The changes of mineral nitrogen content in clay loam Cambisol in sustainable and organic agriculture

Experiments were conducted in the Joniskelis Experimental Station of the Lithuanian Institute of Agriculture in 2006-2008 on the clay loam Gleyic Cambisol. The aim of the research - to estimate changes of amount of mineral nitrogen in several humus content soils under influence of fertilization systems with a catch crop of green manure - combinations of white mustard (Sinapis alba L.), oil radish (Raphanus sativus L.), narrowleaf lupin (Lupinus angustifolius L.), buckwheat (Fagopyrum esculentum MOENCH.) in sustainable and organic farming systems. Experiments showed that in late autumn, before incorporation of different catch crops biomass, the lowest amount of mineral nitrogen - 6.21-6.31 mg kg -1 in the soil layer of 0-40 cm was found in the organic farming system. In the sustainable farming system growing white mustard and using nitrogen at low rates - N 30 for more intensive straw mineralization, the amount of mineral nitrogen in the soil was significantly - 17.0-15.2% -higher. The highest content of mineral nitrogen - 8.04 mg kg -1 in the soil was found in the fields without catch crops, where N 30 was also applied for straw mineralization.