THE FUNCTIONAL STATE OF THE ORGANIC MATTER OF GRAY FOREST SOIL UNDER DIFFERENT FERTILIZER SYSTEMS OF THE CROPS
The influence of mineral, organic and organomineral fertilizing systems on the content of active organic matter in the gray forest soil was determined as well as the ratio of the easily (k <sub> 1 </sub> > 0,1 day <sup> -1 </sup> ), moderate (k <sub> 2 </sub> > 0,01 d <sup> -1 </sup> ) and hard mineralizable (k <sub> 3 </sub> > 0,001 day <sup> -1 </sup> ) fractions in soil organic matter was assessed and compared to fallow sites. The contents of total and active organic matter in the arable soil were 1,3 and 1,9 times lower than in non-arable soil. The highest content of active organic matter was found in the arable soil under organic fertilizing system, while the smallest content was in the ridges of vegetable crops cultivated by the Mittleider method with intensive usage of fertilizers. The active organic matter pool of fallow soil and arable soil under organic fertilizer system was represented by three fractions, whereas the soil with the organomineral and mineral fertilizer systems were characterized only by easily and hard mineralizable fractions. Thus, there is a lack of active organic matter in the gray forest soil with mineral fertilization, which is partially possible to solve by the use of organomineral system. Increasing in the active organic matter in arable soils is achieved by using organic fertilizer system or by converting of arable soil to fallow land.