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.
Effects of pre-sowing soybean seed inoculation with Bradyrhizobium japonicum alone or with mixed inoculants containing soybean rhizobia and Azotobacter chroococcum were compared. In the pot experiment all the tested strains of soybean rhizobia in pure cultures or in mixtures with A. chroococcum significantly improved nodulation of soybean plants and seed yields of this crop. In micro-plot experiments pre-sowing soybean seeds treatment with the inoculant containing the most effective strain 94P of B. japonicum alone or with the mixed inoculant of strain 94P and A. chroococcum were equally effective in improving nodulation intensity and seed yields of soybean in comparison to the uninoculated soybean.
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.
Martyniuk S., Jończyk K., Kozieł M. 2019. Phosphate solubilizing microorganisms and phosphatase activities in the rhizosphere soil of organically grown winter wheat cultivars.
AbstrActIn 2014-2016, eleven commercial winter wheat cultivars, released between 2008 and 2011, were organically grown in a field experiment at Osiny Experimental Station (51°28′N, 22°30′E). Each year in the first or second ten days of May, samples of rhizosphere soil were analyzed for numbers of colony forming units (CFU) of phosphate solubilizing microorganisms (PSM) and for acid (AcP) and alkaline phosphatase (AlP) activities. At the same sampling days in the May of each year, winter wheat tillers at shooting (GS 35-40) were collected to determine the total P content in plant tissues, while grain yields were measured at full ripeness of winter wheat. Relationships between the microbial and enzymatic parameters, wheat grain yields and plant P content were also analyzed. Under organic farming the tested winter wheat cultivars differed markedly with respect to their grain yields and P acquisition in particular years, although none of these cultivars showed superior performance across all years. In 2014, significant correlations were found to occur between CFU numbers of PSM and activities of alkaline phosphatase (AlP), between grain yields and AlP activities and between plant P content and PSM numbers. In 2015 and 2016, significant correlations, r = 0.611 and r = 0.630 respectively, were found only between the CFU numbers of PSM and grain yields of the examined cultivars, indicating that phosphate solubilizing microorganisms and their activity can play an important role in the performance of winter wheat cultivars under organic farming.
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