The role of macrosymbiont genotypes and earthworms in the enrichment of soil with biological nitrogen

Abstract

The specific features of the symbiotic apparatus and the accumulation of the plant biomass under the influence of different genotypes of peas (Pisum sativum L.) on gray forest soils were studied in field conditions. With the alternation of legume and grass cultures, the genotypes of plants with supernodulation were found to affect the microbial nitrogen content in the soil to a greater extent than the concentration of ammonium and nitrate nitrogen. For the growing period, the N content in the microbial biomass increased, on the average, by 1.3 to 1.5 times. The consumption of nitrogen by the plants of the supernodular mutant K-301a was found to be 2.6 and 3.0 times greater than that by the pea plants of the Ramonskii-77 variety and of the K-562a line, respectively. During the after effect of the symbiotically bound air nitrogen, a significant uptake of this element was observed only by the oat plants grown after the K-56 2a. The nitrogen fixation by these plants was 1.3 times more active than that by the peas of the Ramonskii-77 variety. The importance of earthworms (Lumbricidae) and plant residues of different genotypes for the processes of mineralization of organic compounds and accumulation of ammonium, nitrate, and microbial nitrogen in the soils under optimal hydrothermal conditions was revealed. In the experiment, two maximums of the CO2 emission were recorded; they may be related to the periodic production of organic mass by the earthworms and the creation of favorable conditions for microbial activity by them. The accumulation of nitrate nitrogen (up to 150 mg/kg) in the soil was the greatest owing to the interaction between the earthworms and the residues of the supernodular K-301a mutant.