CEREAL CROP RESIDUE AS AN ALLELOCHEMICAL SOURCE AND THE IMPORTANCE OF MINERAL FERTILIZERS IN ITS DEGRADATION

Abstract

The authors has made several experiments, in pots and in the field, for studying the effect of wheat and barley straw applied in soils in normal and excessive quantities over the growth of bean, beet and parsley. The experiments showed that when applied in a dosage of over 9 t/ha the straw represented an important source of allelopathic compounds, that significantly decreased the crop yield This decrease was not accompanied by a decrease in the N % percentage in plants, as it usually happens in the case of N deficiency in nutrition, but, on the contrary, the N % content increased while the crop yield decreased. The conclusion was that the yield decrease due to large amount of straw applied to the soil was not generated by N deficiency in nutrition, but to the antiauxinuic action of allelochemicals at root level The N fertilizer favor microorganism’s development and decompose allelochemicals in order to obtain the carbon necessary for their growth Rhizobium was more sensitive at the noxious action of allelochemicals, as compared to the host plant. Cereal crop residue increased the N and organic carbon content in soil and K accessibility.