The mass water content of paddy soil after harvest is strongly associated with the accumulation of organic matter as the source of available nitrogen

Figures & data

Figure 1. Locations of 31 soil sampling sites.

† Prefectures were covered by above symbols according to the soil type at the sampling sites

Table 1. Test site (location), soil classification, soil texture, sampling year, total nitrogen of soil (TN), total carbon of soil (TC), available nitrogen of soil (AN), and Nearby AMeDAS in Toyama prefecture

Site location		Soil group^†	Soil texture (ISSS method)	Sampling year	Years	Soil sampled in 2018^‡			Nearby AMeDAS^§
						TN	TC	AN
						g kg^−1	g kg^−1	mg kg^−1
Toyama	Yoshioka	Gray Lowland soil	SL	2015–2019	5	1.82	19.7	115	Ooyama
Toyama	Nunoichi	Gray Lowland soil	L	2015–2019	5	2.39	26.4	152	Akigashima
Kurobe	Urayama	Gray Lowland soil	SL	2015–2019	5	1.92	22.8	192	Unazuki
Himi	Kamikuzuro	Gley soil	L	2015–2018	4	2.13	22.8	214	Himi
Toyama	Hamakurosaki	Gley soil	CL	2015–2019	5	3.05	34.5	197	Toyama
Kamiichi	Hironoshin	Andosol	CL	2015–2018	4	4.00	56.3	241	Kamiichi
Nanto	Takeuchi	Andosol	CL	2015–2019	5	4.18	50.8	367	Nanto-Takamiya
Himi	Kume	Gley Upland soil	LiC	2016–2018	3	2.98	31.6	374	Himi
Toyama	Yatsuomachi-Shinden	Gley Upland soil	LiC	2016–2018	4	2.08	23.8	196	Yatsuo

† Soils were classified into 18 soil groups using Classification of cultivated soils in Japan second approximation Revised edition (1983). The Gley soil and a Gray Lowland soil are divided by groundwater level, the Gley soils have a saturated layer with reducing conditions within subsoil whereas the groundwater level is deeper in Gray Lowland Soils.

‡ TN, TC, and AN in 2018 stated as the latest data.

§ For predicting precipitation in the site, the nearest AMeDAS date was used.

Table 2. Mass water content after harvest of soil (MWH), sampling day, and situation of precipitation at each sites in 3–5 years in Toyama prefecture

Site Soil group	Soil texture	Sampling year	Mass water content after harvest (MWH)		The rate against average in MWH	Sampling day	Continuous days of no-precipitation days^†	Precipitation of the last rainy day (mm day^-1)^‡	Accumulation of precipitation before soil sampling (mm)§
				Ave.±S.D. of MWH (kg kg^−1)
			kg kg^−1	(coefficient of variation)					24 hours	7 days
Yoshioka	SL	2015	0.494		0.99	Oct. 1st	5	35.0	0	50.0
Toyama-city		2016	0.511	0.498	1.03	Sep. 27th	0	1.0	0	116.0
		2017	0.457	±0.025	0.92	Sep. 26th	3	1.5	0	13.5
Gray Lowland soil		2018	0.521	(0.050)	1.05	Sep. 28th	0	5.0	0	57.5
		2019	0.508		1.02	Sep. 26th	1	16.0	0	19.5
Nunoichi	L	2015	0.590		0.93	Sep. 29th	3	29.5	0	44.0
Toyama-city		2016	0.605	0.637	0.95	Sep. 16th	0	1.5	0	44.5
		2017	0.642	±0.039	1.01	Sep. 21th	0	5.5	0	51.0
Gray Lowland soil		2018	0.676	(0.061)	1.06	Sep. 21th	0	11.0	11.0	95.5
		2019	0.672		1.05	Sep. 24th	1	1.0	1.5	20.0
Urayama	SL	2015	0.547		0.89	Sep. 24th	5	20.5	0.5	25.0
Kurobe-city		2016	0.649	0.613	1.06	Sep. 26th	2	15.5	0	115.0
		2017	0.594	±0.054	0.97	Sep. 20th	1	72.0	0	82.5
Gray Lowland soil		2018	0.591	(0.089)	0.96	Sep. 20th	1	10.5	0	87.0
		2019	0.686		1.12	Sep. 24th	0	5.0	6.5	28.0
Kamikuzuro	L	2015	0.692	0.649	1.07	Oct. 1st	5	33.5	0	47.5
Himi-city		2016	0.625	±0.031	0.96	Sep. 5th	5	40.5	0	40.5
		2017	0.627	(0.048)	0.97	Sep. 25th	4	10.5	0	39.5
Gley soil		2018	0.652		1.00	Sep. 25th	4	10.5	4.0	19.5
Hamakurosaki	CL	2015	0.773		0.97	Sep. 29th	3	33.0	0	46.0
Toyama-city		2016	0.800	0.800	1.00	Sep. 16th	2	45.0	0	47.0
		2017	0.795	±0.028	0.99	Sep. 20th	1	32.0	0	36.5
Gley soil		2018	0.847	(0.035)	1.06	Sep. 20th	2	10.5	0	98.5
		2019	0.784		0.98	Sep. 24th	4	12.0	0.5	29.0
Hironoshin	CL	2015	0.869	0.885	0.98	Sep. 29th	3	37.0	0	51.0
Kamiichi-town		2016	0.866	±0.023	0.98	Sep. 16th	1	3.0	0	51.0
		2017	0.890	(0.026)	1.01	Sep. 21th	0	6.5	0	52.5
Andosol		2018	0.916		1.03	Sep. 20th	2	13.5	0	79.5
Takeuchi	CL	2015	1.012		0.97	Sep. 30th	2	5.0	0	45.0
Nanto-city		2016	1.068	1.044	1.02	Sep. 26th	2	5.5	0	163.5
		2017	0.907	±0.089	0.87	Sep. 25th	4	11.0	0	59.5
Andosol		2018	1.101	(0.085)	1.05	Sep. 21th	0	6.5	6.5	55.5
		2019	1.132		1.08	Sep. 25th	0	14.0	7.5	17.0
Kume	LiC	2016	0.876	0.925	0.95	Sep. 5th	5	40.5	0	40.5
Himi-city		2017	0.953	±0.043	1.03	Sep. 25th	4	10.5	0	39.5
Gley Upland soil		2018	0.946	(0.046)	1.02	Sep. 25th	4	10.5	4.0	19.5
Yatsuomachi-sinden	LiC	2016	0.682	0.711	0.96	Sep. 26th	2	4.0	0	182.0
Toyama-city		2017	0.689	±0.030	0.97	Sep. 20th	1	31.0	0	43.0
		2018	0.742	(0.042)	1.04	Sep. 25th	2	9.5	11.0	21.0
Gley Upland soil		2019	0.732		1.03	Sep. 26th	1	25.0	0	32.0

†Continuous days from the last day of precipitation of 1 mm day^-1 or more before soil sampling

‡Precipitation at the last rainy day of 1 mm day^-1 or more before soil sampling

§‘24 hours’ means precipitation within 24 h from the time of soil sampling

‘7 days’ does not include precipitation on the day of soil sampling

Table 3. Mass water content after harvest of soil (MWH), sampling day, and situation of precipitation at each sites in 3 years throughout Japan

Test site	Plot treatment^†	Sampling year	Mass water content after harvest (MWH)	Ave.±S.D.	The rate against average in MWH	Sampling day	continuous days of no-precipitation days^†	Precipitation of the last rainy day (mm day^-1)^§	Accumulation of precipitation before soil sampling (mm)¶
Soil group				of MWH (kg kg^−1)
Soil texture			kg kg^−1						24 hours	7 days
Yamagata	CF	2011	0.427	0.404	1.06	Oct. 13th	1	1.5	0	21
	a	2012	0.405	±0.024	1.00	Oct. 17th	3	3	0	3
Gray		2013	0.379	(0.060)	0.94	Oct. 9th	4	1	0	2
Lowland	NN	2011	0.407	0.408	1.00	Oct. 13th	1	1.5	0	21
soil	a	2012	0.438	±0.030	1.07	Oct. 17th	3	3	0	3
		2013	0.378	(0.074)	0.93	Oct. 9th	4	1	0	2
LiC	CF + RSC	2011	0.538	0.534	1.01	Oct. 13th	1	1.5	0	21
	b	2012	0.571	±0.039	1.07	Oct. 17th	3	3	0	3
		2013	0.493	(0.073)	0.92	Oct. 9th	4	1	0	2
Ryugasaki	CF	2011	0.309	0.321	0.96	Oct. 5th	12	2	0	0
	a	2012	0.327	±0.010	1.02	Oct. 15th	0	3.5	3.5	14
Gray		2013	0.326	(0.032)	1.02	Oct. 23th	2	53.5	0	249
Lowland	CF + RS	2011	0.363	0.389	0.93	Oct. 5th	12	2	0	0
soil	b	2012	0.393	±0.025	1.01	Oct. 15th	0	3.5	3.5	14
		2013	0.412	(0.063)	1.06	Oct. 23th	2	53.5	0	249
SCL	CF + CMC	2011	0.371	0.415	0.89	Oct. 5th	12	2	0	0
	b	2012	0.434	±0.038	1.05	Oct. 15th	0	3.5	3.5	14
		2013	0.439	(0.091)	1.06	Oct. 23th	2	53.5	0	249
Gifu	CF	2011	0.327	0.327	1.00	Oct. 21th	4	14.5	0	82
	a	2012	0.297	±0.031	0.91	Oct. 15th	8	1	0	0
Gray		2013	0.358	(0.093)	1.09	Oct. 29th	2	6.5	0.5	57
Lowland	CF + RS	2011	0.335	0.345	0.97	Oct. 21th	4	14.5	0	82
soil	ab	2012	0.298	±0.053	0.86	Oct. 15th	8	1	0	0
		2013	0.403	(0.154)	1.17	Oct. 29th	2	6.5	0.5	57
CL	CF + CMC	2011	0.396	0.383	1.03	Oct. 21th	4	14.5	0	82
	b	2012	0.330	±0.047	0.86	Oct. 15th	8	1	0	0
		2013	0.422	(0.124)	1.10	Oct. 29th	2	6.5	0.5	57
Oogata	CF	2011	0.623	0.562	1.11	Oct. 13th	0	10	10	47
	a	2012	0.525	±0.053	0.93	Oct. 11th	5	9	17.5	9
Gley		2013	0.537	(0.095)	0.96	Nov. 8th	0	39.5	11.5	50
soil	NN	2011	0.568	0.529	1.07	Oct. 13th	0	10	10	47
	a	2012	0.504	±0.034	0.95	Oct. 11th	5	9	17.5	9
LiC		2013	0.516	(0.064)	0.97	Nov. 8th	0	39.5	11.5	50
	CF + CMC	2011	0.766	0.699	1.10	Oct. 13th	0	10	10	47
	b	2012	0.643	±0.062	0.92	Oct. 11th	5	9	17.5	9
		2013	0.687	(0.089)	0.98	Nov. 8th	0	39.5	11.5	50
Jouetsu	CF	2011	0.661	0.684	0.97	Oct. 13th	1	4.5	0	26
	a	2012	0.655	±0.045	0.96	Oct. 26th	2	21.5	0	22
Gley		2013	0.736	(0.066)	1.08	Nov. 1st	1	4	0	95
soil	CF + RS	2011	0.770	0.814	0.95	Oct. 13th	1	4.5	0	26
	b	2012	0.790	±0.059	0.97	Oct. 26th	2	21.5	0	22
LiC		2013	0.881	(0.073)	1.08	Nov. 1st	1	4	0	95
	CF + Compost	2011	0.734	0.787	0.93	Oct. 13th	1	4.5	0	26
	b	2012	0.811	±0.046	1.03	Oct. 26th	2	21.5	0	22
		2013	0.815	(0.058)	1.04	Nov. 1st	1	4	0	95

†There are not significant differences at the 5% level in the plots of same letters in each sites.

‡Continuous days from the last day with precipitation of 1 mm day^-1 or more before soil sampling

§Precipitation at the last rainy day of 1 mm day^-1 or more before soil sampling

‘24 hours’ means precipitation within 24 h from the time of soil sampling

‘7 days’ does not include precipitation on the day of soil sampling

Figure 2. Relationships between available nitrogen of soil (AN) and physicochemical properties of soil in control plots. a) Cation exchange capacity vs AN, b) Soil water-holding capacity vs AN (Total n = 30; Gley soil, n = 9; Andosol, n = 4; Shirasu, n = 1; Others (Gray Lowland soil and Yellow Soil), n = 16).

†Regression equation of non-Andosols (N) was obtained from Gley soils and Others, which of Andosols (A) was obtained from Andosols. Regression equation (T) was obtained from all samples.

Figure 3. Relationships between available nitrogen of soil (AN) and physicochemical properties of soil in control plots. a) Total nitrogen vs AN, b) Mass water content after harvest vs AN (Total n = 30; Gley soil, n = 9; Andosol, n = 4; Shirasu, n = 1; Others (Gray Lowland soil and Yellow Soil), n = 16).

†Regression equation of non-Andosols (N) was obtained from Gley soils and Others, which of Andosols (A) was obtained from Andosols. Regression equation (T) was obtained from all samples.

Figure 4. Influence of organic matter application (OMA), and paddy-upland rotation on the relationships between available nitrogen of soil (AN) and physicochemical properties of soil, a) total nitrogen vs AN, b) mass water content after harvest vs AN.

† Regression equation of non-volcanic soils (N) were obtained from 〇, ●, and □ (n = 79), which of volcanic soils (V) were obtained from Δ, ▲, and × (n = 21). Regression equation (T) was obtained from all samples.‡ Chiba soils were contaminated by the surrounding Andosols, and indicated by the same symbol as volcanic soils.§ In Yamagata, supplementary soil was added to topsoil in 1994. Parent material of supplementary soil was not paddy fields that had few-organic matter. As a result, the CF + RSC plot was indicated by the same symbol as non OMA in test period (Excluding volcanic soils).

Figure 5. Relationship between the accumulation of continuous no-precipitation days before sampling and rate against average in mass water content after harvest (MWH) in each site.

†Relative MWH value to average of MWH in each site were expressed the ratio of MWH at each year to the average value of MWH in the whole experimental duration

Figure 6. Relationship between total nitrogen of soil and soil water holding capacity. (Total n = 100).

† Regression equation of non-volcanic soils (N) was obtained from 〇, ●, and □ (n = 79), which of volcanic soils (V) were obtained from Δ and ▲ (n = 21). Regression equation (T) was obtained from all samples.

Figure 7. Relationship between soil water holding capacity and mass water content after harvest (Total n = 100).

† Regression equation of non-volcanic soils (N) were obtained from 〇, ●, and □ (n = 79), which of volcanic soils (V) were obtained from Δ and ▲ (n = 21). Regression equation (T) was obtained from all samples.

Figure 8. Relationship between the difference of available nitrogen of soil and the difference of mass water content after harvest (the difference obtained by subtracting the control plots from organic matter application, no-fertilizer, no-nitrogen, and paddy–upland rotation test plots). (n = 67).

The national institute of agro-environmental science. 1983. “Classification of Cultivated Soils in Japan Second Approximation Revised Edition.”

 Google Scholar