The changes of soil mineral nitrogen observed on farms between autumn and spring and modelled with a simple leaching equation
J. Haberle, H. Kusá, P. Svoboda, J. Klírhttps://doi.org/10.17221/7/2009-SWRCitation:Haberle J., Kusá H., Svoboda P., Klír J. (2009): The changes of soil mineral nitrogen observed on farms between autumn and spring and modelled with a simple leaching equation. Soil & Water Res., 4: 159-167.
The content of nitrate or mineral nitrogen (Nmin = N-NO-3 + N-NH +4) in soil in autumn is recognized as the indicator of potential risk of N leaching during winter. In this contribution, the apparent changes of Nmin in the 0–60 cm soil layer, during winter, on farm fields in the Czech Republic were calculated. A significant positive relationship between Nmin in autumn and the change during winter was observed in eight out of the nine farms. Nitrate N data produced similar relationships as Nmin. The regression analysis suggested that 40–90% of Nmin above a specific amount, 14–35 kg N/ha (interception of regression line, I1), on farms was apparently lost from the soil zone. Corresponding results for pooled data (n = 187) were 74% and 25 kg N/ha (r = 0.90, P < 0.001). The proportion of N leached from the 0–60 cm layer, calculated with a simple leaching equation was significantly correlated (n = 187, r = 0.92, P < 0.001) with observed Nminchange during winter, with the intercept (I2) significantly different from zero (–30.9 kg/ha). When the average value of regression intercept I1 of farms, or of pooled data, were introduced to the leaching equation as a constant correction parameter, the fit was satisfactory (r = 0.93 and 0.92, resp.) and the intercepts (–3.1 kg and –5.4 kg N/ha, resp.) were not significantly different from zero (at P < 0.01). The results of the study support the use of autumn Nmin within the leaching equation as a robust indicator of the risk of N leaching.Keywords:
Nmin; nitrate; risk; leaching equation; soil; precipitation; farms