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The effects of basil (Ocimum basilicum L.) on soil organic matter biodegradation, nutritional mineral elements and bacterial colonies were studied in the laboratory. The air-dried basil plant tissues incorporated at five different rates (0, 1, 2, 3, and 4 g per 50 g of soil) resulted in increases in organic carbon mineralization, mineral nitrogen forms in organic phosphorus and available potassium. The level of available forms of manganese and zinc was increased at all the rates of added basil whereas copper was increased at the two upper rates. Also, the addition of basil resulted in a decrease in soil bacterial colonies. The results of this study indicated that the basil could be used as a cover crop for suppressing weed or pathogens in organic soils, with a positive effect on soil productivity. In addition, the incorporation of basil in soil could reduce the number of bacterial colonies.

Gougoulias N., Papapolymerou G., Karayannis V., Spiliotis X., Chouliaras N. (2018) The effect of the algal species Chlorella vulgaris at six different ratios (0, 1, 2, 3, 4, 5 g) of air dried algae biomass, mixed with 10.18 g of sheep manure, added to 50 g of soil, and incubated for a period of 15 weeks was studied in a laboratory in order to detect the role of adding small amounts of admixed algal biomass to soil in biodegradation of soil organic carbon. The obtained data showed that mineralization of soil organic carbon increased by 16.2-35.9% at all rates of algae addition compared to the control, while the highest increase was observed at the highest rates of algae addition. There was a 40-50% increase in the available form of potassium, while the highest increase was also observed at the highest rates of algae addition. The four times higher rates of added algae increased the corresponding content of nitrate nitrogen by 20-30%, while ammonium nitrogen contents decreased by 9.5-35.7% for all amounts of added algae in comparison with the control. The available forms of copper, manganese, and zinc were also increased for all amounts of added algae by 56.8-61.9%, 55.8-67.3%, and 34.1-40.6%, respectively. On the contrary, the addition of algae did not indicate significant differences among treatments as concerns organic or available phosphorus contents. The results proved the effect of the algae Chlorella vulgaris as an accelerator agent in biodegradation of soil organic matter, without any significant negative impact on soil chemical properties.

A 2 year field experiment was conducted in northern Greece to study the biomass effects of four oregano (Origanum vulgare) biotypes, used as incorporated green manure, on the emergence and growth of barnyard grass (Echinochloa crus-galli), bristly foxtail (Setaria verticillata), common purslane (Portulaca oleracea), cotton (Gossypium hirsutum), and corn (Zea mays). The oregano biotypes were selected on the basis of their high phenolic content. The phytotoxic potential of the oregano biotype extracts also was determined in the laboratory by using a perlite-based bioassay with cotton, corn, and barnyard grass. The bioassays indicated that the germination, root elongation, and fresh weight of cotton, corn, and barnyard grass were reduced by the oregano biotype extracts. In the field, the emergence of common purslane, barnyard grass, and bristly foxtail was reduced by 0-55%, 38-52%, and 43-86%, respectively, in the oregano green manure treatments, as compared with the oregano green manure-free treatments (the controls).At harvest, the cotton lint and corn grain yields in the oregano green manure treatments were 24-88% and 5-16%, respectively, greater than those in the corresponding green manure-free, weedy treatments.These results indicated that when the biomass of the oregano biotypes with a high phenolic content were incorporated into the soil as green manure, they could be used to suppress barnyard grass, bristly foxtail, and common purslane in cotton and corn and consequently to minimize herbicide usage.

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