The effect of long-term fertilizer application on the group and fractional composition of humus in a soddy-podzolic light loamy soil

The effect of lime and organic and mineral fertilizers on the fractional and group composition of the humus in a light loamy soddy-podzolic soil was studied in a long-term experiment. The application of lime increased the content of the agronomically valuable fraction of humic acids (HA-2) by 2.6 times on the average. The application of mineral fertilizers at the rate of N83P61K112 (kg/ha per year) increased the mobility of the humic substances; the application of farmyard manure (12.5 t/ha per) has an opposite effect. In general, various fertilizer systems exerted a favorable effect on the qualitative composition of the humus with an increase in the percentage of humic acids, though the humate-fulvate type of humus was preserved in all the variants of the experiment.