Proceedings Biodigester Workshop March 2002

http://www.mekarn.org/procbiod/choke.htm

Utilization of fermented slurry as bio-fertilizer

Choke Mikled, Suchart Jiraporncharoen^*and Nirandorn Potikanond

Department of Animal Science
* Department of Soil Science and Conservation,
Faculty of Agriculture, Chiang Mai University,
Chiang Mai 50200, Thailand
agani008@chiangmai.ac.th

Abstract

Fermented slurry (FS) sometimes called bio-slurry, as a by-product of the anaerobic fermentation of animal excrements in the biogas digester, is an excellent organic fertilizer which can make and important contribution to better crop yield and lasting soil fertility.

Various experiments were carried out to study the efficient use of fermented slurry (FS) as fertilizer for crop production. The results showed that fermented slurry could be used solely or used together with chemical fertilizer at different ratios for rice and vegetables. The results from using FS at different levels for baby corn and Napier grass from the 2-years experimental period showed a tendency for higher yields and nutritive values in comparison with the application of chemical fertilizer. It is also worth to mention that the FS as bio-fertilizer could play an important role in soil fertility improvement.

Key words: Biodigester, slurry, effluent, fertilizer, crops

Introduction

Fermented slurry, sometimes called bio-slurry, as a product of anerobic fermentation of animal excrements in the biogas digester, is an excellent organic fertilizer which can make an important contribution to better crop yields and lasting soil fertility. The fermented slurry which contains relatively high percentage of readily available nutrients, can be directly applied in liquid form to the plants both for basal and top-dressing, in a dried form and also for compost preparation together with other organic material.

Chemical composition of fermented slurry

Nitrogen is an important element for crop growth. The nitrogen in animal manure is normally available in an organic form but after passing through the fermentation process in a biogas digester it is changed (by bacteria) to inorganic form mostly ammonia nitrogen (NH₄⁺) which is easily soluble and utilized by crop plants. The chemical composition of fermented slurry from pig manure in a liquid form is shown in Table 1.

Table 1: Chemical composition (% fresh basis) of fermented slurry from pig manure
pH	7.8
Water	86.2
Dry matter	13.8
Nitrogen (N)	0.37
Phosphorus (P)	0.35
Potassium (K)	0.21
Source : Sanmaneechai et al (1992)

Utilization of fermented slurry as fertilizer for crops

Fermented slurry over-flowed from the outlet of the biogas digester can be readily utilized and applied directly to crop plants in a liquid form. This is the best method to apply fermented slurry to crops such as fodder grass, fruit trees or vegetables. Nevertheless, in most cases the fermented slurry could be dried up through sand bed filter and sold out from the farms in dry form.

Utilization of fermented slurry (FS) as fertilizer of cereal crops

The studies of Sanmaneechai et al (1992) at the Chiang Mai University Farm showed that in the treatments by application of FS alone or FS plus chemical fertilizer could increase the organic matter and phosphorus contents in the soil. In the treatment that only applied FS, the rice yield was 3,881 kg/ha which was 24.4 percent higher than the no fertilizer plot. The chemical fertilizer plot gave 1,081 kg more than the FS only plots in the first year of the experiment. In the same experiment, it was also shown that the application of FS plus chemical fertilizer at the ratios of 50 : 50 and 25 : 75 to the rice plots could produce the same yield as the solely chemical fertilizer plot. In the following rice cropping without any application of fertilizer, the residual effects form the first cropping showed that in the FS plot still gave about 79 percent higher yield than no fertilizer plot but lower than the chemical fertilizer plot.

Utilization on of fermented slurry (FS) as fertilizer for vegetables

The same group of researchers (Sanmaneechai et al 1992) also studied using a mixture of FS and chemical fertilizer at different ratios with chinese cabbage and kale. It was shown that in the no fertilizer plot, chinese cabbage could not grow well and produced only about 3,556 kg/ha which was about 4.8 times less yield than that of the FS plot but still less yield than the only chemical fertilizer plots. For kale, the FS plot gave about 4.7 times more yield than the no fertilizer plot and even more than the only chemical fertilizer plot.

Utilization of fermented slurry as fertilizer for baby corn and Napier grass

Mikled et. al (1994) studied use of fermented slurry (0.09ą0.04 % N) as liquid fertilizer for baby corn (field crops) and Napier grass (forage crops) at different rates as compared to chemical fertilizer. The results of the two experiments are shown as follows. The treatments in the experiment with baby corn were: control (no fertilizer), CF120 (chemical fertilizer at 120 kg N/ha), FS 120 (fermented slurry 120 kg N/ha) and FS 180 (fermented slurry 180 kg N/ha). The experiment was run for two years with 10 crops (5 crops each year). The measurements were concentrated mainly on baby corn yields, corn stover yields and nutritive value. In Thailand, the advantages for the farmers to grow baby corn are to harvest the young ear corn and sell to the market as vegetable and to cut the stover and feed to the cattle as roughage. From Table 2 and 4 it can be seen that baby corn yields and baby corn stover from chemical fertilizer was higher than other treatments for only the first two crops but, towards the end of the first year and throughout the second year, all FS treatments could produce at about the same yield or even higher at the higher levels of FS.

Table 2: Baby corn yield (kg/ha) in the first year (Numbers within the same column not followed by the same letter are different at P<0.05).
	Crop Number					Average
	1	2	3	4	5	Average
Control	3312^b	909^c	250^c	3076^c	2590^b	2027
CF 120	5805^a	3326^a	2507^b	5888^a	6076^a	4720
FS 60	3076^b	1652^b	902^c	4083^bc	4416^a	2826
FS 120	2486^b	1622^b	2902^b	5590^ab	5062^a	3530
FS 180	3257^b	2243^b	5083^a	6361^a	6062^a	4601
Mean	3587 NS	1948*	2329**	5000*	4841**

Table 2 (cont.): Baby corn yield (kg/ha) in the second year (Numbers within the same column not followed by the same letter are different at P<0.05).
	Crop Number					Average
	6	7	8	9	10	Average
Control	1562^e	1451^d	1444^c	1451^c	1666^d	1515
CF 120	6715^b	4250^bc	4757^b	3361^bc	5104^c	4837
FS 60	4395^d	3583^c	4840^b	5486^ab	6479^b	4957
FS 120	6034^c	5541^b	6729^a	6958^a	7903^a	6633
FS 180	8812^a	7368^a	7875^a	7111^a	8847^a	8000
Mean	5504**	4438**	5129**	4873**	6000**

The average baby corn and stover yields from both years were substantially similar to other reports (Lekhakul 1988; Sompong 1988; Ruangsiri 1990). However, in the long run by application of FS the tendency of higher yield of baby corn would be more prominent without any detrimental effect on soil fertility (see later in the part of soil properties). The types and rates of N fertilizer affected the chemical compositions of the baby corn stover (Table 3) especially the crude protein content, as at the higher rate of N fertilizer showed the tendency of higher crude protein value.

Table 3: Average chemical composition of baby corn stover from 10 cropping periods.
Treatments	DM %	% of DM
Treatments	DM %	OM	CP	EE	CF	NFE
Control	24.96	94.44	3.92	1.91	28.96	59.58
	(ą2.46)	(ą1.66)	(ą0.73)	ą0.34	ą2.47	ą3.18
CF 120	25.39	95.27	5.26	2.13	30.43	57.44
	(ą3.52)	(ą1.01)	(ą1.86)	ą0.37	ą2.53	ą4.17
FS 60	25.20	94.60	4.39	2.10	29.99	58.13
	(ą2.85)	(ą0.78)	(ą0.88)	ą0.52	ą2.52	ą3.33
FS 120	25.02	94.85	5.41	2.05	30.57	56.75
	(ą2.56)	(ą0.96)	(ą1.50)	ą0.46	ą2.55	ą3.75
FS 180	24.54	94.32	6.03	2.24	29.94	56.10
	(ą2.40)	(ą0.54)	(ą2.18)	ą0.39	ą2.30	ą3.80
Mean	25.02	94.70	5.00	2.09	29.98	57.60
	ą0.32	ą0.38	ą0.84	ą0.12	ą0.63	1.34

Table 4: Dry matter yield (kg/ha) of baby corn stover in the first year
	Crop Number					Total
	1	2	3	4	5
Control	2057^b	1036^b	1067^b	3066^d	2074^b	6,541
CF 120	4758^a	2011^a	2383^ab	5201^a	3660a	18,015
FS 60	2297^b	1187^b	1395^b	3616^c	2901^ab	11,397
FS 120	1818^b	1205^b	1868^ab	4542^b	3300^ab	12,735
FS 180	2226^b	1470^b	2643^a	5326^a	3987^a	15,652
Mean	2631	1382	1871	4350	3184
	**	**	*	**	NS

Table 4 (cont.): Dry matter yield (kg/ha) of baby corn stover in the second year
	Crop Number					Total
	1	2	3	4	5
Control	1125.0^d	1630.2^c	1654.7^c	1367.4^b	1671.7^c	7,449.0
CF 120	4007.1^ab	3193.8^b	3306.8^b	2450.9^ab	3087.6^b	16,046.2
FS 60	2383.0^c	2861.7^b	3115.3^b	3612.5^a	3699.8^b	15,672.3
FS 120	3464.0^b	3306.7^b	3900.2^b	4283.5^a	5277.1^a	20,231.5
FS 180	4503.6^a	4750.1^a	4920.4^a	4216.9^a	5775.5^a	24,165.5
Mean	3096.5	3148.5	3379.5	3186.0	3898.4
	**	**	*	**	**

In the experiment with Napier grass, the treatments were: Control (no fertilizer), CF 150 (150 kg N/ha from chemical fertilizer), FS 75 (75 kg N/ha from FS), FS 150 (150 kg N/ha from FS) and FS 225 (225 kg N/ha from FS). The experiment was run also for two consecutive years with 16 cuttings (8 cuttings each year). The dry matter yield of Napier grass and total production are shown in Table 5 and 5.1. After a few cuttings the tendency of higher yield from the FS treatments at the same and higher rates in comparison with chemical fertilizer were prominent. The yield of Napier grass in the second year was somewhat lower than the first year due to the reduction of N level to only one-fifth of the actual rate of each fertilizer treatment.

Table 5: Dry matter production of Napier grass in the first year (November 1990 - November 1991) (kg ha^-1)
	Cutting Number								Total
	1	2	3	4	5	6	7	8	Total
Control	2419.3^a	1795.5^a	2833.5a^b	3700.9^a	4090.8^b	3104.3^a	1353.6^a	1690.6^a	20,988.5
CF 150	2212.8^a	3364.1^a	2341.9^a	4792.6^a	4069.2^b	3618.9^a	1065.3^a	1876.8^a	23,341.6
FS 75	2280.4^a	1375.0^a	1686.5^b	4992.6^a	4693.0a^b	3613.5^a	1436.0^a	2527.0^a	22,604.0
FS 150	1840.4^a	2761.8^a	2129.8^ab	7280.7^a	5335.7a^b	3272.0^a	1538.8^a	2148.9^a	26,308.1
FS 225	2346.3^a	2138.6^a	4471.1^ab	6331.0^a	7062.4^a	5806.0^a	1535.9^a	2206.6^a	31,903.9
Mean	2219.8	2287.0	2693.8	5419.6	5050.2	3883.0	1385.9	2090.0
	NS	NS	NS	NS	NS	NS	NS	NS

Table 5.1: Dry matter production of Napier grass in the second year (December 1991-December 1992) (kg ha-1)
	Cutting Number								Total
	9	10	11	12	13	14	15	16	Total
Control	1012.7^a	924.1^{a b}	1489.0^c	1429.4^c	1339.3^c	1246.8^bc	852.7^c	658.3^c	8,952.3
CF 150	1263.3^a	1440.1^ab	1620.1^bc	1611.4^bc	1746.6^bc	995.0^c	779.4^c	905.4^c	10,361.3
FS 75	823.0^a	688.3^b	1801.4^bc	1805.0^bc	1806.7^bc	1392.7^bc	1092.2^bc	1198.9^bc	10,608.2
FS 150	1395.7^a	1477.2^ab	1477.2^ab	3125.7^ab	2076.1^ab	2396.2^ab	1778.0^ab	1797.0^ab	15,494.4
FS 225	1241.1^a	1830.5^a	3904.1^a	2615.5^a	2837.3^a	2221.7^a	1545.8^a	2413.2^a	18,609.2
Mean	1147.2	1272.0	2388.1	1907.5	2025.2	1526.8	1143.7	1394.6
	NS	NS	NS	NS	NS	NS	NS	NS

The nutritive value of Napier grass is shown in Tables 6.1, 6.2 and 6.3. The average percentage of crude protein (CP) content of Napier grass was highest in the CF 150 plot only in the first year but in the second year was highest in the FS 225 plot. The CP content in the FS 150 and FS 225 plots in the first year was about the same, but in the second year a tendency of higher CP contents in FS 225 plot was pronounced, probably due to the deposition and the availability of N from fermented slurry in the soil.

Table 6.1: Average chemical composition of Napier grass in the first year.
	Dry matter %	% of dry matter
	Dry matter %	OM	CP	EE	CF	NFE
Control	18.83	85.02	6.91	2.82	21.43	42.84
	(ą4.01)	(ą1.72)	(ą1.21)	ą0.23	ą1.66	ą2.74
CF 150	19.70	87.68	8.14	2.85	32.52	44.30
	(ą2.43)	(ą1.28)	(ą2.05)	ą0.37	ą2.10	ą2.91
FS 75	18.98	86.04	6.96	2.93	32.74	43.39
	(ą4.28)	(ą2.10)	(ą1.47)	ą0.36	ą1.69	ą2.44
FS 150	18.61	88.69	7.78	3.05	32.80	42.44
	(ą2.72)	(ą1.11)	(ą1.40)	ą0.49	ą1.69	ą2.55
FS 225	17.93	85.89	7.71	3.08	32.15	42.95
	(ą1.74)	(ą1.85)	(ą1.26)	ą0.50	ą2.49	ą2.79
Mean	18.81	86.26	7.50	2.95	32.53	43.18
	ą0.64	ą0.99	ą0.54	ą0.12	ą0.26	ą0.71

The fertilizer treatments did not effect the crude fibre content of Napier grass from both years. Surprisingly, the mean crude fibre content in the second year was lower than that in the first year (32.53% vs 30.78%). An average crude fibre content of Napier grass from both year was 31.65%.

Table 6.2: Average chemical composition of Napier grass in the second year
Treatments	Dry matter %	% of dry matter basis
Treatments	Dry matter %	OM	CP	EE	CF	NFE
Control	19.74	85.13	7.27	3.44	30.55	43.87
	(ą3.52)	(ą3.14)	(ą0.64)	ą0.87	ą2.12	ą2.12
CF 150	20.55	86.89	7.76	3.40	30.30	45.44
	(ą3.96)	(ą2.10)	(ą0.88)	ą0.87	ą2.05	ą1.88
FS 75	19.93	85.86	7.63	3.40	30.71	44.05
	(ą3.80)	(ą2.71)	(ą0.85)	ą0.71	ą1.64	ą1.47
FS 150	19.79	86.81	7.97	3.52	31.38	43.66
	(ą2.81)	(ą1.98)	(ą0.93)	ą0.71	ą0.94	ą1.80
FS 225	19.55	86.72	8.35	3.49	30.96	43.93
	(ą2.03)	(ą1.83)	(ą1.68)	ą0.89	ą0.98	ą3.07
Mean	19.91	86.28	7.80	3.45	30.78	44.19
	ą0.38	ą0.76	ą0.39	ą0.05	ą0.41	ą0.71

Table 6.3: Average chemical composition of Napier grass for the whole period of the experiment.
	Dry matter %	% of dry matter basis
	Dry matter %	OM	CP	EE	CF	NFE
Control	19.28	85.07	7.09	3.13	31.49	43.35
CF 150	20.12	87.28	7.95	3.12	31.41	44.87
FS 75	19.45	85.95	7.29	3.16	32.09	43.72
FS 150	19.20	86.75	7.87	3.28	31.55	43.05
FS 225	18.74	86.30	8.03	3.28	30.96	43.44
Mean	19.36	86.27	7.65	3.20	31.65	43.68

Changes of soil fertility by fermented slurry

The chemical analysis of soil samples taken from every cropping of baby corn and from every cutting of Napier grass in both experiments is illustrated in Tables 7 and 8. The results of chemical analysis for pH, organic matter content, total-N, extractable-P, K and S of the two years experimental periods are summarized as follows:

There was only a little effect of fermented slurry on the change in soil pH as compared with control. The reduction of soil pH due to the continuous application with chemical fertilizer is distinct.

It is clear that the accumulation of organic matter content of soil is in relation to the rate of FS applies.

The build-up of total N, extractable P and S is also pronounced in accordance with the rate of FS applied. In this case, the most benefit from the use of FS is high N uptake, high N retention in soil and less loss in comparison with chemical fertilizer.

Conclusions

It may be concluded that FS plays an important role as bio-fertilizer in soil fertility improvement. It shows a tendency of better effect in crop production when applied at the same rate as chemical fertilizer.

Table 7: Changes in some chemical properties of soil planted to baby corn as affected by chemical fertilizer or fermented slurry application.
				Extractable
	pH	OM	Total-N	P	K	S
		%			ppm
Before planting	6.1	1.39	0.068	20.5	50.5	4.3
After two years
Control (No-N)	6.1	1.48	0.072	26.0	34.4	11.6
CF 120	5.4	1.50	0.073	58.8	35.6	13.2
FS 60	6.1	1.78	0.076	156.3	38.8	18.7
FS 120	6.1	1.96	0.081	164.4	41.3	22.0
FS 180	6.2	2.29	0.083	192.4	36.9	29.7

Table 8: Changes in some chemical properties of soil planted to Napier grass as affected by chemical fertilizer or fermented slurry application
				Extractable
	pH	OM	Total-N	P	K		S
		%				ppm
Before planting	6.7	1.40	0.068	11.7		100.6		7.8
After two years
Control (No-N)	6.4	1.65	0.083	14.5		28.3		11.5
CF 150	6.2	1.80	0.084	15.5		31.3		13.2
FS 75	7.0	1.86	0.085	52.5		33.8		13.2
FS 150	7.1	2.12	0.089	69.7		35.7		14.8
FS 225	7.0	2.17	0.094	98.9		40.0		15.4

References

Lekhakul T 1988 Future of baby corn industry In : Corn Industry, Corn and Sorghum Research Centre, Kasetsart University, Bangkok pp 45-49.

Mikled C, Jiraporncharoen S and Potikanond N 1994 Fermented Slurry as fertilizer for the production of forage crops. Final Report, Thai-German Biogas Programme.

Ruangsiri T 1990 Utilization of baby corn wastes in feed-lot feeding of Holstein Friesian crossbred bulls. Master Degree Thesis, Kasetsart University, 65 pp.

Sanmaneechai M, Insomphan S, Phuekpong B, Knacharoenpong A and Kornisaranukul P 1992 Utilization of fermented slurry as fertilizer for crops. Proc. Conf. Biogas in Thailand Present and Future Perspective, Thai-German Biogas Programme (GTZ), Chiang Mai, Thailand (27-28 February, 1992).

Sompong S 1988 Baby corn production. In : Corn Industry, Corn and Sorghum Research Centre, Kasetsart University, Bangkok, pp 18-43.