EFFECTS OF FERTILIZATION IN LONG-TERM TRI ALS ON BROWN FOREST SOIL ATGODOLLO .3. SOIL PROPERTIES

On brown forest soil at Godollo a multifactorial fertilization long-te rm plot trial has been carried out since 1972. The authors have alread y reported on the method, conditions and main agronomic experiences of the first two decades in part I of their paper (Yield of arable crops ), while on the effect of the long- term trial on the nutrient content of winter wheat, maize and potato in part II (Plant nutrient contents ). In the present paper the effect of long-lasting fertilization with growing rates and that of the provisional interruption of fertilizatio n was studied on the soil properties including soil fertility, in the first place on its readily soluble nutrient content, nitrogen mobility , change in its chemical reaction. The organic matter content of the f ertilized soil has also been investigated. As affected by systematic N PK fertilization over 14 years, and by rising rates of active agents ( 0-900 kg ha-1 year-1), the soil became more and more acidic (up to pH( KCl) 3.7). The decrease in chemical reaction was incident to the reduc tion of calcium and magnesium and to the provable increase of sulphate content in the ploughed layer. The nitrate-nitrogen quantities origin ating from the N-fertilizers were provable present not only in the cul tivated soil layer, but also in the deeper (2-3 m) one to a greater ex tent. The NO3-N concentration was the highest in the soil-layer of 140 -160 cm. It can be stated, based on the soil sample test results of th e long-term trial that the prolonged fertilization with low and medium rates, applied systematically or year after year periodically every t hird year, ensures a rate of replenishment of forest soils Godollo, to provide a good nutrient supply. Over- fertilization exceeding this ra te is not only economically useless, but it is wrong from agrochemical aspect, because it may cause a failure in the efficiency of fertiliza tion, an enrichment of plant nutrient-carrier and accompanying ions up to the toxical level, a strong acidification of soil or even the poll ution of subsoil, ground water and surface waters. The results of soil studies are unambiguous with the agronomic experiences of the trial, to which they serve as explanation, as well. The organic matter replac ement was limited in 1972-1986 only to the root and stubble residues. So the dominant effect of fertilization realizing decisively mineral e lement replacement showed itself that the initial humus content of the soil significantly decreased by 0.2-0.3 absolute percent within 14 ye ars. The decrease in chemical reaction manifested in plots without any fertilization proved that the soil acidification in the trial as a wh ole can be explained also with atmospheric reasons besides fertilizati on. The experiences support the claim that besides the supply of the s oil with the most impotent mineral nutrients, more attention should be paid in the future, to the organic matter economy and lime fertilizat ion with a view of preserving and increasing the soil fertility.