D. STOICHEVA, P. ALEXANDROVA, D. DONOV, D. STOICHEV , G. ANGELOV and L. RAIKOVA
N. Poushkarov Institute of Soil Science, BG-1080 Sofia, Bulgaria
STOICHEVA, D., P. ALEXANDROVA, D. DONOV, D. STOICHEV, G. ANGELOV and L. RAIKOVA, 2002. Ecological assessment of different nitrogen fertilizer rates in a vegetable crop rotation. Bulg. J. Agric. Sci., 8: 141–150
Influence of different nitrogen forms, rates and ways of application, on the yield, nitrogen content in the soil, soil solution, lyzimetric and groundwater, as well as nitrate content in plant production has been studied in a field experiment with potatoes, cabbage and lettuce. It was established that the climate conditions were not a limitation factor for the vegetable crops development.
Data show that the soil solution composition is the most susceptible characteristic, which reflects the changes in the solid soil phase under anthropogenic impacts. A certain increase of nitrate-nitrogen content in 0–100 cm soil layer with split application of ammonium nitrate was observed. These differences are logically conditioned and could be attributed to the specific behaviour of urea and ammonium nitrate in the plant-soil system. Throughout the whole year from the experimental area, there was formed groundwater with nitrate content higher than the maximum concentration limits for drinking water.
It was made the assumption that potatoes, cabbage and lettuce growing in the vegetable rotation is a suitable technological decision, which guarantees maximum inclusion of nitrogen in the biological cycle of nutrients and prevention of residual nitrogen accumulation in the soil profile.