Effect of fertilizer and water content on N_2O emission from three plantation soils in south China

Article type: Research Article

Authors: LI, Zhi-an | ZOU, Bi | XIA, Han-ping | DING, Yong-zhen | TAN, Wan-neng | MA, Zhen-rong

Affiliations: South China Botanical Garden, Chinese Academy of Sciences, Guangzhou 510650, China

Note: [] Corresponding author. E-mail: [email protected]

Abstract: The effects of fertilizers and water content on N_2O emission were studied using the three most typical plantation soils. Soil incubations were performed and fertilization and water content treatments were designed. At 25% of saturated water content (SWC), N_2O emissions from the soil treated with urea, KNO_3, (NH_4)_2 SO_4 and KH_2 PO_4 were compared at application rates of 0, 100, 200, 300 and 500 kg/hm^2. At 80% of SWC, similar experiments were carried out but at only one application rate (500 kg/hm^2). N_2O emissions at various water contents (20%, 35%, 50%, 65%, 80% and 100% of SWC) were studied. At low water content (25% of SWC), neither nitrogen nor phosphorus (or potassium) fertilizers led to a high level of N_2O emission, which generally ranged from 2.03 to 29.02μg/(m^2·h). However, at high water content (80% SWC), the fertilizers resulted in much greater N_2O emission irregardless of soil tested. The highest NO_2 emission rates after 24 h of water addition were 1233μg/(m^2·h) for S. superba soil, 1507μg/(m^2·h) for P. elliottii soil and 1869μg/(m^2·h) for A. mangium soil restively. N_2O emission from soils treated with urea, (NH_4)_2 SO_4 and KH_2PO_4 immediately dropped to a low level but steadily increased to a very high level for the soil treated with KNO_3. High NO_3^- content was a basis of high level of N_2O emission. N_2O emission rates from soils peaked shortly after flooding, rapidly dropping to a very low level in soil from non-legume plantations, but lasting for a relatively long period in soil from legume plantations. When soil water content increased equaling to or higher than 65%, the accumulated N_2O emission over a period of 13 d ranged from 20.21–29.78 mg/m^2 for S. superba, 30.57–70.12 mg/m^2 for P. elliottii and 300.89–430.51 mg/m^2 for A. mangium. The critical water content was 50% of SWC, above which a high level of N_2O emission could be expected, and below which very little N_2O emissions were detected. The results suggest that, at low water content (<50% of SWC), the fertilization practice is safe with regard to N2O emissions, but at high water content (>50% of SWC), nitrogen fertilizer in the form of nitrate could yield a 100-fold increase in N_2O emissions. Legume plantations like A. mangium should be avoided in low lands which could easily suffer from flooding or poor drainage.

Keywords: N[TeX:] _2O, plantation, south China, Acacia mangium, Pinus elliottii, Schima superba

Journal: Journal of Environmental Sciences, vol. 17, no. 6, pp. 970-976, 2005