	86.0 ± 0.1^ab	4.3 ± 0.1	19.7 ± 0.1^a
	Mango	7.3 ± 0.36	0.61 ± 0.18^a	Sandy loam	81.2 ± 1.9^bc	7.0 ± 0.1^abc	11.7 ± 1.5^c d
	Nursery	7.5 ± 0.27	0.46 ± 0.13^bc	Sandy loam	90.0 ± 0.1^a	9.2 ± 0.1^abc	10.8 ± 0.1^d
	Peach	7.6 ± 0.18	0.45 ± 0.16^bc	Sandy loam	77.0 ± 0.6	10.9 ± 1.5^ab	10.7 ± 1.3^d
Agri- horticulture	Gooseberry	7.5 ± 0.23	0.42 ± 0.17^c	Sandy loam	76.0 ± 0.1	10.5 ± 0.1^abc	13.5 ± 0.1^b c d
	Guava	7.9 ± 0.04	0.38 ± 0.16^c	Sandy loam	85.0 ± 0.1^ab	6.7 ± 0.1^b	14.3 ± 0.1^b c
	Mandarin hybrid	7.7 ± 0.02	0.49 ± 0.19^abc	Loamy sand	82.0 ± 2.0^bc	6.9 ± 1.7^abc	11.1 ± 0.7^c d
	Mango	7.4 ± 0.11	0.45 ± 0.20^bc	Loamy sand	90.0 ± 0.1^ab	10.3 ± 0.1^abc	9.7 ± 0.1
	Peach	7.8 ± 0.25	0.31 ± 0.19	Sandy loam	75.6 ± 0.2	8.1 ± 1.0^abc	16.3 ± 1.3^b
Agriculture	Maize – Wheat	7.9 ± 0.08	0.42 ± 0.16^c	Sandy loam	77.2 ± 0.4	8.6 ± 1.6^abc	13.3 ± 1.8^b c d
	Fodder- oil seed	7.4 ± 0.08	0.43 ± 0.17^bc	Loamy sand	82.0 ± 2.3^bc	7.3 ± 2.3^abc	10.7 ± 0.1^d
Barren land	Uncultivated	7.6 ± 0.22	0.48 ± 0.15^a b	Loamy sand	83.3 ± 5.7^bc	9.5 ± 2.1^abc	10.6 ± 1.9^d
	LSD (P = 0.05)	NS	0.13		6.3	4.9	3.1

Table 3. Effect of different land use systems on soil organic carbon and labile soil carbon fractions.

Land use System	Sub system	SOC (%)	Labile fractions of carbon
			KMnO4-C (mg kg^−1)	WEOC (%)	DOXC (%)	DOC (%)
Forestry	Chinaberry	0.45 ± 0.07^bcd	1955 ± 989	0.016 ± 0.009	0.71 ± 0.22	0.0033 ± 0.002
	Eucalyptus	0.45 ± 0.09 ^bcd	2116 ± 930	0.016 ± 0.007	0.77 ± 0.25	0.0040 ± 0.002
	Populus	0.44 ± 0.03 ^bcd	2260 ± 905	0.014 ± 0.008	0.72 ± 0.26	0.0043 ± 0.002
Agro forestry	Chinaberry	0.43 ± 0.07^cd	1992 ± 714	0.015 ± 0.007	0.65 ± 0.27	0.0037 ± 0.002
Horticulture	Guava	0.38 ± 0.02^d	1960 ± 805	0.016 ± 0.007	0.62 ± 0.24	0.0037 ± 0.002
	Mandarin hybrid	0.37 ± 0.05 ^d	1998 ± 739	0.014 ± 0.007	0.59 ± 0.26	0.0033 ± 0.002
	Mango	0.40 ± 0.02 ^d	1928 ± 566	0.015 ± 0.007	0.65 ± 0.23	0.0037 ± 0.002
	Nursery	0.54 ± 0.07 ^abc	1993 ± 933	0.014 ± 0.005	0.67 ± 0.20	0.0037 ± 0.002
	Peach	0.50 ± 0.06 ^abcd	1941 ± 697	0.016 ± 0.008	0.60 ± 0.26	0.0037 ± 0.002
Agri-horticulture	Gooseberry	0.54 ± 0.07 ^abc	1767 ± 657	0.018 ± 0.008	0.80 ± 0.15	0.0037 ± 0.002
	Guava	0.63 ± 0.11^a	1778 ± 885	0.017 ± 0.007	0.85 ± 0.13	0.0040 ± 0.002
	Mandarin hybrid	0.54 ± 0.04 ^abc	2323 ± 670	0.014 ± 0.006	0.58 ± 0.26	0.0043 ± 0.002
	Mango	0.59 ± 0.18 ^ab	2209 ± 435	0.017 ± 0.006	0.76 ± 0.15	0.0043 ± 0.002
	Peach	0.56 ± 0.03 ^abc	2636 ± 408	0.017 ± 0.006	0.80 ± 0.16	0.0043 ± 0.002
Agriculture	Maize – wheat	0.26 ± 0.01	1915 ± 1098	0.015 ± 0.008	0.54 ± 0.20	0.0033 ± 0.002
	Fodder-oilseeds	0.25 ± 0.01	1972 ± 1060	0.014 ± 0.006	0.61 ± 0.20	0.0037 ± 0.002
Barren land	Uncultivated	0.20 ± 0.03	1392 ± 963	0.013 ± 0.007	0.47 ± 0.19	0.0033 ± 0.002
	LSD (P = 0.05)	0.15	NS	NS	NS	NS

SOC: Soil organic carbon; KMnO₄-C: Potassium permanganate oxidizable carbon; WEOC: Water extractable organic carbon; DOXC: Dichromate oxidizable organic carbon; DOC: Dissolved organic carbon.

Table 4. Effect of different land use systems on organic matter fractions of soil.

Land use System	Sub system	Non-humic substances (%)	Humic substances (%)	Fulvic (%)	Humic acid carbon	Humification index
Forestry	Chinaberry	0.011 ± 0.003	0.032 ± 0.015	0.019 ± 0.008	329 ± 60	0.202 ± 0.03
	Eucalyptus	0.008 ± 0.003	0.021 ± 0.014	0.015 ± 0.006	168 ± 30	0.264 ± 0.12
	Populus	0.011 ± 0.003	0.027 ± 0.017	0.019 ± 0.008	198 ± 93	0.212 ± 0.04
Agro forestry	Chinaberry	0.009 ± 0.003	0.027 ± 0.019	0.017 ± 0.008	250 ± 90	0.220 ± 0.10
Horticulture	Guava	0.009 ± 0.004	0.026 ± 0.015	0.014 ± 0.006	234 ± 47	0.135 ± 0.03
	Mandarin hybrid	0.009 ± 0.004	0.026 ± 0.017	0.018 ± 0.006	228 ± 74	0.141 ± 0.03
	Mango	0.010 ± 0.003	0.027 ± 0.015	0.017 ± 0.005	227 ± 69	0.144 ± 0.03
	Nursery	0.009 ± 0.003	0.020 ± 0.017	0.019 ± 0.008	173 ± 78	0.179 ± 0.06
	Peach	0.008 ± 0.005	0.023 ± 0.014	0.021 ± 0.009	147 ± 66	0.170 ± 0.03
Agri-horticulture	Gooseberry	0.014 ± 0.004	0.032 ± 0.014	0.019 ± 0.009	316 ± 19	0.239 ± 0.09
	Guava	0.013 ± 0.006	0.027 ± 0.010	0.018 ± 0.008	166 ± 29	0.232 ± 0.08
	Mandarin hybrid	0.015 ± 0.004	0.025 ± 0.016	0.016 ± 0.009	242 ± 11	0.215 ± 0.10
	Mango	0.015 ± 0.007	0.045 ± 0.022	0.022 ± 0.009	193 ± 77	0.253 ± 0.11
	Peach	0.013 ± 0.001	0.024 ± 0.016	0.021 ± 0.009	222 ± 23	0.223 ± 0.12
Agriculture	Maize – wheat	0.009 ± 0.005	0.023 ± 0.012	0.019 ± 0.010	171 ± 70	0.127 ± 0.03
	Fodder-oilseeds	0.007 ± 0.002	0.025 ± 0.015	0.018 ± 0.010	151 ± 83	0.129 ± 0.03
Barren land	Uncultivated	0.006 ± 0.001	0.021 ± 0.010	0.014 ± 0.004	133 ± 63	0.095 ± 0.03
	LSD (P = 0.05)	NS	NS	NS	NS	NS

Table 5. Effect of different land use systems on oxidizable fractions of soil carbon.

Land use system	Sub system	Very labile C (%)	Labile C (%)	Less labile C (%)	Recalcitrant C (%)	TOC (%)	CMI (%)
Forestry	Chinaberry	0.13 ± 0.04	0.16 ± 0.05^b	0.12 ± 0.06^ab	0.68 ± 0.19^ab	1.74 ± 0.18	21.5 ± 4.18^cd
	Eucalyptus	0.12 ± 0.05	0.13 ± 0.07	0.12 ± 0.04^ab	0.34 ± 0.25	0.83 ± 0.32	18.9 ± 4.77
	Populus	0.14 ± 0.05	0.20 ± 0.04^ab	0.12 ± 0.04^ab	0.38 ± 0.11	1.83 ± 0.69	16.8 ± 5.70
Agro forestry	Chinaberry	0.13 ± 0.06	0.18 ± 0.06^ab	0.11 ± 0.02^b	0.46 ± 0.06^d	1.25 ± 0.04	19.8 ± 5.23^d
Horticulture	Guava	0.12 ± 0.05	0.13 ± 0.02	0.07 ± 0.02	0.47 ± 0.11^c	4.68 ± 0.66^a	16.2 ± 3.06
	Mandarin hybrid	0.14 ± 0.04	0.17 ± 0.06^ab	0.11 ± 0.03^b	0.46 ± 0.12^d	3.52 ± 0.80^bc	20.1 ± 4.04^d
	Mango	0.13 ± 0.06	0.18 ± 0.04^ab	0.10 ± 0.04^b	0.39 ± 0.11	1.36 ± 0.11	19.4 ± 5.03
	Nursery	0.11 ± 0.06	0.18 ± 0.04^ab	0.09 ± 0.01	0.50 ± 0.15^cd	2.89 ± 0.26^cd	17.9 ± 4.43
	Peach	0.13 ± 0.05	0.15 ± 0.05^a	0.13 ± 0.03^ab	0.42 ± 0.11	1.67 ± 0.60	18.4 ± 4.64
Agri- horticulture	Gooseberry	0.22 ± 0.01	0.15 ± 0.03^b	0.15 ± 0.06^a	0.44 ± 0.15^d	2.60 ± 0.07^d	27.2 ± 5.53^a
	Guava	0.17 ± 0.02	0.17 ± 0.02^ab	0.11 ± 0.03^b	0.59 ± 0.14^bc	2.30 ± 0.36^d	26.6 ± 2.06^ab
	Mandarin hybrid	0.15 ± 0.02	0.23 ± 0.05^a	0.12 ± 0.04^ab	0.72 ± 0.18^a	1.72 ± 0.28	24.7 ± 0.15^b
	Mango	0.18 ± 0.06	0.18 ± 0.08^ab	0.09 ± 0.05	0.56 ± 0.20^bcd	2.05 ± 0.31	22.5 ± 5.98^c
	Peach	0.18 ± 0.06	0.21 ± 0.03^ab	0.11 ± 0.05^b	0.43 ± 0.14	1.05 ± 0.08	25.0 ± 4.06^b
Agriculture	Maize – Wheat	0.10 ± 0.04	0.17 ± 0.02^ab	0.10 ± 0.03^b	0.38 ± 0.09	2.58 ± 0.79^d	17.2 ± 2.54
	Fodder- Oilseeds	0.10 ± 0.04	0.19 ± 0.03^a	0.06 ± 0.02	0.32 ± 0.11	1.81 ± 0.17	16.5 ± 2.99
Barren land	Uncultivated	0.09 ± 0.04	0.09 ± 0.03	0.02 ± 0.01	0.15 ± 0.11	1.15 ± 0.20	11.0 ± 3.58
	LSD (P = 0.05)	NS	0.06	0.03	0.12	0.67	2.0

TOC- total organic carbon (%), CMI- carbon management index (%).

Table 6. Effect of different land use systems on dehydrogenase activity, microbial and metabolic quotients.

Land use System	Sub system	Dehydrogenase Activity ((µgTPFg^−1h^−1)	Basal Soil Respiration (µg CO2 g^−1soil h^−1)	Microbial Biomass Carbon (µgg^−1 soil)	Metabolic quotient	Metabolic potential	Microbial quotient
Forestry	Chinaberry	9.9 ± 1.0^abc	0.27 ± 0.001	127.5 ± 15.0^e	0.0021 ± 0.0001^b	618.8 ± 12.0	73.3 ± 1.4
	Eucalyptus	9.5 ± 0.6^abc	0.22 ± 0.004	162.3 ± 14.3^bcd	0.0034 ± 0.0001^a	593.8 ± 10.0	195.5 ± 9.8
	Populus	10.1 ± 1.2^abc	0.19 ± 0.010	101.9 ± 6.1	0.0019 ± 0.0002^c	721.4 ± 9.7	55.7 ± 3.1
Agro Forestry	Chinaberry	9.8 ± 1.4^abc	0.22 ± 0.004	116.9 ± 18.3	0.0019 ± 0.0006^c	653.3 ± 11.0	93.5 ± 4.2
Horticulture	Guava	9.9 ± 1.3^abc	0.23 ± 0.001	97.4 ± 11.7	0.0024 ± 0.0005^abc	618.8 ± 10.7	20.8 ± 4.3
	Mandarin hybrid	9.3 ± 1.8^abc	0.18 ± 0.003	89.1 ± 7.8	0.0020 ± 0.0008^bc	664.3 ± 12.1	25.3 ± 3.9
	Mango	9.5 ± 2.0^abc	0.20 ± 0.005	231.7 ± 0.7^a	0.0029 ± 0.0001^abc	633.3 ± 11.4	170.4 ± 8.7
	Nursery	10.9 ± 1.7^a	0.18 ± 0.003	76.8 ± 10.2	0.0023 ± 0.0002^bc	778.6 ± 21.3	26.6 ± 5.9
	Peach	9.0 ± 1.6^bc	0.14 ± 0.003	90.5 ± 7.0	0.0015 ± 0.0003	562.5 ± 15.7	54.2 ± 7.1
Agri- horticulture	Gooseberry	10.5 ± 1.7^ab	0.16 ± 0.007	173.6 ± 16.9^c	0.0029 ± 0.0004^abc	583.3 ± 14.7	66.8 ± 5.9
	Guava	10.2 ± 0.4^abc	0.26 ± 0.005	154.9 ± 24.4^c	0.0017 ± 0.0001	600.0 ± 13.3	67.3 ± 6.5
	Mandarin hybrid	10.0 ± 1.6^abc	0.24 ± 0.003	121.6 ± 4.2^e	0.0020 ± 0.0005^bc	714.3 ± 11.2	70.7 ± 7.6
	Mango	9.9 ± 2.1^abc	0.23 ± 0.010	184.5 ± 4.1^b	0.0012 ± 0.0004	582.4 ± 18.6	90.0 ± 8.7
	Peach	9.5 ± 1.8^abc	0.24 ± 0.002	143.7 ± 7.1^de	0.0017 ± 0.0007	558.8 ± 12.4	136.9 ± 7.6
Agriculture	Maize – wheat	8.9 ± 1.1^bc	0.18 ± 0.003	116.2 ± 4.6	0.0015 ± 0.0006	593.3 ± 14.5	45.0 ± 3.9
	Fodder- oil seed	8.4 ± 1.3^c	0.24 ± 0.004	68.2 ± 27.9	0.0030 ± 0.0001^ab	607.1 ± 13.3	37.7 ± 2.4
Barren land	Uncultivated	5.4 ± 1.6	0.13 ± 0.001	34.9 ± 10.1	0.0011 ± 0.0004	415.4 ± 15.7	30.3 ± 1.9
	LSD (P = 0.05)	1.8	NS	24.5	0.001	70.9	5.9

Figure 2. Principal component analysis for soil properties and systems.

DHA: Dehydrogenase Activity; BSR: Basal Soil Respiration; MBC: Microbial Biomass Carbon; KMnO₄-C: Potassium Permanganate Extractable Carbon; WEOC: Water Extractable Organic Carbon; DOXC: Dichromate Oxidizable Carbon; DOC: Dissolved Organic Carbon; NH: Non Humic Substances; HS: Humic Substances; FA: Fulvic Acid; HAC: Humic Acid Carbon; HI: Humification Index; VL: Very Labile Carbon; LC: Labile Carbon; LLC: Less Labile Carbon; RC: Recalcitrant Carbon; TOC: Total Organic Carbon; CMI: Carbon Management Index; MP: Metabolic potential; MQ: Metabolic Quotient; Qmic: Microbial quotient.

FD- Forestry chinaberry based, FE-Forestry eucalyptus based, FP-Forestry populus based, FE-Agroforestry chinaberry based, HG-Horticulture guava based, HK-Horticulture mandarin hybrid based, HM-Horticulture mango based, HN-Horticulture nursery based, HP-Horticulture peach based, AA-Agri-horticulture gooseberry based, AG-Agri-horticulture guava based, AM-Agri-horticulture mango based, AP-Agri-horticulture peach based, MW- Agriculture maize-wheat based, FO-Agriculture fodder-oilseed based

Figure 3. Average effect of different land use systems on soil quality index and the individual contribution of each of the key indicators. CMI-carbon management index, MP-metabolic potential, TOC- total organic carbon, LLC – less labile carbon and FA- fulvic acid.

Figure 4. Contribution (%) of selected indicators to soil quality under different land use system (CMI-carbon management index, MP-metabolic potential, TOC- total organic carbon, LLC – less labile carbon and FA- fulvic acid).

Figure 5. Overall contribution of the selected soil quality indicators to soil quality index. (CMI-carbon management index, MP-metabolic potential, TOC- total organic carbon, LLC – less labile carbon and FA- fulvic acid).

Table 7. Supplementary data indication the loading values and contribution of variable in principal component analysis.

	Loading values of PC1	Contribution of PC1	Loading values of PC2	Contribution of PC2	Loading values of PC3	Contribution of PC3	Loading values of PC4	Contribution of PC5	Loading values of PC5	Contribution of PC5
WEOC	0.733	5.867	−0.360	4.946	0.419	9.140	−0.062	0.267	−0.044	0.151
DOXC	0.818	7.304	−0.232	2.042	−0.025	0.032	−0.074	0.383	−0.048	0.179
DOC	0.603	3.969	−0.086	0.279	−0.533	14.769	−0.294	6.089	0.182	2.555
NHS	0.869	8.226	0.109	0.452	0.057	0.168	−0.289	5.893	0.069	0.362
HS	0.577	3.635	−0.040	0.061	0.363	6.844	−0.458	14.761	0.022	0.036
FA	0.511	2.844	0.016	0.010	0.082	0.353	−0.141	1.407	0.688	36.410
HAC	0.548	3.274	0.235	2.112	0.378	7.443	0.149	1.572	−0.404	12.560
HI	0.844	7.759	−0.198	1.495	−0.194	1.951	−0.028	0.054	−0.019	0.028
VL	0.844	7.771	−0.139	0.733	0.294	4.490	−0.148	1.549	0.172	2.284
LC	0.538	3.160	0.450	7.724	−0.531	14.690	−0.101	0.726	0.239	4.394
LLC	0.769	6.444	0.042	0.068	0.062	0.197	0.505	17.949	0.149	1.707
RC	0.685	5.121	0.534	10.863	0.018	0.016	−0.123	1.072	−0.211	3.408
TOC	−0.063	0.043	0.636	15.410	0.574	17.176	0.051	0.185	−0.057	0.249
CMI	0.902	8.875	0.020	0.016	0.097	0.492	−0.071	0.360	−0.016	0.019
DHA	0.794	6.881	0.440	7.380	−0.042	0.090	0.276	5.373	−0.023	0.039
BSR	0.502	2.746	0.213	1.734	−0.307	4.911	−0.396	11.047	−0.568	24.802
MBC	0.758	6.258	−0.378	5.434	0.009	0.004	0.186	2.451	−0.197	2.975
MQ	−0.767	6.419	0.230	2.015	−0.141	1.034	−0.466	15.281	−0.141	1.531
MP	0.340	1.259	0.748	21.315	−0.365	6.939	0.349	8.596	0.036	0.098
Qmic	0.443	2.145	−0.646	15.912	−0.422	9.261	0.266	4.984	−0.284	6.212

SOC: Soil organic carbon (%); KMnO₄-C: Potassium permanganate oxidizable carbon (mg kg⁻¹); WEOC: Water extractable organic carbon (%); DOXC: Dichromate oxidizable organic carbon (%); DOC: Dissolved organic carbon (%), NHS - Non-humic substances (%), HS - Humic substances (%), FA - Fulvic (%), HAC - Humic acid carbon, HI - Humification index, VL - Very labile C (%), LC - Labile C (%), LLC-Less labile C (%), RC-Recalcitrant C (%), TOC- total organic carbon (%), CMI- cabon management index (%),DHA- Dehydrogenase Activity ((µgTPFg⁻¹h⁻¹), BSR- Basal Soil Respiration (µg CO₂ g⁻¹soil h⁻¹), MBC- Microbial Biomass Carbon (µgg⁻¹ soil), MQ-Metabolic quotient, MP-Metabolic potential , Qmic- Microbial Quotient.