Abstract
ABSTRACT: Onion is an important vegetable crop, predominantly grown under conventional tillage system management. Alternatively, the vegetable no-tillage system uses cover crops to form a residue layer, which improves soil physical, chemical, and biological attributes. Aiming to understand the interaction of mycorrhizal and non-mycorrhizal cover crops, phosphatase activity, and soil phosphorus availability and uptake by plants, a no-tillage vegetable production system experiment with onion was carried out in Ituporanga, Southern Brazil. The treatments were black oats (Avena strigosa); rye (Secale cereale); oilseed radish (Raphanus sativus); rye + oilseed radish; black oats + oilseed radish, and a control with spontaneous plants. Additionally, two plots, a conventional tillage system area and a forest, both adjacent to the experiment, were evaluated. We measured cover crop biomass, onion yield, acid phosphatase activity, and resin-extracted phosphorus in the soil, shoot and root phosphorus content, and root colonization in cover crops, spontaneous plants, and onions. The treatments with cover crops had the highest plant biomass in winter and onion yield. Available soil phosphorus and acid phosphatase activity were higher in no-tillage plots than in the conventional tillage system area. The presence of non-mycorrhizal oilseed radish was associated with decreased colonization of rye and onion roots by arbuscular mycorrhizal fungi. No-tillage areas with cover crops or spontaneous plants in winter accumulated more phosphorus than conventional tillage system areas. The conventional tillage system showed adverse effects on most soil attributes, as shown by a Principal Component Analysis.
Highlights
Onions are among the most commonly grown vegetables worldwide
The total yield of onion bulbs ranged from 6.9 Mg ha-1 for spontaneous plants to 13.9 Mg ha-1 for black oats (Table 1)
The treatments previously sown with black oats and black oats + oilseed radish had higher onion yields than the other treatments
Summary
Onions are among the most commonly grown vegetables worldwide. Crop management predominantly uses conventional tillage systems, with intensive use of pesticides and highly soluble fertilizers (FERREIRA et al, 2018). As an alternative to the conventional tillage system, our team has been developing a vegetable notillage system for different plant species (FAYAD et al, 2019). It follows ecology-based principles, such as reduced soil tillage, split fertilizer application, and avoidance of highly soluble fertilizers. The vegetable no-tillage system uses cover crops to form a layer of plant residues on the soil surface and minimize tillage. In addition to changes in nutrient concentration in the upper layers, cover crops promote changes in soil structure (SANTOS et al, 2018), reduction of erosion processes (COMIN et al, 2018a), as well as increased soil biological activity and organic matter concentration (DE PONTES et al, 2017). Biological indicators can be used by technicians and farmers to monitor soil quality
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