Nitrate Dynamics in Soils after Potatoes S20
Reents, H. J.1 & Möller, K.2
1) Coordinator for Ecological Agriculture and Gardening,Technical University Munich(TUM)-Weihenstephan, D-85350 Freising; 2) Chair for Phytopathology, TUM-Weihenstephan
|The object of the field experiment was to
investigate how different management systems reduce nitrate in soils and prevent leaching
during the winter after harvesting potatoes and how they effect yields and product
quality. At the beginning of September the potatoes were harvested, then the field was
ploughed. The treatments afterwards were as follows:
WwSep: winter wheat »Bussard« sown Sep 19th;
WwOct: winter wheat sown Oct 14th;
WwNov: winter wheat sown Nov 3rd;
Mus.+Ww: mustard seed (Sep 19th) and drilling winter wheat in the growing catch crop on Oct 14th;
Mus.+Sw: mustard seed as catch crop Sep 19th, summer wheat »Nandu«, sown Mar 14th; and
Fall.+Sw: fallow, summer wheat sown Mar 14th.
Results: The results of the nitrate tests on Dec 16th showed that up until that time there was not any noticeable nitrate leaching, but only movements within the soil profile (90cm). When compared to the results of December the soil nitrate content on Mar 15th showed a decrease of about 20 kg N/ha on the fallow plots and is interpreted as being an effect of leaching. WwNov showed a similar leaching rate, with the rate of WwOct being even lower.
The nitrate quantities detected in April in the soil layer between 90-150cm confirmed the effect of the different treatments but were higher than calculated by the difference method.
WwSep and the combinations with mustard seed as a catch crop clearly reduced nitrate content in the soil and prevented leaching. Both Mus.+WW and summer wheat yielded significantly lower amounts.
Winter wheat yields without catch crop differed only a little with the WwOct having the highest yield. Mus.+WW had significantly lower yields. WwNov showed the highest N-uptake and the best quality, so it is presumed that during the graining stage the roots reached the leached nitrate in the soil layer below 90cm.