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ISSN : 1225-8504(Print)
ISSN : 2287-8165(Online)
Journal of the Korean Society of International Agricultue Vol.29 No.3 pp.323-328
DOI : https://doi.org/10.12719/KSIA.2017.29.3.323

Characteristics of Inorganic Nitrogen and Phosphorus Runoff under Different Water Management Treatments in Irrigated Paddy Fields

Kyeong-Bo Lee*, Gyeong-Dan Yu*, Kyung-Do Lee**, Chan-Won Park**, Deog-Bae Lee**
*Bioenergy Crop Research Institute, National Institute of Crop Science, RDA, Muan, 58545, Republic of Korea
**National Institute of Agricultural Sciences, RDA, Wanju, 55365, Republic of Korea
Corresponding author : +82-61-450-0195lee1214@korea.kr
July 19, 2017 August 31, 2017 September 20, 2017

Abstract

The objective of this study was to quantify and characterize the inorganic nitrogen and phosphorus outflow loading from different water managements in paddy fields. We investigated the NO3-N, NH4-N, and PO4 in runoff from paddy fields in Iksan. The three different water management treatments were conventional continuous irrigation at 4 and 8 cm water levels, and intermittent irrigation at a 4 cm water level. The concentration of NO3-N at the early growth stage in surface water was 6.11 mg L-1, and then it gradually decreased. The downward curve increased slightly with additional nitrogen fertilization at the panicle initiation stage, and then it continued to decrease. The NH4-N concentration was 5.26 mg L-1, and that of PO4 was 0.70 mg L-1 at the early growth stage. However, the concentration of NO3-N peaked at 8.79 mg L-1 directly after transplantation and then decreased rapidly throughout the growing season. The amount of NH4-N runoff was 1.86 kg ha-1 in the plot with intermittent irrigation, and 2.0 kg ha-1 and 2.1 kg ha-1 in the plots with water depths of 4 and 8 cm, respectively. The NO3-N runoff was 7.43 kg ha-1 in the plot with intermittent irrigation, 8.62 kg ha-1 in the plot with a water depth of 4 cm, and 10.25 kg ha-1 in the plot with a water depth of 8 cm. In addition, the PO4 runoff was 0.42 kg ha-1 in the plot with intermittent irrigation, 0.48 and 0.55 kg ha-1 in the plots with water depths of 4 and 8 cm, respectively. The saving effect of irrigation water was 28.5% than that of conventional water management treatments, and the amount of nitrogen runoff was decreased by 18.5% with intermittent irrigation. However, the phosphorus runoff was not different between the different water management treatments in paddy fields.


논 토양에서 논물 담수심에 따른 무기태 질소, 인의 유출 특성

이 경보*, 유 경단*, 이 경도**, 박 찬원**, 이 덕배**
*농촌진흥청 국립식량과학원 바이오에너지작물연구소
**농촌진흥청 국립농업과학원

초록


    Rural Development Administration
    PJ00107101

    Introduction

    The need to reduce nitrogen (N) and phosphorus (P) runoff into aquatic ecosystems to resolve fresh water and eutrophication problems has been widely recognized (Conley et al., 2009). N and P usually enter aquatic ecosystems in surface discharge from nonpoint sources such as sewage effluent, agricultural drainage, and pasture watershed areas (Lee et al., 2005). Water pollution by nonpoint sources are more difficult to control than point source pollution owing to difficulties in identification and runoff characteristics. The contribution rate of nonpoint source pollution reached to about 75% in watersheds in Korea, and the contribution from agricultural nonpoint sources has been increasing (Rural Research Institute, 2002).

    Agricultural areas that contribute 57% of the total N and P loads of nonpoint source pollution are the main source of nutrients in agricultural water sheds, since they have high fertilizer loads than natural ecosystems, such as forests (5.5%)(Ministry of Environment, 1995). These percentages seem to underestimate the total nitrogen and phosphorus losses from agriculture because they do not include percolation and seepage, which ultimately carry N and P to water bodies. In Korea, paddy fields occupy about 60% of the agricultural land and have a close relationship with water pollution in streams and lakes owing to their connectivity to these watersheds. In addition, paddy field irrigation is distinguished by alternative irrigation and drainage practices, and large amounts of irrigation water use (Kim et al., 2006). The runoff of the major fertilizers N and P, from paddy fields differs with the fertilization rate, fertilization time, and method of nutrient application, the amount and timing of irrigation and rainfall, and storm events (Chapagain and Yamaji, 2010; Kim et al., 2006). N and P fluxes increased after the application of fertilizers to farm land, and higher N and P application rates (Sharpley and Rekolainen, 1996). Runoff loading of N and P with rainfall intensity was different in different paddy fields (Cho et al,, 1999; Yang, 2006).

    Transportation of N and P to surface water by runoff could be reduced by intermittent irrigation methods in paddy culture. Conventional standing water irrigation methods incorporated with drainage during the rice season could be used to control non-productive tillers soil conditions. Unlike previous methods, intermittent irrigation is focused on maintaining field moisture conditions by irrigation after the disappearance of applied ponded water. This irrigation method could save 25-50% of water with insignificant loss of yield and dry matter than that of standing water irrigation (Peng et al., 1994).

    The present study was conducted to clarify the effects of irrigation regimes on runoff of N and P, and water consumption in paddy fields of rice cultivation areas in Korea.

    Materials and Methods

    We carried out this study using three treatments, including standing irrigation at water depths of level 8 and 4 cm, and intermittent irrigation at 4 cm. Each, treatment was replicated three times using a randomized complete block design in the fluvio-marine paddy soil of the Honam plain. Table 1 shows the physico-chemical properties of the soil used. The soil texture was silt loam, containing 9.4% sand, 74.8% silt, and 16% clay. The concentrations of soil organic matter and available phosphate were 29.2 g kg-1 and 110 mg kg-1, respectively.

    The rice cultivar, Dongjin1ho, was transplanted on May 28 for two years. The planting distance was 15 × 30 cm. The amount of chemical fertilizers was N : P2O5 : K2O = 110 : 45 : 57 kg ha-1. Urea (N 46%) was applied as a N fertilizer, calcium superphosphate (P2O5 12%) as a P fertilizer, and potassium chloride (K2O 60%) as a potassium (K) fertilizer. During the rice cultivation, to evaluate the emission of N and P, we analyzed the concentrations of inorganic N and P in irrigation and runoff water. The water infiltrated through the soil was collected with a Porous cup buried in soil at a depth of 60 cm with three replications. Surface water in paddy field was sampled 3, 5, 7, and 10 day after transplanting. Thereafter, the sample was taken at a regular interval of seven days and the inorganic N and P, was analyzed using with Colorimetric methods (MOE, 1999; MOE, 2000; AOAC, 1980).

    Results

    Table 2 shows the irrigation and runoff of surface water in paddy fields with different treatments during rice cultivation in the first year. Rainfall during rice cultivation was 992 mm. Irrigation in the treatment blocks with a water depth of 8 cm was 550 mm, and 440 mm with a water depth 4 cm, and 355 mm with intermittent irrigation. The runoff in the treatment blocks with intermittent irrigation was 401 mm, which was the lowest among the treatments.

    Table 3 shows the amount of irrigation and runoff of surface water in paddy fields with different treatments during rice cultivation in the second year. Rainfall during rice cultivation was 994 mm. Irrigation in the treatment blocks with a water depth of 8 cm was 477 mm, and 409 mm with a water depth of 4 cm, and 310 mm with intermittent irrigation. The amount of irrigated water for the intermittent irrigation decreased by 35% and 25% than that of the irrigated water at depths 8 and 4 cm, respectively. The monthly runoff was considerable in July owing to heavy rainfall than that of the other months.

    Fig. 1 shows the change of the concentration of NO3-N, NH4-N, and PO4 in surface water. The concentration of NO3-N at the early growth stage in surface water was 6.11 mg L-1, which then gradually decreased. After N fertilization at the panicle initiation stage, it increased again. The concentration of NH4-N was 5.26 mg L-1, and that of PO4 was 0.70 mg L-1 at the early growth stage.

    Inorganic N dynamics during rice cultivation could be affected by many factors, such as fertilization, soil N, N loss, denitrification, volatilization, N fixation, and rice N uptake. NH4-N dynamics started to increase after 20 d from transplantation.

    The results of the analyses of the concentration of each component in the soil solution at a soil depth of 60 cm to investigate the leaching behavior of NO3-N, NH4-N, PO4 are shown in Fig. 2. The concentration of NH4-N, PO4 in the soil solution was < 0.5mg L-1, indicating a small change of their concentrations. However, the NO3-N concentration was the highest shortly after transplantation at 8.79 mg L-1. and then, it rapidly decreased. As a result, the change of N dynamics was as follows: organic-N → NH4- N → NO2-N → NO3-N (Lee et al., 1997). At the end of the cycle, NO3-N could be taken up by crop; however, it was mostly accumulated in the subsoil layer, playing a role as a pollutant by leaching because the adsorptive capacity by soil was weak and the mobility was high.

    The amount of the runoff with nutrient loading is different depending on precipitation, physicochemical properties of soil, the amount of fertilizer used and fertilization method, and water management regime. During the rainfall in the rice-growing season, inorganic N and P were examined to evaluate the characteristics of runoff according to water management treatments.

    Fig. 3 shows the pattern of runoff of inorganic N and P according to ponded water depth in 2004. Runoff of NO3- N was highest at a treatment of 8 cm water depth, and it peaked at 3.19 kg ha-1 26 d after transplantation. High concentrations during the early growing period may be the result of the high concentration of N in ponded water and heavy rain.

    Yoon et al. (2002) reported that N and P concentration in runoff were different with different rainfall patterns, but generally increased with increased precipitation

    The NO3-N concentration in runoff decreased < 1 kg ha-1 from 30 d after transplantation. PO4 in the runoff was very low than that of NH4-N NO3-N, because it is difficult to dissolve in water and become fixed in soil, so is less affected by water flow. The runoff characteristics of N and P in 4- cm water depths were similar to that of 8- cm depth, but the amounts were lower. In intermittent irrigation, the runoff of N and P was lower than both treatments of the ponded water depths. The amount of water runoff was insignificant in results of increased soil capacity by lowered water potential in intermittent irrigation plot.

    Fig. 4 shows the runoff pattern of inorganic N and P according to irrigated water depth in 2005. Runoff of NO3- N was largest at 3.05 kg ha-1 in 37 d after transplantation. It was decreased since the peak and reached 1.16 kg ha-1 67 d after transplanting. Runoff characteristics of inorganic N and P showed a similar pattern between the treatments, but the amounts were different from each other. Yoon et al. (2003) reported that the N and P outflow loading from paddies is affected by the water regime, and pollutants loading from paddy can be diminished by reducing the runoff during fertilization periods.

    Table 4 illustrates the amounts of N and P runoff during rice cultivation in 2004 and 2005. In 2004, the runoff of NH4-N was 2.4 kg ha-1 in plot with intermittent irrigation, 2.32 kg ha-1 and 2.19 kg ha-1 in the plots with water depths 8 and 4 cm, respectively. The runoff of NO3-N was 7.34 kg ha-1 in the plot with intermittent irrigation, whereas it was 11.53 kg ha-1 in the plot with a water depth of 8 cm, and 8.64 kg ha-1 in the plot with a water depth of 4 cm.

    The runoff of PO4 was 0.30 kg ha-1 in the plot with intermittent irrigation, 0.46 kg ha-1 and 0.34 kg ha-1 in the plots with water depths of 8 and 4 cm, respectively. In 2005, the runoff of NO3-N was 7.50 kg ha-1 in the plot with intermittent irrigation, whereas it was 8.96 kg ha-1 in the plot with a water depth of 8 cm, and 8.59 kg ha-1 in the plot with a water depth 4 cm. However, the runoffs of P by treatments were not different between the different water management treatments in paddy fields.

    Kim & Cho (1995) reported that N and P runoff during rice cultivation using rice paddy drainage from a Korean paddy field in Hwaseong-gun County was 15 and 0.59 kg ha-1, respectively. Cho et al. (1999) also reported that runoff of N and P was 12.37 and 2.16 kg ha-1, respectively, from a paddy field in the same county. Nutrient runoff from paddy fields could be changed by cultivation practices and environmental factors based on these results of paddy fields located in close to each other. Therefore, it is important to reduce the nutrient loading by adapting improved water management in the early days of planting, and focusing more on runoff than subsurface flow.

    Conclusions

    Although several studies have been conducted to improve the efficiency of nutrients in paddy fields to dater, there are many factors are involved in nutrient runoff; therefor, more comprehensive research is necessary. A study concerning a change of agricultural environment is needed. In addition, technology for the reduction of environmental pollutant loading and knowledge on nutrient behavior are required for sustainable agriculture. Our study shows that irrigation management is an important factor for reducing nutrient loading and conserving water for rice cultivation. The conservation of irrigation water during intermittent irrigation was 28.5% that of conventional water management treatments. The amount of N runoff was decreased 18.5% by the intermittent water management treatment. However, the P runoff was not different between the different water management methods in paddy fields. The results of the present study indicate that the N and P runoff could be reduced by intermittent irrigation methods in paddy fields.

    적 요

    논으로부터 비점오염 저감을 위해 벼 재배기간 동안 담수 깊이에 따른 질소, 인 유출을 평가한 결과는 다음과 같다.

    • 1. 담수 8 cm 처리구의 관개량은 514 mm, 담수 4 cm 처 리구의 관개량은 425 mm, 최대용수량 처리구의 관개량은 333 mm 이었으며, 유출량은 간단관개 처리구에서 408 mm로 가장 적었다.

    • 2. 재배기간 중 표층수 중 NO3-N 농도는 벼 생육초기 6.11 mg L-1이었으며, NH4-N 농도는 5.26 mg L-1이었고, PO4 농 도는 0.70 mg L-1이었다.

    • 3. 60 cm 토양용액 중 NH4-N와 PO4 농도는 벼 전 생육기 간 동안 0.50 mg L-1이하였으며, 농도 변화는 크지 않았다. NO3-N 농도변화는 벼 이앙 초 8.79 mg L-1로 가장 높았으며, 그 이후 급격히 감소하였다.

    • 4. 벼 생육기간 동안 NH4-N 유출량은 간단관개구가 1.8 6 kg ha-1, 담수 4cm와 8cm 처리구가 2.0 kg ha-1, 2.1 kg ha-1 이었다. NO3-N 유출량은 간단관개구가 7.43 kg ha-1, 담수 4 cm 처리구는 8.62 kg ha-1, 담수 8cm 처리구는 10.25 kg ha-1이었다.

    • 5. PO4 유출량은 간단관개구가 0.42 kg ha-1, 담수 4 cm 와 8 cm 처리구가 각각 0.48 kg ha-1, 0.55 kg ha-1이었다. 질소 유 출량은 담수심을 낮게 함으로서 18.5% 의 질소유출을 줄일 수 있었으며, 인의 유출량은 처리별 차이가 없었다.

    ACKNOWLEDGMENTS

    This work was carried out with the support of “Cooperative Research Program for Agriculture Science & Technology Development (Project No. PJ 00107101)” Rural Development Administration, Republic of Korea.

    Figure

    KSIA-29-323_F1.gif

    The change of NO3-N, NH4-N, and PO4 concentrations in the surface water

    KSIA-29-323_F2.gif

    The change of NO3-N, NH4-N and PO4 concentration in soil solutions at a 60 cm soil depth

    KSIA-29-323_F3.gif

    Runoff of NO3-N, NH4-N, and PO4 during rice cultivation under different water management treatments in the first year (top : water depth 8 cm, middle : water depth 4 cm, bottom : intermittent)

    KSIA-29-323_F4.gif

    Runoff of NO3-N, NH4-N, and PO4 during rice cultivation under different water management treatments in the second year (top : water depth 8 cm, middle : water depth 4 cm, bottom : intermittent irrigation)

    Table

    Physico-chemical properties of the soil used.

    The amount of irrigation and runoff for the different treatments in the first year (Unit : mm)

    The amount of irrigation and runoff for the different treatments in the second year (Unit : mm)

    The amount of nitrogen and phosphorus runoff for different water management treatments during rice growth (Unit : kg ha-1)

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