IJERD – International Journal of Environmental and Rural Development (2013) 4-2

Research articleerd

The Nitrogen Runoff Characteristics in Agricultural
Watersheds after Enforcementof Animal Waste Regulation
I7den
TOSHIMI MUNEOKA*t
Obihiro University of Agriculture and Veterinary
Medicine, Hokkaido, Japan

Email: muneoka@obihiro.ac.jp

4.
YURI YAMAZAKI
7
Obihiro University of Agriculture and Veterinary
Medicine, Hokkaido, Japan
2

SACHIYO WAKOU

wo Fishery, Ibaraki Prefectural Government, Ibaraki,
Department of Agriculture, Forestry &rJapan

MOTOKO SHIMURAds

National Agriculture and Food Research Organization, Western Region Agricultural ResearchCenter, Farming Systems and Agro-Environmental Technologies Research Division,Hiroshima, JapanKUNIHIKO YOSHINO
Faculty of Engineering, Information and Systems Division of Policy and Planning Sciences,
University of Tsukuba, Ibaraki, JapanOSAMU TSUJI
Obihiro University of Agriculture and Veterinary Medicine, Hokkaido, JapanTOSHIO TABUCHI
Former professor of the University of Tokyo, Tokyo, Japan
Received 15 December 2012

Accepted 6 May 2013(*Corresponding Author)

Abstract In this study, the characteristics of nitrogen in river water at the normal waterlevel were examined for a period after the enforcement of animal waste regulation. The
differences in agricultural land use in the two study sites in Eastern Hokkaido were taken
into consideration. In 35 watersheds in the two areas, the total nitrogen (T-N), nitrate
nitrogen (NO3-N), nitrite nitrogen (NO2-N) and ammonium nitrogen (NH4-N)
concentrations, and the river discharges were investigated. A total of 7 investigations werecarried out during the period from late May to late November 2005. In the Tokachi area
(24 watersheds), the main land uses are upland and dairy farming. In the Nemuro area (11watersheds), the main land use is large-scale dairy farming. Irrespective of the land use in
the watershed, when the proportion of the agricultural land was about 20% or lower, thevalue obtained by adding the standard deviation to the annual mean T-N concentration ofriver water in many investigated watersheds was 1.0 mg/L or lower. When watersheds
whose proportion in the agricultural land was 65% or higher were examined, there weresome whose values obtained by adding the standard deviation to the annual mean T-Nconcentration were close to 10 mg/L. Decreasing trends were not identified in the nitrogenconcentration in river water investigated in the first year after enforcement of animal wasteregulation. From the viewpoint of water quality conservation, it is effective toappropriately adjust the use of chemical fertilizers in the cropland in the watersheds and toencourage dairy farmers to practice appropriate management of livestock manure.
Keywords nitrogen runoff, agricultural land use, animal waste regulation, water quality
conservation© ISERD56

IJERD – International Journal of Environmental and Rural Development (2013) 4-2

INTRODUCTION
Japan is in the Asian monsoons region. In Eastern Hokkaido, where large-scale farming has been
conducted under harsh climatic conditions, nitrate pollution of the local water system has been
pointed out. The concentration of nitrate nitrogen in river water and the extent of agricultural land
use in an investigated area were reported to have a positive correlation (Tabuchi et al., 1995; Woliet al., 2002; Woli et al., 2004; Muneoka et al., 2012).
Tabuchi et al. (1995) investigated the nitrate nitrogen concentration in river water and theagricultural land use in each area in Eastern Hokkaido in the summer of 1992. Yamazaki et al.
(2013) conducted a long-term observation on the relationship between nitrate nitrogenconcentration in river water and agricultural land use in the Tokachi and Nemuro areas based on
the observation results of Tabuchi et al. (1995). Their observation revealed that in some of thewatersheds where the nitrate nitrogen decreased in the summer of 2004 relative to the summers ofprevious years, the nitrate nitrogen actually increased significantly in 2005, and the increasing
trends continued in successive years. On the contrary, there have been few studies that observed theseasonal fluctuation of the river water quality in agricultural watersheds immediately before andafter the enforcement of animal waste regulation (Kato et al, 2006).
The present study examines the characteristics of nitrogen that flowed into river water at thenormal water level in two areas in Eastern Hokkaido in the first year after the enforcement ofanimal waste regulation. The study focuses on the differences in agricultural land use between thetwo areas.
METHODOLOGY
The maps of study sites are shown in Fig.1. The Tokachi area, which has 24 watersheds on theTokachi River system and the Shikaribetsu River system (No. 1 to 24), is located in theSampling
River name
PointN

Bridge nameArea
Land use ( %)(km2 ) Agricultural land Forest

Tokachi area

Hokkaido

Nemuro Area

Tokachi Area
Shibetsu River

Tokotan River

12
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24

TokachiOojika632
PenkenaiPennai23
Penkenikorbetsu Penkenikorobetsu
48
Penkenikoro
Minamiiwamatsu
72
TokachiNakajima1798
Shikaribetsu
Urimaku
217
Sikanosawa
Kikuchi5Kamihoronai
Kamihoronai
3
Shikaribetsu
Momiji256
Minami1sen
Nakashikakann2gou 13
Iketo
Minamisawa
9
Pankebibaushi Kousui
27
Urimaku( no bridge )9Poronai( no bridge )3
Urimaku
Mutsu
49
Penkeutorei
Honnmaki
3
Pankeutorei( no name )5Pankeutorei
Komadome
17
Penkechin
Okuyama26
Ponchin
Kamimaki
13
Penkechin
Isami
63
Pankechin
Sinnei10
PankechinTaneuma
72
Shikaribetu
Kunimi
667

102221
48388
1372
9590
1390
58889365
2275
4652
72489498
96
97
70
91
131281
172
766
732
11625
49
1833
32
1545

4732
3
22
32
49
81
1054
73

71
81
57
91
72
64
46
1460
32
21

Nemuro area

Shikaribesu RiverTokachi River

Nishibetsu River
Agricultural land
ForestOtherRiver
Sampling point

AB
C
D
E
FG
H
I
JK

Kanjiushi
KenekaKenekaShibetsu
Shibetsu
Masu
Masu
TokotanNishibetsu
Nishibetsu
Pononnebetsu

Yourouushi
MinoriHakuyou
Nagori
Kamisibetu
Masukawa
Kenebetsu
Houtoku
Kousai
Nishisyunnbetsu
AkashiFig. 1 Outline of the Tokachi and Nemuro areas© ISERD
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IJERD – International Journal of Environmental and Rural Development (2013) 4-2

northwestern part of the Tokachi General Sub prefectural Bureau, and it is an area with upland anddairy farming. The Nemuro area, which has 11 watersheds on the Shibetsu River system, theTokotan River system and the Nishibetsu River system (A to K), is located in the western part ofthe Nemuro Sub prefectural Bureau, and it is an area mainly of dairy farming. In both of these areas,large-scale farming has been operated, and there have been no considerable changes in agriculturalland use in either area since 1985.
In year 1981 to 2010, the annual mean air temperature and the yearly precipitation were 5.9℃
and 840.7 mm at Komaba in the Tokachi area, and 5.4℃ and 1158.0 mm at Nakashibetsu in thevicinity of the Nemuro area. Both areas have a relatively cold climate with less rainfall.
The investigation of the river water quality was conducted at the normal water level at 35
sampling points. Electric conductivity (EC) and water temperature were measured at sampling
points. Discharge was also measured on the rivers in small watersheds (21 to 24 samples permonth). Analysis for some water quality components were done after the field investigation. The
total nitrogen (T-N), nitrate nitrogen (NO3-N), nitrite nitrogen (NO2-N) and ammonium nitrogen(NH4-N) concentrations were used as indices in this study. The 7 investigations were carried out
during the period from late May to late November 2005.
The GIS software application ArcGIS Desktop (Ver. 10, ESRI) was used for analyzing land
use in the study sites. The data were “rivers”, ”watershed boundaries” and “detailed land use mesh”
from digital national information to determine the proportion of agricultural land in watersheds.
The detailed land use mesh (100 m × 100 m) shows 11 types of land uses; however, we redefined
the mesh into the three items of “agricultural land”, “forest” and “other”. The proportion ofagricultural land was determined for each watershed by overlaying the watershed map created forthe sampling points on the detailed land use mesh.
RESULTS AND DISCUSSION
In Japan, there are two major water quality standards that use nitrogen as indices. “TheEnvironmental Standards Concerning the Protection of Human Health” specifies the highest
acceptable combined concentration of NO3-N and NO2-N as 10 mg/L. Some standards with “TheEnvironmental Standards Concerning the Conservation of the Living Environment” specify thehighest acceptable concentration of T-N as 1.0 mg/L.
For an examination of the characteristics of the seasonal fluctuations in nitrogen concentrationof river water at 35 sampling points in the two investigated areas in 2005, the annual mean nitrogenconcentration and the standard deviation are shown in Fig.2 (a), (b).
The T-N concentration in river water in the two areas was compared using the coefficient ofvariation (standard deviation divided by the mean). The values for the Tokachi area (24 samplingpoints) were 12% to 77% and those for the Nemuro area (11 sampling points) were 7% to 27%.
The range of seasonal fluctuation of T-N concentration in river water was smaller in the Nemuroarea than in the Tokachi area.
Among the all sampling points, the number of sampling points where the sum of annual mean
T-N concentration and the standard deviation were 1.0 mg/L or lower was 7 points in the Tokachiarea and 6 points in the Nemuro area. The proportion of agricultural land in the watersheds in theseareas were <1 - 22% in the Tokachi area and 3 - 32% in the Nemuro area. It was found thatirrespective of the land use differences, if the proportion of agricultural land was 20% or lower, thenitrogen concentration in the river water in many watersheds was 1.0 mg/L or lower.
Differences were clearly found in the characteristics of the fluctuations in nitrogen concentration
between the two areas when the value of T-N concentration in the watersheds exceeded about 3.0
mg/L. There were some sampling points in the Tokachi area whose values for T-N concentrationand standard deviation combined were close to the 10 mg/L, specified in “The EnvironmentalStandards Concerning the Protection of Human Health”. At 5 sampling points (No.11, 14, 16, 18and 20) among the above 14 points, the coefficient of variation was 30% or greater. These fivewatersheds had features that are in common, such as small areas of 3 - 17 km2 and a highproportion of agricultural land of 65% - 95%. In the Nemuro area, however, only one watershed© ISERD
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IJERD – International Journal of Environmental and Rural Development (2013) 4-2

had the T-N concentration and standard deviation combined that exceeded about 3.0mg/L. For thiswatershed, the coefficient of variation was 13%, which was relatively small, the area was 23 km2,
and the proportion of agricultural land was 81%.
(b) Nemuro area

Sampling point(a) Tokachi area
12
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
2324

Sampling point1)
2)

Standard deviation of T-NABCDEFGHIJK1)
2)Standard deviation of T-N

0.0

1.0

NO3-N

2.0
3.0
T-N (mg/L)

NO2-N

NH4-N

4.0

5.0

Org.-N** organic nitrogen

1) Some standards of T-N (≦1.0 mg/L)
2) T-N = 3.0 mg/L line
0.0

2.0

4.0
6.0
T-N (mg/L)

8.0

10.0

Fig. 2 The annual mean nitrogen concentration and the standard deviationof the river water in the watersheds in the Tokachi and Nemuro areas
Fig.3 shows the regression lines and the calculated coefficients of correlation, which indicate
the relationship between the NO3-N concentration in river water and the proportion of agriculturalland in the watersheds. The NO3-N was used as the index on this study, because T-N in the riverwater mainly consisted of NO3-N in general.
The relationship between the NO3-N concentration in river water (Y) and the proportion ofagricultural land in the watershed (X) is expressed as Y = a X. The slope “a”, which indicates theimpact factor (IF) value, for the both areas in 2005 were 0.026 - 0.054 in the Tokachi area and0.020 - 0.029 in the Nemuro area. When two watersheds, one from the Tokachi area and the otherfrom Nemuro area, that had similar proportion of agricultural land were compared, the NO3-N
concentration in the river water at the similar investigation period tended to be higher in theTokachi area. The IF in the Tokachi area showed particularly high values that exceeded 0.050 fromJuly to September.
When the coefficient of correlation r for both areas was examined by using the NO3-N
concentration as the index, r for the Tokachi area were 0.67※※ - 0.89※※, and that for the Nemuroarea were 0.94※※ - 0.96※※. These coefficients are all positive and significant at the 1 percent level.
The correlation was constantly higher in the Nemuro area throughout 2005.
As discussed above, comparison between the annual mean nitrogen concentrations in riverwater in the two areas in the first year after the enforcement of animal waste regulation (2005)
showed that the nitrogen concentration was relatively low and stable in the Nemuro area, while it
was high and varied greatly in the Tokachi area.
In the Nemuro area, agricultural land use had been unified into grassland, and the major
loading source of water contamination derives from livestock manure. Therefore, it can be assumed
that the seasonal variation in the nitrogen concentration of the river water was relatively small andhad a high correlation with the proportion of agricultural land in the watershed.

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IJERD – International Journal of Environmental and Rural Development (2013) 4-2

NO3-N (mg/L)

8.0

NO3-N (mg/L) [ Y = a X ]◎2005.7
Investigated
month

6.0
Y = 0.054 X
r = 0.87 ※※

4.0

2.0
Y = 0.023 X
r = 0.94 ※※0.0020406080100

Tokachi area
a*r

Nemuro area
a*r

N.B

2005.50.028

0.69 ※※

0.020

0.95 ※※

2005.60.026

0.67 ※※

0.020

0.95 ※※

2005.70.054

0.87 ※※

0.023

0.94 ※※ ◎2005.8

0.051

0.89

※※

0.024

0.95 ※※

2005.90.052

0.84 ※※

0.028

0.96 ※※

2005.100.041

0.73 ※※

0.025

0.95 ※※

2005.110.042

0.76 ※※

0.029

0.96 ※※

Proportion of agricultural land (%)
Tokachi area

Nemuro area

* The impact factor (IF)※※ significance of 1%

Fig. 3 Relationship between the NO3-N of the river water and the proportionof agricultural land in watersheds in the Tokachi and Nemuro areas
In the Tokachi area, land use was for dairy farming and the farming of various upland crops.
In addition to livestock manure, the loading source includes chemical fertilizers that were appliedin large quantities to the upland fields. It is assumed that the use of chemical fertilizers contributed
to the higher concentration of nitrogen in river water and that the larger range of seasonal variationin the nitrogen, concentration was attributable to the use of chemical fertilizers during the peakseason of agricultural farming.
CONCLUSION
By focusing on the difference in agricultural land use in the watersheds of two areas in Eastern
Hokkaido, the nitrogen outflow characteristics were examined for river water at the normal waterlevel at 35 sampling points in the two areas. The examinations found that, in the first year after theenforcement of animal waste regulation (2005), the nitrogen concentration in river water in the twoareas showed different behavior depending on the differences in agricultural land use. In theTokachi area, the nitrogen concentration in river water tended to be high in many watersheds. In
small watersheds with a high proportion of agricultural land, the nitrogen concentration in riverwater during the summer period (July to September) showed great increases. To conserve the water
environment by decreasing the concentration of nitrogen in river water, it is necessary to control
nitrogen loading during the summer seasons not only by promoting appropriate use of chemicalfertilizers in croplands but also by encouraging individual farmers to practice appropriate
management of livestock manure.
ACKNOWLEDGEMENTS
The authors are grateful for the research assistance provided by the students in Obihiro Universityof Agriculture and Veterinary Medicine.
REFERENCES
Kato, T., Ishijima, T., Kuroda, H., Nakasone, H. and Kiri, H. 2006. Runoff characteristics of nutrients before
and after enforcement of animal waste regulation. J. Jpn. Soc. Water Environ., 29, 687-692 (in Japanesewith English abstract).
Muneoka, T., Okazawa, H., Tsuji, O. and Kimura, M. 2012. The nitrate nitrogen concentration in river waterand the proportion of cropland in the Tokachi River watershed. IJERD, 3-2, 193-199.

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Tabuchi, T., Yoshino, K., Shimura, M., Kuroda, S., Ishikawa, M. and Yamaji, E. 1995. Relation between
land use and nitrate concentration of outflow water from watersheds of agricultural and forest area, Japan.
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