Effect of organic and inorganic fertilizers and rice straw on carbon sequestration and soil fertility under a rice–rice cropping pattern

Figures & data

Table 1. Carbon and nutrient status of the organic materials applied in the experimental field.

Organic materials	Moisture (%)	OC	N	P	K	S	Zn (mg kg^−1)	C:N ratio
		(g kg^−1)
CD	69.6 ± 0.16	200 ± 9.2	9.92 ± 0.4	9.04 ± 1.2	9.33 ± 0.6	4.42 ± 0.8	124 ± 18	20.20
PM	33.6 ± 4.77	120 ± 11.3	17.12 ± 1.0	23.43 ± 1.3	12.71 ±1.5	8.01 ± 1.2	205 ± 19	7.02
RS	26.2 ± 0.03	400 ± 15.7	4.93 ± 0.2	1.04 ± 0.2	16.02 ± 1.0	0.84 ±0.2	36 ± 10	81.63

CD: Cow dung; OC: Organic carbon; PM: Poultry manure; RS: Rice straw.

Figure 1. Effect of organic manures, rice straw and inorganic fertilizer management practices on CO₂ emission (kg CO₂ ha⁻¹ wk⁻¹) during T. aman rice in different years: (a) 2010, (b) 2011 and (c) 2012. CD = cow dung, PM = poultry manure, RS = rice straw, STB = soil test-based fertilizer.

Figure 2. Effect of organic manures, rice straw and inorganic fertilizer management practices on CO₂ emission (kg CO₂ ha⁻¹ wk⁻¹) during boro rice in different years: (a) 2011 and (b) 2012. Cont. = control, CD = cow dung, PM = poultry manure, RS = rice straw, STB = soil test-based fertilizer.

Table 2. Effect of organic manures, rice straw and inorganic fertilizer on cumulative CO₂ emission, C loss and accumulation.

	Cumulative CO2 emission in crop seasons (kg/ha/14 weeks of each T. aman & boro) and fallow period of 336 days
Treat.	Aman 10	Aman 11	Aman 12	Boro 11	Boro 12	Fallow	Total CO2	Total C emission	Total C input (kg)	C emission loss (%)	C seq. (%)	C unaccounted (%)
Control	3832	4038	3827	3688	3729	5760	24874	6784	–	–	–	–
CD	5527	6159	5650	5679	5919	9000	37935	10346	10000	36	30	34
PM	5415	6042	5527	5563	5811	6840	35198	9599	10000	28	49	23
RS	5620	6282	5709	5762	6012	9000	38385	10469	10000	37	10	53
STB	4567	4905	4635	4591	4675	6120	29493	8044	–	–	–	–
CV (%)	9.0	8.3	5.8	6.7	8.5	10.3
LSD (0.05)	275	421	410	341	437	492

CD: Cow dung; PM: Poultry manure; RS: Rice straw; STB: Soil test-based fertilizer; Treat.: Treatment; CV: Coefficient of variation; LSD: Least significant difference.

Table 3. Effect of organic manures, rice straw and inorganic fertilizers on bulk density, carbon stock and carbon accumulation in soil after harvesting of five rice crops (0–15 cm soil depth).

	Initial soil				Post-harvest soil
Treatment	OC (g kg^−^1)	BD (g cm^−^3)	C Stock (t ha^−^1)	Labile C (g kg^−^1)	OC (g kg^−^1)	BD (g cm^−^3)	C Stock (t ha^−^1)	Carbon accumulation (t ha^−^1)
Control	11.30	1.38	23.39	2.92	10.82	1.36	22.03	− 1.36
CD	11.30	1.38	23.39	5.70	13.93	1.27	26.42	3.03
PM	11.30	1.38	23.39	4.88	14.54	1.30	28.30	4.90
RS	11.30	1.38	23.39	6.98	13.22	1.24	24.43	1.04
STB	11.30	1.38	23.39	3.78	11.83	1.32	23.43	0.04
CV (%)	–	–	–	–	3.3	1.9	4.8	80.1
LSD (0.05)	–	–	–	–	0.81	0.046	2.78	2.31

BD: Bulk density; CD: Cow dung; OC: Organic carbon; PM: Poultry manure; RS: Rice straw; STB: Soil test-based fertilizer; CV: Coefficient of variation; LSD: Least significant difference.

Table 4. Effect of different organic manures, rice straw and inorganic fertilizers on grain yields of T. aman and boro rice.

		Yield of rice grain at harvesting (t ha^−1)
Treatments	T. aman 2010	Boro 2011	T. aman 2011	Boro 2012	T. aman 2012
Control	3.81	3.97	3.64	3.86	3.46
Cow dung	5.29	6.59	5.40	6.72	5.45
Poultry manure	5.43	6.70	5.53	6.83	5.61
Rice straw	4.68	5.93	5.01	6.09	5.12
STB	5.00	6.48	5.23	6.54	5.26
% CV	2.3	3.0	2.1	1.8	2.7
LSD (0.05)	0.17	0.27	0.16	0.20	0.25

STB: Soil test-based inorganic fertilizers; CV: Coefficient of Variation; LSD: Least significant difference.

Table 5. Effect of different organic manures, rice straw and chemical fertilizer management on nutrient status of post-harvest soil after completion of five rice crops (0–15 cm soil depth).

Treatment	pH	Total N (g kg^−^1)	Available P (mg kg^−^1 soil)	Exchangeable K (c-mol kg^−1 soil)
Initial soil	5.85	0.90	22.0	0.13
Control	5.83	1.0	16.6	0.10
CD	6.20	2.0	35.3	0.24
PM	6.91	2.2	43.2	0.26
RS	6.00	1.6	26.0	0.28
STB	5.95	1.2	22.5	0.13
CV (%)	1.0	12.7	13.4	10.3
LSD (0.05)	0.12	0.03	7.23	0.13

Cont.: Control (no organic manure and chemical fertilizer); CD: Cow dung; PM: Poultry manure; RS: Rice straw; STB: Soil test-based fertilizers; organic matter was used at 2 ton carbon per hectare with IPNS-based chemical fertilizer; CV: Coefficient of variation; LSD: Least significant difference.

Figure 3. Variations of chemical properties under different treatments and soil depths of post harvest soil after completion of five rice crops: (a) soil organic carbon, (b) total nitrogen, (c) available phosphorus and (d) exchangeable potassium.