Estimation of turnover time of microbial biomass potassium in paddy field soil

Figures & data

Table 1. Soil type and physicochemical properties of the soils

				Exchangeable K	Total C	Total N
Soil	Soil type^†	Texture	pH (H2O)	(mg kg^−1 soil)	(g kg^−1 soil)	(g kg^−1 soil)
Anjo	Oxyaquic Dystrudept	LiC	6.3	191	16.9	1.5
Omagari-1	Typic Fluvaquent	CL	5.1	107	21.9	1.9
Omagari-2	Typic Fluvaquent	CL	5.0	99.6	23.0	2.0

^†Soil Survey Staff (2014)

LiC, light clay; CL, clay loam

Figure 1. Changes in exchangeable K (cross symbols, control; circle symbols, CNP treatment). Closed symbols in CNP treatment indicate significant differences between control and CNP treatments (P < 0.05). Bars indicate S.E. (n = 3).

Figure 2. Changes in microbial biomass K (cross symbols, control; circle symbols, CNP treatment). Decay rate constants k in Anjo, Omagari-1, and −2 soils are 9.80 × 10⁻³, 1.12 × 10⁻², and 1.27 × 10⁻², respectively. Closed symbols in CNP treatment indicate significant differences between control and CNP treatments (P < 0.05). Lines express a first order exponential function. Bars indicate S.E. (n = 3).

Figure 3. Changes in microbial biomass C (cross symbols, control; circle symbols, CNP treatment). Decay rate constants k in Anjo, Omagari-1, and −2 soils are 5.96 × 10⁻³, 1.11 × 10⁻², and 9.94 × 10⁻³, respectively. Closed symbols in CNP treatment indicate significant differences between control and CNP treatments (P < 0.05). Lines express a first order exponential function. Bars indicate S.E. (n = 3).

Figure 4. Changes in microbial biomass N (cross symbols, control; circle symbols, CNP treatment). Decay rate constants k in Anjo, Omagari-1, and −2 soils are 5.78 × 10⁻³, 2.38 × 10⁻², and 1.92 × 10⁻², respectively. Closed symbols in CNP treatment indicate significant differences between control and CNP treatments (P < 0.05). Lines express a first order exponential function. Bars indicate S.E. (n = 3).

Table 2. Turnover time of microbial biomass K, C, and N. *

	K	C	N
Soil	Turnover time (d)
Anjo	98.5 ± 15.8^Aa	173 ± 17^Aa	175 ± 17^Aa
Omagari-1	92.4 ± 8.8^Aa	92.1 ± 8.7 ^Ba	40.3 ± 0.8^Bb
Omagari-2	80.4 ± 10.9^Aa	105 ± 13 ^Ba	51.5 ± 5.8^Bb

*The turnover time is indicated as averages ± S.E. from the measurements repeated three times.

Capital letters (A and B) and small letters (a and b) indicate significant differences among soils and elements, respectively (P < 0.05).

Soil Survey Staff. 2014. Keys to Soil Taxonomy. 12th ed. Washington, DC: United States Department of Agriculture.

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