Cover crops for the improvement of soil microbiological properties in intensive horticultural production systems

Abstract

The production of horto-industrial crops in the Portuguese region of Ribatejo is based on monoculture systems with high technical intervention, which results in soil biodiversity imbalances, loss of fertility and progressive degradation. In these systems, the introduction of cover crops preceding the main crop of the agricultural year can contribute to improving the soil status and the sustainability of the production systems. The present work describes the evaluation of soil microbiological indicators in two field trials in Ribatejo, where different cover crops were installed: biodiverse mixture of legumes and grasses, including clovers inoculated with rhizobia; annual ryegrass (Lolium multiflorum); and forage turnip (Raphanus sativus) for biofumigation. Control plots without cover crops were maintained in both fields. The evaluations focused on soil enzymatic activities (dehydrogenase, alkaline phosphatase and β-glucosidase) and several groups of microorganisms, including total bacteria, symbiotic nitrogen-fixing bacteria (rhizobia), free-living nitrogen-fixing bacteria, phosphate-solubilizing bacteria and phytostimulating microorganisms. The results indicated a tendency for the increase of soil microbiological activity and beneficial microorganisms with cover crops, especially with the biodiverse mixture of legumes and grasses and annual ryegrass.