Conversion factor (k factor) for estimation of soil microbial biomass potassium by the chloroform-fumigation extraction method 

Figures & data

Table 1. Soils used in this study.

Soil	Crop	Soil type	Soil texture	Total C (g kg^−1)	Total N (g kg^−1)	pH (H2O)	Ex-K^a (mg K kg^−1)
Paddy field soil (Anjo)^b	Rice(Oryza sativa L.)	Oxyaquic Dystrudept	LiC	14	1.2	6.2	165 (49^c)
Upland field soil (Togo; CF plot)	Maize (Zea mays L.)	Typic Dystrudept	LiC	9.5	1.2	5.3	177
Upland field soil (Togo; CM plot)	Maize (Zea mays L.)	Typic Dystrudept	LiC	29	3.0	5.6	415
Upland field soil (Ano; greenhouse)	Ginger (Zingiber officinale Roscoe)	Typic Melanudand	SiCL	72	3.6	6.1	ND^d

^a Exchangeable potassium; ^b data from Yamashita et al. (2014); ^c data under a flooded condition in this study; ^d not determined.

CF, chemical fertilizer; CM, chemical fertilizer with farmyard manure.

Table 2. Extracted K after chloroform-fumigation for paddy and upland soils inoculated with bacterial or fungal suspension with known K concentration.

	K concentration (mg K kg^−1 soil)
Soil with treatment	Microbial suspension	Inoculated (a)	Uninoculated (b)	(a)–(b)
1. Paddy field soil (Anjo; flooded)
1 + bacteria	59.8^CD	74.5	46.7	27.8^BC
1 + fungi	84.3^E	74.8	46.3	28.6^C
2. Paddy field soil (Anjo; drained)^a
2 + bacteria	43.8^ABC	189	173	16.1^A
2 + fungi	88.2^E	193	173	20.2^ABC
3. Upland field soil (Togo; CF plot)
3 + bacteria	71.0^D	180	158	22.5^ABC
3 + fungi	40.4^ABC	187	167	19.3^AB
4. Upland field soil (Togo; CM plot)
4 + bacteria	53.0^BCD	416	391	24.7^ABC
4 + fungi	31.6^AB	410	388	16.6^A
5. Upland field soil (Ano; greenhouse)
5 + bacteria	34.8^AB	594	569	22.1^ABC
5 + fungi	25.0^A	574	553	20.3^ABC

^a Data from Yamashita et al. (2014).

CF, chemical fertilizer; CM, chemical fertilizer with farmyard manure.

Different letters (A, B, C, D, E) indicate a significant difference (P < 0.05, Tukey test).

Table 3. Bacterial/fungal ratios (B:F), fractional conversion factors for bacteria (k_Kb) and fungi (k_Kf) and final conversion factor for microbial biomass potassium (k_K) after chloroform-fumigation extraction in paddy and upland field soils.

Soil	B:F^a	kKb	kKf	kK
Paddy field soil (Anjo; flooded)	35:65	0.46	0.34	0.38^AB
Paddy field soil (Anjo; drained)	35:65	0.37^b	0.23^b	0.28^A
Upland field soil (Togo; CF plot)	40:60	0.32	0.48	0.41^AB
Upland field soil (Togo; CM plot)	38:62	0.47	0.52	0.50^B
Upland field soil (Ano; greenhouse)	44:56	0.64	0.81	0.73^C

^a Ratio of bacterial biomass to fungal biomass determined by the substrate-induced respiration method; ^b data from Yamashita et al. (2014).

CF, chemical fertilizer; CM, chemical fertilizer with farmyard manure.

Different letters (A, B, C) indicate a significant difference (P < 0.05, Tukey test).

Yamashita K, Honjo H, Nishida M, Kimura M, Asakawa S 2014: Estimation of microbial biomass potassium in paddy field soil. Soil Sci. Plant Nutr. 59, 337–346. doi:10.1080/00380768.2014.919237 (Corrigendum [2016] 62, 570–573. doi:10.1080/00380768.2016.1234137).

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