Abstract

SAENGER, A., GEISSELER, D., LUDWIG, B. 

J. Plant Nutr. Soil Sci. 173,692-698 (2010)

Soil moisture affects the degradation of organic fertilizers in soils considerably, but less is known about the importance of rainfall pattern on the turnover of C and N. The objective of this study was to determine the effects of different rainfall patterns on C and N dynamics in soil amended with either biogas slurry (BS) or composted cattle manure (CM). Undisturbed soil cores without (control) or with BS or CM, which were incorporated at a rate of 100 kg N ha–1, were incubated for 140 d at 13.5°C. Irrigation treatments were (1) continuous irrigation (cont_irr; 3mm d–1); (2) partial drying and stronger irrigation (part_dry; no irrigation for 3 weeks, 1 week with 13.5mm d–1), and (3) periodic heavy rainfall (hvy_rain; 24mm d–1 every 3 weeks for 1 d and 2mm d–1 for the other days). The average irrigation was 3mm d–1 in each treatment. Cumulative emissions of CO2 and N2O from soils amended with BS were 92.8 g CO2-C m–2 and 162.4 mg N2O-N m–2, respectively, whereas emissions from soils amended with CM were 87.8 g CO2-C m–2 and only 38.9 mg N2O-N m–2. While both organic fertilizers significantly increased CO2 production compared to the control, N2O emissions were only significantly increased in the BS-amended soil. Under the conditions of the experiment, the rainfall pattern affected the temporal production of CO2 and N2O, but not the cumulative emissions. Cumulative NO-3 leaching was highest in the BS-amended soils (9.2 g NO-3 -N m–2) followed by the CM-amended soil (6.1 g NO-3 -N m–2) and lowest in the control (4.7 g NO-3 -N m–2). Nitrate leaching was also independent of the rainfall pattern. Our study shows that rainfall pattern may not affect CO2 and N2O emissions and NO-3 leaching markedly provided that the soil does not completely dry out.