Effects of Biogas Slurry Instead of Chemical Fertilizer on Soil
Nutrients and Maize Growth
Yongcheng Liu
1a
, Fucheng Li
1,*
, Yue Hu
1b
, Bo Mei
2,c
and Lu Feng
1,d
1
School of Resource & Environment, Southwest University of Science and Technology, Mianyang 621010, China
2
Sichuan Xuebao Dairy Group Co Ltd, Mianyang 621010, China
Keywords: Biogas Slurry, Organic Fertilizer, Soil Nutrient, Maize Growth.
Abstract: In order to explore the best ratio of chemical fertilizer and biogas slurry in the process of biogas slurry
returning to the field, experiments were carried out with different fertilization methods such as different
proportion of biogas slurry replacing chemical fertilizer and whether topdressing or not. When the
proportion of biogas slurry instead of chemical fertilizer was 60% to 70%, the weight of per plant and leaf
of maize reached the maximum value, which were 1064.37g and 959.13g, respectively. When the proportion
of biogas slurry replacing chemical fertilizer were 60% to 70%, the content of available phosphorus was the
highest. The content of soil total nitrogen, ammonium nitrogen and nitrate nitrogen was the highest when
the proportion of biogas slurry replacing chemical fertilizer was 80%, and the content of soil alkali
hydrolyzable nitrogen was the highest when the proportion of biogas slurry replacing chemical fertilizer was
70%. In terms of the yield of silage corn and the content of soil nutrients, and the effect is the best when the
proportion of biogas slurry instead of chemical fertilizer was between 60% and 80%.
1 INTRODUCTION
1
Chinese government attaches great importance to the
development of agricultural circular economy,
recycling agricultural wastes, reducing the use of
chemical fertilizers and protecting the environment,
among which biogas project is the most typical
example. Biogas slurry, as a by-product of rural
biogas project, can provide fertilizer for crop
growth, which is essential for the healthy and
long-term development of rural areas. The
comprehensive application of biogas slurry and
chemical fertilizer provides higher grain yield and
economic profitability (Ferdous 2020). As far as
heavy metal pollution is concerned, it is safe and
sustainable to apply appropriate amount of biogas
slurry to farmland (Tang 2020). Excessive use of
biogas slurry will adversely affect crops and increase
the risk of environmental pollution (Chen 2017).
Therefore, the purpose of this paper was to further
determine the application amount of biogas slurry
a
https://orcid.org/0000-0001-7712-9548
b
https://orcid.org/0000-0001-9726-3066
and the ratio of chemical fertilizer to biogas slurry in
the process of biogas slurry returning.
2 MATERIALS AND METHODS
2.1 Experimental Materials
In this pot experiment, the soil is purple soil. Round
flower pots with a diameter of 30 cm and a height of
25 cm were selected for the experiment, and each
pot was filled with about 8.5 kg of air-dried soil,
keeping the depth of the soil layer at 20 cm. Maize is
a conventional variety. Biogas slurry was taken from
Sichuan Xuebao Dairy Group Co Ltd. The nutrient
content of the biogas slurry is 1.04 g kg-1 of
nitrogen, 0.50 g kg-1 of phosphorus and 0.93 g kg-1
of potassium. Urea contained 46% nitrogen (N),
potassium dihydrogen phosphate contained 24%
phosphorus pentoxide (P
2
O
5
) and 27% potassium
oxide (K
2
O), and potassium chloride contained
62.7% potassium oxide (K
2
O). The basic properties
of soil samples in this test is presented in Table 1.
116
Liu, Y., Li, F., Hu, Y., Mei, B. and Feng, L.
Effects of Biogas Slurry Instead of Chemical Fertilizer on Soil Nutrients and Maize Growth.
DOI: 10.5220/0011189600003443
In Proceedings of the 4th International Conference on Biomedical Engineering and Bioinformatics (ICBEB 2022), pages 116-121
ISBN: 978-989-758-595-1
Copyright
c
 2022 by SCITEPRESS – Science and Technology Publications, Lda. All rights reserved

2.2 Experimental Design
According to the determined nitrogen application
rate, the biogas slurry and chemical fertilizer were
divided into 6 groups according to different
proportions. Each group was set with two different
fertilization methods. The first was to use 60%
nitrogen fertilizer as base fertilizer and 40% nitrogen
fertilizer as topdressing. The second was to use
100% nitrogen fertilizer as base fertilizer and
phosphorus and potassium fertilizer as base fertilizer
at the same time. There were 12 treatments in total.
The target yield of dry grain of silage maize is 7920
kg ha-1, and the total application amount of fertilizer
is 203.55 kg ha
-1
of nitrogen (N), 68.10 kg ha
-1
of
phosphorus pentoxide (P
2
O
5
) and 169.5 kg ha
-1
of
potassium oxide (K
2
O). According to the fertilizer
content and potting area of different chemical
fertilizers, the amount of chemical fertilizer required
for each pot is calculated. Specific fertilization
amount in this test is presented in Table 2.
2.3 Determination Method
After 100 days of maize sowing, the physiological
characters of plants and basic soil properties were
measured. Plant physiological characters included:
ground leaf weight, root weight, plant height,
maximum stem circumference, number of leaves,
maximum leaf length and maximum leaf width. The
basic properties of soil included pH, moisture
content, total nitrogen, total phosphorus, organic
carbon, nitrate nitrogen, ammonium nitrogen, alkali
hydrolyzable nitrogen and available phosphorus. pH
was measured by potentiometric titration; Total
nitrogen was determined by automatic nitrogen
determinator; total P was determined by the sodium
hydroxide (NaOH) extraction method (Wang 2014);
Organic carbon was determined by potassium
dichromate external heating method; Ammonia
nitrogen was extracted with potassium chloride
solution and determined by spectrophotometry;
Available phosphorus was determined by Sodium
hydrogen carbonate solution-Mo-Sb anti
spectrophotometric method.
Table 1: Main nutrient content of potted soil.
Item Total nitrogen
(g kg
-1
)
Total phosphorus
(g kg
-1
)
Alkali hydrolyzed nitrogen
(mg kg
-1
)
Available phosphorus
(mg kg
-1
)
Soil organic
carbon (g kg
-1
)
value 0.91 0.70
86.22 22.61
9.94
Table 2 Different experimental treatments of biogas slurry instead of chemical fertilizer
Proportion
Fertilization
mode
Base fertilizer Topdressing
Potassium dihydrogen
p
hosphate(g)
Potassium
chloride(g)
Urea (g)
Biogas
slurry(mL)
Urea (g)
Biogas slurry
(mL)
100%
SF
0.979 0.423
0.000 694.72 0.000 463.15
SBN 0.000 1157.87
- -
80%
SF
1.084 0.612
0.282 555.75 0.188 370.50
SBN 0.470 926.25
- -
70%
SF
1.137 0.707
0.423 486.28 0.282 324.19
SBN 0.704 810.46
- -
60%
SF
1.190 0.802
0.564 416.81 0.376 277.87
SBN 0.939 694.68
- -
40%
SF
1.295 0.991
0.845 277.87 0.564 185.25
SBN 1.409 463.12
- -
20%
SF
1.401 1.181
1.127 138.94 0.751 92.63
SBN 1.879 231.56
- -
Note: SF represents split fertilization; SBN represents single basal application.
Effects of Biogas Slurry Instead of Chemical Fertilizer on Soil Nutrients and Maize Growth
117

3 RESULTS AND DISCUSSION
3.1 Effects of Different Proportions of
Biogas Slurry and Chemical
Fertilizer on Nutrients
In the staged fertilization method, with the increase
of the proportion of biogas slurry replacing chemical
fertilizer, the soil total phosphorus content first
increased and then decreased, reaching the
maximum when the proportion of biogas slurry
replacing chemical fertilizer is 70%, while in the
one-time fertilization method, the soil total
phosphorus content is relatively high in the
treatment of 20% and 80% of biogas slurry replacing
chemical fertilizer (Fig. 1a), and there is no
significant difference in other treatments. In both
fertilization methods, the content of available
phosphorus first increased and then decreased with
the increase of the proportion of biogas slurry
replacing chemical fertilizer. When the proportion of
biogas slurry replacing chemical fertilizer was 60%
and 70%, the content of rapidly available
phosphorus was larger (Fig. 1b). Only when the
proportion of biogas slurry insteaded of chemical
fertilizer was 60% and 70%, the content of soil total
phosphorus was higher by split fertilization than by
one-time fertilization. The changes of soil available
phosphorus and soil total phosphorus were the same,
which indicated that under the proportion of 60%
and 70% biogas slurry instead of chemical fertilizer,
the content of soil total phosphorus and available
phosphorus increased by split fertilization.
With the increase of the proportion of biogas
slurry replacing chemical fertilizer, the contents of
soil total nitrogen, alkali hydrolyzable nitrogen,
ammonium nitrogen and nitrate nitrogen increased
first and then decreased. The contents of soil total
nitrogen, ammonium nitrogen and nitrate nitrogen
were the highest when the proportion of biogas
slurry replacing chemical fertilizer was 80%, while
the contents of soil alkali hydrolyzable nitrogen
were the highest when the proportion of biogas
slurry replacing chemical fertilizer was 70% (Fig.
1c). The difference of soil total nitrogen under the
two fertilization methods was not obvious (Fig. 1f).
The alkali hydrolyzable nitrogen shows that the
one-time fertilization method was greater than the
split fertilization method. When the ratio of biogas
slurry to chemical fertilizer was less than 70%,
one-time fertilization was greater than split
fertilization, while when the proportion of biogas
slurry to chemical fertilizer is high (80% and 100%),
one-time fertilization was less than split
fertilization(Fig. 1e). The characteristics of soil
nitrate nitrogen and soil ammonium nitrogen were
opposite (Fig. 1d), indicating that in fertilization
dominated by biogas slurry fertilizer, split
fertilizationis conducive to the accumulation of soil
ammonium nitrogen, while in the fertilization
dominated by chemical fertilizer, split fertilization
was conducive to the accumulation of nitrate
nitrogen. Biogas slurry partially substituting
chemical fertilizer could significantly improve soil
fertility, including available nitrogen, phospho-rus,
and potassium (Wang 2019). This is consistent with
our research.
3.2 Effects of Different Proportions of
Biogas Slurry and Chemical
Fertilizer on Maize Growth
With the increase of the proportion of biogas slurry
instead of chemical fertilizer, the weight of corn per
plant and leaf weight first increased and then
decreased under the two fertilization methods, both
of which are larger in the proportion of biogas slurry
instead of chemical fertilizer of 60% and 70% (Fig.
2a, b). When the ratio of biogas slurry to chemical
fertilizer was not more than 70%, the weight of
single plant and leaf of maize under one-time
fertilization was greater than that under split
fertilization. Under the treatment with higher ratio of
biogas slurry to chemical fertilizer, the weight of
single plant and leaf of Maize under split
fertilization was greater than that under one-time
fertilization. Under the condition of ensuring the
same total amount of fertilization, when the
proportion of biogas slurry application was
relatively low, the effect of one-time fertilization
was better than that of split fertilization. When the
proportion of biogas slurry application increased to
more than 80%, the effect of split fertilization was
better than that of one-time fertilization. This is
because biogas slurry belongs to liquid fertilizer, and
most nutrients belong to water-soluble and available
state. After one-time fertilization, nutrients may be
lost with runoff; In addition, due to the large
application amount of biogas slurry, one-time
application may cause leakage, resulting in the loss
of some biogas slurry nutrients. split fertilization can
reduce the application amount of single biogas
slurry.
When the proportion of biogas slurry instead of
chemical fertilizer was 70%, the root weight of
maize growed most vigorously (Fig. 2c). It can be
clearly observed that the root fine whiskers increase.
ICBEB 2022 - The International Conference on Biomedical Engineering and Bioinformatics
118

At this time, the root weight of split fertilization
treatment was 39.01% higher than that of one-time
fertilization. The plant height of maize reaches the
maximum when the proportion of biogas slurry
replacing chemical fertilizer was 60% (Fig. 2d), and
the maximum stem circumference and leaf number
reached the maximum when the proportion of biogas
slurry replacing chemical fertilizer was 70% (Fig.
2e, Fig. 2f). Under the best conditions, the effect of
one-time fertilization was better than that of split
fertilization. It can be found in combination with
several physiological character indexes of maize,
When the proportion of biogas slurry replacing
chemical fertilizer was high, the effect of one-time
fertilization is better than split fertilization. It is
similar to that of Xu et al. (Xu 2021), which explains
that biogas slurry partially replacing chemical
fertilizer can improve the biological yield and feed
quality of crops.
Figure 1.Effects of biogas slurry instead of chemical fertilizer on soil nutrients
0
0.3
0.6
0.9
1.2
1.5
20% 40% 60% 70% 80% 100%
Soil total phosphorus（g kg
-1
）
Proportion of biogas slurry replacing chemical fertilizer
Split fertilization
Single basal application
( a )
0
5
10
15
20
25
20% 40% 60% 70% 80% 100%
Soil available phosphorus（mg kg
-1
）
Proportion of biogas slurry replacing chemical fertilizer
Split fertilization
Single basal application
(
b
)
0
20
40
60
80
100
120
140
20% 40% 60% 70% 80% 100%
alkali hydrolyzable nitrogen（mg kg-1）
Proportion of biogas slurry replacing chemical fertilizer
Split fertilization
Single basal application
(c)
0
8
16
24
32
40
20% 40% 60% 70% 80% 100%
Soil nitrate nitrogen（mg kg
-1
）
Proportion of biogas slurry replacing chemical fertilizer
Split fertilization
Single basal application
(d)
0.0
0.3
0.6
0.9
1.2
1.5
1.8
20% 40% 60% 70% 80% 100%
Soil ammonium nitrogen（mg kg
-1
）
Proportion of biogas slurry replacing chemical fertilizer
Split fertilization
Single basal application
(e)
0.0
0.4
0.8
1.2
1.6
2.0
20% 40% 60% 70% 80% 100%
Soil total nitrogen（g kg
-1
）
Proportion of biogas slurry replacing chemical fertilizer
Split fertilization
Single basal application
(f)
0
300
600
900
1200
1500
20% 40% 60% 70% 80% 100%
Whole plant weight（g）
proportion of biogas slurry replacing chemical fertilizer
Split fertilization
Single basal application
(a)
0
300
600
900
1200
1500
20% 40% 60% 70% 80% 100%
Blade weight（g）
proportion of biogas slurry replacing chemical fertilizer
Split fertilization
Single basal application
(b)
Effects of Biogas Slurry Instead of Chemical Fertilizer on Soil Nutrients and Maize Growth
119

Figure 2: Effects of biogas slurry instead of chemical fertilizer on agronomic characters of maize.
4 CONCLUSION
The combined use of biogas slurry and chemical
fertilizer can increase the utilization efficiency of
nitrogen and phosphorus and increase the yield of
silage corn. The maximum values of corn weight per
plant and leaf weight were obtained in the range of
60% to 70% of biogas slurry instead of chemical
fertilizer, and the maximum values were 1064.37 g
and 959.13 g respectively. When the biogas slurry
instead of chemical fertilizer was 60% and 70%, the
silage corn yield of one-time fertilization was always
greater than split fertilization. When the ratio of
biogas slurry to chemical fertilizer is 80%, the
maximum content of total phosphorus in soil can
reach 725.31 mg kg
-1
. When the ratio of biogas
slurry to chemical fertilizer is 60% and 70%, the
content of rapid available phosphorus is large, up to
15.76 mg kg
-1
;the content of soil total nitrogen,
ammonium nitrogen and nitrate nitrogen was the
highest when the proportion of biogas slurry
replacing chemical fertilizer was 80%, while the
content of soil alkali hydrolyzable nitrogen was the
highest when the proportion of biogas slurry
replacing chemical fertilizer was 70%, and the
maximum values were 1.33 g kg
-1
, 1.50 mg kg
-1
,
33.99 mg kg
-1
and 127.27 mg kg
-1
, respectively. In
terms of the yield of silage corn and the content of
soil nutrients, and the effect is the best when the
proportion of biogas slurry instead of chemical
fertilizer was between 60% and 80%.
ACKNOWLEDGMENTS
This work was supported by Sichuan Province
Science and Technology Support Program
(2021YFN0125), Key Laboratory of Development
and Application of Rural Renewable Energy,
Ministry of Agriculture and Rural Affairs, China
(2020-002) and Mianyang Science and technology
project (2018YFZJ019).
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