This study was based on a three-factor experiment carried out since 1980 on a loamy sand (Albic Luvisol) in which arable crops were grown in two 4-years rotations: RotA (grain maize, winter wheat, spring barley and silage maize) and RotB [grain maize, winter wheat plus mustard green manure (GM), spring barley and grass–clover ley (GCL)]. The soil in RotB with an increased input of OM (GM and 1-year GCL) accumulated significantly larger amounts of soil organic carbon and soil microbial biomass C, had higher activities of dehydrogenase and acid phosphatase enzymes and gave significantly higher winter wheat grain yields compared to the soil in RotA. However, in the absence of liming, the soil in RotB, contrary to that in RotA, became more acidic, had reduced activity of alkaline phosphatase and lower contents of Ca and Mg, and contained a diminished proportion of the >0.5 mm macroaggregates fraction. These soil deteriorative effects of crop rotations delivering larger amounts of OM have not been reported so far. In both rotations FYM applied once per 4-year rotation at 40 Mg ha⁻¹ improved all the tested soil properties and had mitigating effects on the negative changes found in the soil of RotB.

Liquid media containing potato extract and 1% of glucose or sucrose were used to culture root-nodule bacteria (rhizobia) in shaken Erlenmeyer flasks. For comparison, these bacteria were also cultured in yeast extract-mannitol broth (YEMB) as a standard medium. Proliferation of rhizobia was monitored by measuring optical densities (OD550) of the cultures and by plate counting of the viable cells (c.f.u) of the bacteria. In general, multiplication of the rhizobia in potato extract-glucose broth (PEGB) and potato extract-sucrose broth (PESB) was markedly faster, as indicated by higher values of OD550, than in YEMB. The numbers of R. leguminosarum by. vicae GGL and S. meliloti 330 in PEGB and PEGB were high and ranged from 1.2 x 10(10) to 4.9 x 10(10) mL(-1) after 48 h of incubation at 28 degrees C. B. japonicum B3S culture in PEGB contained 6.4 x 10(9) c.f.u. ml(-1) after 72 h of incubation. PEGB and YEMB cultures of the rhizobia were similar with respect to their beneficial effects on nodulation of the host-plants of these bacteria.

In micro-plot experiments growth, nodulation and seed yields of pea, yellow lupine and soybean grown in a soil colonized by high populations of pea and lupine rhizobia and low population of soybean rhizobia as influenced by seed or soil application of rhizobial inoculants were studied. The studied inoculation method had no significant effects on root nodule numbers, plant growth at the flowering stage and on seed yields of pea and yellow lupine in comparison to uninoculated control treatments. In the case of soybean seed and soil inoculation with soybean rhizobia (Bradyrhizobium japonicum) resulted in a significant increase of nodulation intensity, fresh and dry mass of shoots at the flowering stage as well as pod numbers and soybean seed yields at harvest. Soybean grown on plots in which soil was inoculated with the symbiotic bacteria gave seed yield by about 57 % higher as compared to that of soybean grown from seed inoculated with the rhizobia and by 169 % higher than when this crop was grown on the control (uninoculated) plots.

The aim of this study was to compare contents of labile fraction of soil organic matter and microbial parameters in soil under winter wheat and spring wheat grown according to organic, without animal manure application, and conventional crop management systems. Particulate organic matter fraction in the organically managed soil was significantly higher by 26% than that in the soil under the conventional farming system. Culturable colony forming units of bacteria and fungi, dehydrogenase and alkaline phosphatase activities, as well as C contents in microbial biomass and in hot water extracts (HWE) were significantly higher for the organic soil than for the conventional system. HWE prepared from both soils contained almost the same amounts of total N, but microbial biomass-N was higher in the organic soil. These results indicate that organically managed soils can maintain a high biological activity and substantial pools of readily available nitrogen even without application of animal manures.