EFFECTS OF CEREAL/LEGUME INTERCROPPING ON NITROGEN LEACHING: LYSIMETRIC FIELD EXPERIMENT

The paper presents a year’s summary (third year) of results of a long-term experiment which was established to examine the hypothesis that cultivation of a mixed culture of winter wheat (Triticum aestivum L.) and white clover (Trifolium repens L.) affects leaching of mineral nitrogen from the soil. The reason for the examination of this hypothesis is the increasing amount of mineral nitrogen in drinking water sources. The mixed culture or intercrop means the growing of two crops at the same time in the same place. In this case, the particular mixture consists of cereal/legume intercropping. A lysimetric field experiment was established to verify the hypothesis. Six variants were established in three repetitions. In two variants, only winter wheat with fertilisation (140 kg of N/ha/yr) and without fertilisation was grown. In the other four variants, winter wheat was grown alongside white clover (Trifolium repens L.) with the use of varying doses of mineral (DAM 390) and organic (Lignohumate B) fertilisers. Percolate leaching from the experimental lysimeters was collected and traps with ion exchange resin (IER) were placed in each container. The amount of ammonia (NH4+-N) and nitrate (NO3−-N) nitrogen in the water was measured regularly. The amount of trapped mineral nitrogen into the structure of from IER was also measured. A statistically significant difference (ANOVA; P < 0.05) was found between variant CY and all other variants. Of particular importance is the difference between variants CY and A1, since both were fertilised with mineral fertiliser only. From this, we can deduce that intercrop/mixed culture reduced the leaching of ammoniacal nitrogen from the system. A statistically significant difference (ANOVA; P < 0.05) was found between variant CY and A2 in the capturing of ammoniacal nitrogen (NH4+-N) from traps.