Cover Crops Effects on Soil Chemical Properties and Onion Yield

Abstract

ABSTRACT:Cover crops contribute to nutrient cycling and may improve soil chemical properties and, consequently, increase crop yield. The aim of this study was to evaluate cover crop residue decomposition and nutrient release, and the effects of these plants on soil chemical properties and on onion (Allium cepa L.) yield in a no-tillage system. The experiment was carried out in an Inceptisol in southern Brazil, where cover crops were sown in April 2012 and 2013. In July 2013, shoots of weeds (WD), black oats (BO), rye (RY), oilseed radish (RD), oilseed radish + black oats (RD + BO), and oilseed radish + rye (RD + RY) were cut at ground level and part of these material from each treatment was placed in litter bags. The litter bags were distributed on the soil surface and were collected at 0, 30, 45, 60, 75, and 90 days after distribution (DAD). The residues in the litter bags were dried, weighed, and ground, and then analyzed to quantify lignin, cellulose, non-structural biomass, total organic carbon (TOC), N, P, K, Ca, and Mg. In November 2012 and 2013, onion crops were harvested to quantify yield, and bulbs were classified according to diameter, and the number of rotted and flowering bulbs was determined. Soil in the 0.00-0.10 m layer was collected for chemical analysis before transplanting and after harvesting onion in December 2012 and 2013. The rye plant residues presented the highest half-life and they released less nutrients until 90 DAD. The great permanence of rye residue was considered a protection to soil surface, the opposite was observed with spontaneous vegetation. The cultivation and addition of dry residue of cover crops increased the onion yield at 2.5 Mg ha -1 .

Release of Phosphorus Forms from Cover Crop Residues in Agroecological No-Till Onion Production

“…This is because most of the P in plant tissue is found in inorganic forms (Casali et al, 2011;Marschner, 2012) and the inorganic P in the tissue makes up the labile compartment. These results corroborate with those obtained by Fernandes et al (2000), Pereira et al (2008), Casali et al (2011), and Oliveira et al (2016), who noticed that most of the tissue P is found in the soluble inorganic form in well-nourished plants grown in soil with sufficient nutrient content.…”

“…This is due to the difference in accumulation of P forms in the tissue. It indicates that the P release rate depends not only on total content in the tissues (Oliveira et al, 2016), but also on how P is stored, in addition to other characteristics of the residue, such as C/N ratio (Tables 1 and 4) and leaching of water-soluble compounds degraded by the microbial population of plant residues (Ferreira et al, 2014). According to Aita and Giacomini (2003), this is because most microorganisms, especially fungi and bacteria, which colonize plant residues and part of total soil organic C, are used during decomposition as a source of ATP and are in part released into the atmosphere in the form of CO 2 (Manzoni et al, 2008).…”

“…This is similar to results observed by Casali et al (2011), who compared the release of P forms in black oat, vetch, and forage turnip residues in an experiment conducted in an Oxisol under no-tillage and conventional tillage. Furthermore, the predominance of P-RNA after 15 DAD in AV residues depends on its mineralization and release of P, with consequent uptake by the onion root system (Oliveira et al, 2016).…”

Carbon and nitrogen content in granulometric fractions of organic matter in soil aggregates under no-tillage and conventional tillage planting systems for onions

“…The low POC value found in the surface soil layer (0-5 cm) of plots with oilseed radish may be due to the lower lignin and higher cellulose content of this species compared to the other cover plants (Oliveira et al, 2016). Consequently, they decompose more quickly and result in lower soil POC content.…”

“…Intercropping black oats with oilseed radish, which has an axial root and a deep root system, promotes physical and chemical effects in depth. The combination favors soil aggregation as well as carbon increase and protection in aggregates, in this case POC, since this fraction is directly related to plant material recently added to the soil (Loss et al, 2015;Wick et al, 2014;Oliveira et al, 2016).…”