Crop Field Level Estimation of Nitrogen Input from Fertilizer Use in Jeju Island, South Korea: Management Methods to Prevent Groundwater NO3-N Contamination

Abstract

The application of synthetic nitrogen (N) fertilizers has boosted crop yields globally. However, it has also imposed on environmental pollution problems. An estimation of actual fertilizer N inputs at the crop field level is needed to establish effective N management plans to control groundwater NO3-N contamination. Here, a survey to collect the types of cultivated crop and fertilizer application rate was conducted during 2016–2018, covering 44,253 small crop fields (7730 ha) in the western part (Hanrim and Hankyung regions) of Jeju Island, South Korea. Foreign vegetables, citrus fruits, and bulb vegetables are the major crop types grown in the total cultivated areas of 2165.6 ha, 1718.7 ha, and 944.9 ha, respectively. For several crops (green garlic, potato, and chives), the over-use of N fertilizers is observed, the amount of which is 1.73–4.95 times greater than the standard fertilizer application rate. The highest level of fertilizer N input is observed for bulb vegetables in both the regions (Hanrim: 500.5 kg/ha, Hankyung: 487.1 kg/ha), with nearly 80% of the N fertilizer input turned into surplus N loading. A comparison between a spatial interpolation map of the fertilizer N input and that of the groundwater NO3-N concentration implies that the excessive use of synthetic fertilizer results in the degradation of groundwater quality by NO3-N. N management plans for the study area are suggested based on the N fertilizer input at the crop field level. This study highlights that sustainable N management plans should be arranged at the crop field level, considering the spatial heterogeneity of N fertilizer use.

Predicting Groundwater Indicator Concentration Based on Long Short-Term Memory Neural Network: A Case Study

“…Population growth, urbanization, and excessive extraction of groundwater lead to the water level declining severely [ 12 ]. Irrigation using groundwater also decreases the available quantity [ 13 ]. On the other hand, the quality of groundwater is worse and worse.…”

Groundwater nitrate pollution risk assessment based on the potential impact of land use, nitrogen balance, and vulnerability

“…Ortuzar-Iragorri et al ( 2018 ) calculated the gaseous and leached nitrogen balance. Koh et al ( 2021 ) estimated the nitrogen input from synthetic fertilizers by considering the nitrogen demand of crops. Kazakis et al ( 2015 ) performed groundwater pollution risk assessments by considering the risks from areal and local sources of pollution, using intrinsic groundwater vulnerability assessment methods dedicated to different types of aquifers.…”

Assessment of Ammonium–N and Nitrate–N Contamination of Shallow Groundwater in a Complex Agricultural Region, Central Western Taiwan

“…In comparison, nitrate is more easily leached into groundwater due to its high solubility and low soil adsorption capacity [3,8]. Because of its high potential risk to human health in drinking water [9][10][11][12], numerous surveys and analyses of soil nitrate leaching or nitrate contamination in groundwater caused by various agricultural activities have been widely reported e.g., [13][14][15][16][17][18][19][20]. Unlike nitrate, ammonium has very low toxicity to human health, and due to its low mobility in soil-water or aquifer systems [3,21], relatively few related studies have focused on evaluating ammonium contamination in aquifers from natural sources or anthropogenic activities [22][23][24][25][26].…”

“…A series of complex physical, chemical, and biochemical reactions in aeration layer and aquifer will jointly determine the main nitrogen pollution pattern of groundwater. Nitrogen loading from intense chemical fertilizer application to upland crops has been identified as a major source of high nitrate concentrations in groundwater [14,20,22,27,28]. On the contrary, regional investigation revealed that groundwater under flooded paddy fields is rarely polluted with nitrate [14,22], even though some studies have pointed out that nitrate is dominant in the leaching water of rice paddies [29,30] and paddy-wheat rotation systems [31][32][33][34].…”