IJERD – International Journal of Environmental and Rural Development (2023) 14-1

Research article
erd

Effect of Bio-slurry and Chemical Fertilizer on Soil Enzyme
Activity
MOEURB ANG*
Faculty of Agricultural Engineering and Agronomy, Royal University of Agriculture,
Phnom Penh, Cambodia
Email: moeurb.ang@gmail.com

HONG CHEANG
Faculty of Agronomy, Royal University of Agriculture, Phnom Penh, Cambodia

DYNA THENG
Faculty of Agricultural Engineering, Royal University of Agriculture, Phnom Penh, Cambodia

NARETH NUT
Faculty of Agricultural Engineering, Royal University of Agriculture, Phnom Penh, Cambodia

LYHOUR HINBiogas Technology and Information Center and Faculty of Agricultural Engineering,
Royal University of Agriculture, Phnom Penh, Cambodia

LYTOUR LOR
Biogas Technology and Information Center and Faculty of Agricultural Engineering,
Royal University of Agriculture, Phnom Penh, Cambodia

KASUNI H. H. GAMAGE
Department of Agronomy, Kansas State University, Manhattan, Kansas, U.S.A

GANGA M. HETTIARACHCHI
Department of Agronomy, Kansas State University, Manhattan, Kansas, U.S.A
Received 22 April 2023

Accepted 30 May 2023(*Corresponding Author)

Abstract Organic nutrient sources are an effective way to improve soil fertility and increase
crop yield. Bio-slurry provides tremendous nutrient potential for the vegetative andreproductive growth of field crops and its long-term sustainability. Application of the bioslurry on the field can help to reduce fertilizer use, maintain productivity, and improve soil
health. Soil enzyme activity was enhanced by swine slurry. Enzyme activity following
fertilization takes precedence over microbial biomass in the short term. The study aimed (1)to study the effect of bio-slurry and chemical fertilizer on soil enzymes activity, and (2) tocompare the biomass growth of corn using bio-slurry and chemical fertilizer. The research wasconducted from November to December 2022 at the Throckmorton Plant Sciences Center,Department of Agronomy, Kansas State University, United States. The experiment wasconducted in pots under greenhouse conditions with 5 treatments, including Treatment 1:Control (without fertilizer), Treatment 2: bio-slurry, Treatment 3: urea, Treatment 4: NH4NO3
and Treatment 5: KNO3+NaNO3. Each treatment was conducted in 3 replications with 1 pot
per replication and 2 seeds per pot. The activities of soil enzymes, biomass of corn above
ground and root were collected and analyzed. Corn plants treated with bio-slurry and inorganic
fertilizer were found to have a non-significant growth of corn soil β-glucosidase enzyme with
4.41 mg/L, 3.83 mg/L, 4.23 mg/L, 4.11 mg/L, and 4.14 mg/L, respectively. With regard toaboveground and belowground biomass, no significant differences between the control andother treatments were observed. The results showed that bio-slurry released low amounts ofenzyme activity to the soil and provided good growth conditions to corn.
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Keywords crop, corn, slurry, soil fertility, soil health

INTRODUCTIONCorn (Zea mays L.) is the most vital cereal worldwide (Ka et al., 2022). USA, China, and Brazil contribute
63% of the global corn production while Mexico, Argentina, India, Ukraine, Indonesia, France, Canadaand South Africa are also major corn-producing countries (FAO, 2010). In Cambodia, commercial pig
farms have increased due to their ability to control the environment necessary for fast pig growth andeffective disease prevention (MAFF, 2019). Daily wastewater generated from the pig farm depends on
the type of pigs such as sows, fatteners, and piglets at 64 m3/head, 24 m3/head, and 20 m3/head,respectively (Kulpredarat, 2016).
Bio-slurry is a by-product of anaerobic digestion. The bio-slurry contains 93% water and 7%
dry matter, of which 4.5% is organic matter and 2.5% inorganic matter, easily available plant
nutrients, and high amount of nutrients and micronutrients. Total nitrogen, total phosphorus, andpotassium were 2.1%, 1.1%, and 0.98% and micronutrients like Fe, Cu, Mn, and Zn were 0.34 ppm,0.004 ppm, 0.088 ppm, and 0.023 ppm respectively. It's can be used as fertilizer directly or addedwith other organic materials on crops. (Kumar et al., 2015).
Soil enzymes are produced by animal manure, plants, and microorganisms. They areprominently secreted by microbes and stimulate microbial activity in this biome (Chernysheva et al.,2021). Soil microorganisms mainly synthesize extracellular enzymes such as β-glucosidase,hydrolases urease, phosphatase, glycosylating enzymes, and many more. Soil enzymes play a vitalrole in the biodegradation of organic compounds in soil and become the most delicate indicator ofchange in microbial activities that occur in the soil environment (Hueso et al., 2012).

OBJECTIVE
The objectives of the study were to determine study the effect of bio-slurry and chemical fertilizer
on soil enzyme activities and to compare the biomass growth of corn using bio-slurry and chemicalfertilizer.
METHODOLOGY
The experiment was conducted at Throckmorton Plant Sciences Center, Faculty of Agronomy,Kansas State University, The United States (39°11'37.3"N 96°35'04.2"W), during the autumn from
November to December 2022. DKC59-82RIB corn variety was used and planted in pots ingreenhouse condition. The experimental plots were followed a completely randomized design (CRD)with five treatments and 3 replications. The treatments were T1 (control), T2 (bio-slurry), T3 (urea),
T4 (NH4NO3), and T5 (KNO3+NaNO3). Recommended doses of fertilizer applied for corn were 190,30, and 100 kg/ha for N, P, and K, respectively. The soil was watered before planting the seeds,
following maximum water holding capacity (MWHC) equivalent to 1 liter of water per pot.
The bio-slurry was collected from the College of Civil Engineering, at KSU, and used swine
manure as substrate. Four samples, each about 1 kg of bio-slurry, were taken for nutrient content
analysis. The samples contained 957.72 mg/L TN, 43.71 mg/L TP, 598.74 mg/L TP, 120.50 mg/L,
22.68 mg/L Mg, 12.13 mg/L S, and micronutrients (0.10 mg/L Al, 0.37 mg/L Fe, and 152.49 mg/LNa) (Kansas State Soil Testing Lab., 2022)
Soil samples were taken from two locations in each pot at the depth of 0-5 cm at 3 weeks after
planted and transported back to the laboratory in plastic trays. For enzymatic analysis, 1-g of the wet
soil was mixed with 1 mL of p-Nitrophenyl-β-D-glucosidase (PNG) solution, 4 mL MUB at pH 6.0-,
and 0.25-mL toluene. The solution was hand-shaken slowly a few seconds, capped, and then placedin the incubator for 1 hour at 37 0C. Afterwards, the sample was withdrawn, cooled down at the room
temperature, and then added with 1 mL of 0.5M CaCL2 and 4 mL of 0.1M THAM buffer pH 12. Thissecond mixture was hand-shaken for another few seconds and then poured into a beaker through apaper filter Watman No. 2. Before the prepared soil solution was tested in the spectrophotometer,Ⓒ ISERD

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this equipment had to be first tested with six levels of pre-prepared solutions to verify its accuracy.
Those solutions contained p-nitrophenol diluted solutions of 0, 1, 2, 3, 4, and 5 mL; six levels ofwater in reverse order from 5 to 0 mL; each 1 mL of CaCl2; and each 4 mL of THAM pH 12. Afterthe accuracy was verified, the soil samples were then analyzed using this equipment. (Eivazi andTabatabai, 1978). Values were corrected for a blank (Substrate added immediately after the additionof CaCL2 and Tris NaOH) and for adsorption of released para-nitrophenol 𝜌𝑁𝑃 in the soil (Vuorinen,1993). β-glucosidase activity is expressed as 𝜇𝑚𝑜𝑙 𝜌𝑁𝑃 𝑟𝑒𝑙𝑒𝑎𝑠𝑒𝑑 𝑔−1 dry soil ℎ−1.
Each soil was air-dried 24 hours. Afterwards, the dried soil was ground and sieved to obtain soil
particles of less than 2 mm for soil pH, soil moisture content, and plant nutrients analysis. Soil pH
was determined using ORION Star A11 Bench top pH meter with a soil-water ratio of 1:10 (Bruceet al., 1982). Soil moisture content was calculated by subtracting the weight of the dry soil, ovendried at 105 0C for 48 hours until it reached a constant weight.
Two kinds of corn biomass were measured four weeks after planting. Aboveground biomass
was collected by cutting all corn stems in each pot from the stem base, then oven-dried at 60 0C for
72 hours and weighed. Underground biomass was collected by separating the soil clods and brushing
the roots gently before soaked in distilled water to ensure that all soil was removed. Then, clean roots
were oven-dried at 60 0C for 72 hours and weighed.
RESULTS AND DISCUSSION
Soil Enzyme (β-glucosidase)In terms of β-glucosidase activity, there were no significant differences among the treatments (Table1). On the other hand, the mean concertation of β-glucosidase in soil was found to decrease among
grand mean of 4.13 𝜇𝑚𝑜𝑙 𝜌𝑁𝑃 (Table 1)
Table 1 Effect of different fertilizer on Soil enzyme activity
Mean (𝜇𝑚𝑜𝑙 𝜌𝑁𝑃)
4.33
3.83
4.23
4.11
4.14
4.13
0.08
0.69

Treatments
Control
Bio-slurry
Urea
NH4NO3
KNO3+NaNO3Grand mean
SEPr (>F)
Source: Kansas State Soil Testing Lab., 2022

Fig. 1 Competition of corn aboveground biomass in different treatmentsⒸ ISERD136

IJERD – International Journal of Environmental and Rural Development (2023) 14-1

Soil Moisture Content
The result showed no significant difference among the treatments (P > 0.05). We were able tomaintain the soil moisture evenly among the treatment (Table 2). In terms of aboveground biomass,
it was observed that there are no significant differences between the control and the other treatmentswith reactions of 10.1%, 9.20%, 8.90% and 8.70%, respectively (Fig. 1; P > 0.05). However,
aboveground biomass of swine slurry treatment was higher than others.
No significant differences in the underground biomass were observed between the control andother treatments (P > 0.05), with reduction of 20.10%, 20.60%, 22.07%, and 21.50% for the swine
slurry, urea, NH4 NO3 and KNO3 + NaNO3 treatments, respectively (Fig. 2).
Table 2 Effect of different fertilizer on Soil moisture
Treatment
Control
Bio-slurry
Urea
NH4NO3
KNO3 + NaNO3

Mean (%)
2.71
2.63
2.79
2.65
2.68

SD
0.08
0.08
0.21
0.08
0.11

Kansas State Soil Testing Lab (2022)

Fig. 2 Underground biomass
CONCLUSION
The results of this research demonstrated that swine slurry treatment cannot affect to soil enzyme
activity (β-glucosidase), aboveground biomass, and underground biomass for a short term.
According to the results obtained in this study, it is proposed to continue studying the soil enzyme
activities for a long term and Phospholipid fatty acid (PLFA).
ACKNOWLEDGEMENTS
The authors would like to express our sincere thanks to the Higher Education Improvement Project(HEIP) funded by World Bank via Royal University of Agriculture (RUA) for financial support andThrockmorton Plant Sciences Center, Department of Agronomy, Kansas State University (KSU) forthe laboratory and facilities.
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