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. 

 

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 (0.09±0.04 % 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 (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
Control	1562e	1451d	1444c	1451c	1666d	1515
CF 120	6715b	4250bc	4757b	3361bc	5104c	4837
FS 60	4395d	3583c	4840b	5486ab	6479b	4957
FS 120	6034c	5541b	6729a	6958a	7903a	6633
FS 180	8812a	7368a	7875a	7111a	8847a	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
		OM	CP	EE	CF	NFE
Control	24.96	94.44	3.92	1.91	28.96	59.58
	(±2.46)	(±1.66)	(±0.73)	±0.34	±2.47	±3.18
CF 120	25.39	95.27	5.26	2.13	30.43	57.44
	(±3.52)	(±1.01)	(±1.86)	±0.37	±2.53	±4.17
FS 60	25.20	94.60	4.39	2.10	29.99	58.13
	(±2.85)	(±0.78)	(±0.88)	±0.52	±2.52	±3.33
FS 120	25.02	94.85	5.41	2.05	30.57	56.75
	(±2.56)	(±0.96)	(±1.50)	±0.46	±2.55	±3.75
FS 180	24.54	94.32	6.03	2.24	29.94	56.10
	(±2.40)	(±0.54)	(±2.18)	±0.39	±2.30	±3.80
Mean	25.02	94.70	5.00	2.09	29.98	57.60
	±0.32	±0.38	±0.84	±0.12	±0.63	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	2057b	1036b	1067b	3066d	2074b	6,541
CF 120	4758a	2011a	2383ab	5201a	3660a	18,015
FS 60	2297b	1187b	1395b	3616c	2901ab	11,397
FS 120	1818b	1205b	1868ab	4542b	3300ab	12,735
FS 180	2226b	1470b	2643a	5326a	3987a	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	1125.0d	1630.2c	1654.7c	1367.4b	1671.7c	7,449.0
CF 120	4007.1ab	3193.8b	3306.8b	2450.9ab	3087.6b	16,046.2
FS 60	2383.0c	2861.7b	3115.3b	3612.5a	3699.8b	15,672.3
FS 120	3464.0b	3306.7b	3900.2b	4283.5a	5277.1a	20,231.5
FS 180	4503.6a	4750.1a	4920.4a	4216.9a	5775.5a	24,165.5
Mean	3096.5	3148.5	3379.5	3186.0	3898.4