Effect of mineral fertilizers and liming on fractional group composition and optical characteristics of humic acids of sod-podzolic heavy loamy soils of Pred-Urals
E-mail: pniish @ rambler.ru
Effect of mineral fertilizers and lime on fractional group composition and optical characteristics of humic acids (HA) of sod-podzolic heavy loamy soil was studied in a stationary field experiment. It was established that the prolonged use of mineral fertilizers (at rate 2NPK) leads to increase of carbon content in the mobile fraction HA-1 up to 12.4 % compare to the total carbon amount. Liming facilitated the accumulation of humic acids associated with calcium in humus complex of sod-podzolic soil. The maximum amount of humate type humic substances is found in repeatedly limed soil on 2NPK background; the CHA : CPA ratio is 0.96. The humus type is fulvic-humate. The soil liming promoted the formation of a more "mature" and optically dense HA. Humic acid solutions of all three fractions extracted from the limed soil have high values of the extinction at 465 nm, which indicates a high content of aromatic structures in the molecules of HA. The humic substances solutions (fraction HA-1, variant 2NRK, E465 = 3.05) are characterized by the minimum value of the optical density. The mineral fertilizers and lime have less impact on humic substances of the third fraction strongly bound to the mineral part of the soil.
Keywords: sod-podzolic soil, mineral fertilizers, lime, humus fractions, absorption spectrum, extinction