Abstract
BACKGROUND: Estimation of soil nitrogen supply is essential to manage nitrogen fertilization in arable land. In Korea, nitrogen fertilization is recommended based on the soil organic matter content because it is difficult to assess nitrogen (N) mineralization of upland soils directly. In this study, the relationship between soil organic matter (SOM) content and N mineralization was investigated to explore the limitation of using SOM in predicting soil N mineralization. METHODS AND RESULTS: Soil samples from the 0 to 10 cm depth were collected from 18 individual pepper cultivated fields in Tae-an and Chung-yang provinces before fertilization. N mineralization in the soils was quantified using incubation for 70 days at $30^{\circ}C$. The mineralizable soil N (MSN) was positively correlated with SOM, and the relation equation between MSN and SOM was '$MSN(kg\;10a^{-1})=0.2933{\ast}SOM(g\;kg^{-1})+0.0897$ ($r^2=0.6224$, p<0.001)'. However, the differences of N mineralization among the soils with the similar concentrations of soil organic matter were about 3 to 4.6 times, suggesting that the other soil factors such as total N concentration or EC should affect N mineralization. CONCLUSION: We concluded that SOM alone could not reflect the capacity of soil to supply N that is used for recommendation of N fertilization rate. Therefore, other soil properties should be considered to improve N fertilization management in arable land for sustainable agriculture.
우리나라 노지 밭토양의 질소 비료 추천은 토양 유기물 범위에 따라 차등하여 추천한다. 토양 유기물 함량에 따른 질소 공급 가능량을 확인하기 위하여 노지 고추 재배 밭토양에서 작물 재배 전 토양을 채취하여 70일간 누적 질소 무기화량을 구하였다. 토양 유기물 함량(SOM)과 무기화 될 수 있는 토양 질소(SNM)의 관계식은 '$MSN(kg\;10a^{-1})=0.2933{\ast}SOM(g\;kg^{-1})+0.0897$ ($r^2=0.6224$, P<0.001)'이었다. 토양 유기물 범위별 평균 질소 무기화량은 각각 10.5, 26.6, 83.3, 105.6 mg kg-1으로 토양 유기물 함량이 많을수록 질소 무기화량도 많았으나, 같은 토양 유기물 범위에 속하는 토양이어도 질소 무기화량은 약 3~4.6배 차이가 있었다. 따라서 밭토양 질소 관리를 위해서는 토양 특성에 따른 질소 공급량 예측을 통해 질소 비료를 추천하는 것이 중요하다.
