Impact of different soil management on soil microbial community

Agricultural practices greatly influence soil chemical properties and the microbial population, which plays a fundamental role in developing a good soil structure through the binding of soil aggregates by hyphae and by secretion of microbial exudates. The aim of the study was to investigate the effects of different tillage (conventional (CT), minimum (MT) and no tillage (NT)), fertilization (fertilization versus no fertilization), soil depth (0-30, 30-60, and 60-90 cm) and crops (wheat versus faba bean) on the abundance of the soil microbial bacteria, fungi and yeasts. Another objective was to understand which variables were the most responsible for the growth of the microbial population and the correlations existing between the chemical and microbiological soil parameters. Positive and significant correlations were found between total microbial population and bacterial and fungal populations. This result suggested a predominance of fungi and bacteria in the microbial community composition, compared to the yeasts which were a minority. The total microbial population was positively correlated to the content of soil organic carbon, total nitrogen and available phosphorus and negatively correlated to soil pH. With regards to tillage, MT seemed the best solution in terms of abundance of microbial population, representing a good compromise between soil aeration and available nutrients. The faba bean was the crop that favored more the microbial community due to its nitrogen fixing feature. The statistical analyses showed that depth was the parameter that mainly influenced the chemical and, consequently, microbiological properties of soils.