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Environmental Impact Assessment of Surface Run-off to Small Stream in a Steep Cornfield

Joung-Du Shin, Jong-Sik Lee, Won-II Kim, Sang-Won Park1, Goo-Bok Jung, Yong-Sun Jhang and Dong-Sig Oh

*Department of Agricultural Environment and Ecology, Division of Agricultural Environment, National Institute of Agricultural Science and Technology, Rural Development Administration, Suwon 441-707, Korea
1
School of Plant Science, Seoul National University, Suwon 441-744, Korea

Abstract

This experiment was conducted to evaluate the nutrient loss and to assess the eutrophication into small stream by rainstorm in a steep cornfield during cultivation season. The crop cultivated was a silage corn (DW5969), and the experimental plots were divided into two parts that were 10 and 18% of slope degrees. The amount of Total-N and Total-P loss was calculated by analysis of surface run-off water quality, and investigated the effect of eutrophication to small stream as a part of life cycle assessment (LCA) methodology application. Total surface run-off ratio was not significantly different with slope degrees, but amount of T-N and T-P losses at 18% of slope degree were high as 5.96 kg/ha and 0.65 kg/ha as relative to 10% of slope degree, respectively. For the eutrophication to the small stream, it shown that PO4 equivalence and Eco-indicator value at 18% of slope degree were greater as much 6.11 kg/ha and 0.81 as compared to the slope angle 10%, respectively. Therefore, it was appeared that each effect of nutrient losses, eutrophication and Eco-indicator value was enhanced according with higher slope degree.

Media summary

For the environmental impact assessment of surface run-off on a steep cornfield in Korea, the effects of nutrient losses, eutrophication and Eco-indicator value were enhanced according with higher slope degree.

Keywords

Non-point source pollutants, equivalence factor and Eco-indicator 95 method

Introduction

Sustainable agricultural practices must be based on the appropriate management of water and soil. In areas with intensive rainfall, it tends to be non-point source pollutants that nitrogen, phosphorous and soil particles are conveyed into the water flowing system. These effluence rates are determined by rainfall and its intensity. In Korea, intense rainfall tends to occur in summer from June to early September. Yun et al. (2002) reported that NPS pollutants from agricultural practices are comprised only 5% of total pollutants entering into bulk water body. Kim et al. (1999) indicated that the concentrations of nitrogen and phosphorous in the drainage water was highest when fertilizer was applied during cropping season. NPS pollutants are mainly transported from steep cropland by surface run-off with rainfall, and responsible for the eutrophication. In order to examine the entire small stream burden connected with agricultural production systems, it is necessary to consider all non-point sources pollutants at the same time. Furthermore, the results show that LCA methodology is basically suitable to assess the environmental impact associated with agricultural production (Brentrup et al., 2001). It appeared that the LCA methodology is available tool to assess the environmental impact associated with different fertilizer applications for rice cultivation (Shin et al., 2003). Objectives of this study were to establish the potential attributed indicators with evaluating the nutrient loss and with assessing the eutrophication when run-off flowed into small stream by rainstorm in a steep cornfield during cultivation season.

Methods

The crop cultivated was a silage corn (DW5969), and the experimental plots were divided into two partial block areas that were 10 and 18% of slope degree by block. At the bases of sloped cornfield that directly connected into the small stream, two gauges were installed for measurement of run-off, and surface run-off samples collected every hour by auto-samplers for an analysis of water quality. The chemical characteristics of water were analyzed by standard methods (Korea EPA, 2000). For assessment of eutrophication to small stream, PO4 equivalence was calculated by modifying the Eco-indicator 95 method as follow:

Figures 1. Characterization of emissions for eutrophication in the Eco-indicator 95 method.

Also, Eco-indicator values was induced by following equation (Goedkoop, 1995): Eco-indicator value of eutrophication = ( Σn=i PO4 equiv./NV)*WF, where normalization value (NV) and weighing factor (WF) for eutrophication were 38.2 and 5, respectively.

Results

It appeared that the run-off ratios at 10 and 18% of slope degrees ranged from 12% to 43.2% and from 12.7% to 44.5%, respectively (Table 1). For the nutrient loss, the amount of T-N and T-P in the steep cornfield with 10% of slope degree were 21.74 kg/ha and 6.73 kg/ha, and were 27.70 and 7.38 kg/ha at 18% of slope degree, respectively (Table 2). Therefore, T-N and T-P losses at 18% of slope degree were high as 5.96kg/ha and 0.65kg/ha as compared to 10% of slope degree, respectively. In respective to the assessment of eutrophication in the steep cornfield, its loading amount based on PO4 equivalence is calculated with 35.6 and 41.72 kg/ha at each slope degrees (Fig. 2 and 3). Eco-indicator values in two steep cornfields with 10 and 18% of slope degrees were 4.66 and 5.47, respectively. So PO4 equivalence for eutrophication and Eco-indicator value at 18% of slope degree were greater at 6.11 kg/ha and 0.81 as compared to the slope degree 10%, respectively.

Table 1. Characteristics of run-off with different slope degrees in the steep cornfield during crop cultivation.

Parameters

Slopes 10%

Slope 18%

June

July

Aug.

June

July

Aug.

Rainfall (mm) (A)

126.0

422.0

170.0

126.0

422.0

170.0

Run-off (m3/ha) (B)

151.2

1321.0

734.6

160.1

1381.2

756.8

Run-off ratio (%) (B/A)

12.0

31.3

43.2

12.7

32.7

44.5

Table 2. Important of emissions (kg/ha) with different slope degrees in the steep cornfield during crop cultivation. (SS denotes suspended solids)

Slopes

Parameters

Cultivation periods

June

July

Aug.

Total

10%

SS (kg/ha)

2.00

20.58

19.93

42.51

T-N (kg/ha)

4.18

11.65

5.91

21.74

T-P (kg/ha)

0.07

4.27

2.39

6.73

NO3-N (kg/ha)

3.16

8.03

4.74

15.92

NH4-N (kg/ha)

0.05

0.64

0.19

0.88

18%

SS (kg/ha)

2.68

30.55

21.22

54.45

T-N (kg/ha)

4.18

17.42

6.11

27.70

T-P (kg/ha)

0.05

4.00

3.33

7.38

NO3-N (kg/ha)

3.00

13.97

4.59

21.56

NH4-N (kg/ha)

0.08

0.83

0.26

1.18

Figure 2. Effects of Eutrophication for run-off in the steep cornfield with different slope degrees during crop cultivation.

Figure 3. Eco-indicator values for environmental effect by run-off in the steep cornfield with different slope degrees during crop cultivation.

Conclusion

Total surface run-off ratios were not significantly difference between the slope degrees. For the nutrient loss in the steep cornfield, T-N and T-P losses at 18% of slope degree were high as 5.96 and 0.65 kg/ha as compared to 10% of slope degree, respectively. In assessment of eutrophication to small stream, PO4 equivalence and Eco-indicator value at 18% of slope degree were greater at 6.11 kg/ha and 0.81 as compared to the slope degree 10%, respectively. Overall, The nutrient losses, eutrophication and Eco-indicator value into the small stream were more affected by higher slope degree in the steep cornfield.

References

Brentrup, F., Kusters, J., Kuhlmann, J. and Lammel, J. (2001). Application of the life cycle assessment methodology to agricultural production: an example of sugar beet production with different forms of nitrogen fertilizers. European Journal of Agronomy 14, 221-233.

Goedkoop, M. (1995). NOH report 9523. the Eco-Indicator 95. Final Report. Pre Consultants, Amersfoort.

Kim, N.J., Oh, S.Y. and Kim, K.S. (1999). Characteristics and load of nitrogen and phosphorous in paddy field areas. Korean Soc. of Agricultural Engineering 44 (4), 47-50.

Korea Environmental Protection Agency (2000). Standard methods for the examination of water contamination (Ed.). pp. 141-347.

Shin, J.D., Lim, D.K., Kim, G.Y., Park, M.H., Koh, M.H. and Eom, K.C. (2003). Application the life cycle assessment methodology to rice cultivation in relation to fertilization. Korean Journal of Environmental Agriculture 22(1), 41-46.

Yun, S. G., Kim, W.I., Lee, J.S., Jung, G.B., Kim, J.H., Shin, J.D. and Koh, M.W. (2002). Assessment of agricultural non-point source pollutants and the management of agricultural soils. FFTC 552.

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