Selection of shade-adapted subterranean clover species for cover cropping in orchards

Abstract

Agron. Sustain. Dev. 30 (2010) Abstract -The environmental side effects of intensive agriculture have underlined the need to develop sustainable farming systems. In particular, the use of cover cropping in orchards is a means of improving cash crop yield and of reducing the quantity of applied fertilisers. In the Mediterranean environment, subterranean clover species could be the best choice for cover cropping, but they are only poorly adapted to the heavily shaded conditions characteristic of modern high-density orchards. The plant traits needed to improve adaptation of subterranean clover are not well understood. Therefore, in a two-year experiment we studied the effects of four shading levels, of 0%, 40%, 60% and 90% reduction of photosynthetic active radiation, on phenology, growth and development of two subterranean clover species: Trifolium brachycalycinum cv. 'Clare' and T. subterraneum ecotype 'Ragalna'. Our results show that shading progressively delayed seedling emergence by up to 21 days, the initiation of flowering by up to 27 days, and the end of flowering by up to 25 days. Shading also lengthened the life cycle from 237 to 267 days. Shading reduced both soil cover by up to 38.2% and cover crop density by up to 39.7%. Shading lowered both the quantity of above-ground dry biomass by up to 820 g m −2 and photosynthetically active surface area by up to 213 cm 2 plant −1 . Trifolium brachycalycinum 'Clare' was more productive in terms of above-ground dry biomass yield, but T. subterraneum 'Ragalna' was better adapted to shading in terms of rapid emergence, earliness and the time taken to achieve soil cover. These species differences suggest that the breeding targets for improving the adaptation of subterranean clover to heavy shading are the ability to maintain earliness and the capacity to quickly break down hard-seededness under conditions of partial shade. A rapid initial increase in photosynthetically active surface area is particularly needed for maximising light harvesting during the early growth period.Trifolium brachycalycinum / T. subterraneum / cover crop / orchard / low irradiance

Effects of Shading on Chlorophyll Content, Chlorophyll Fluorescence and Photosynthesis of Subterranean Clover

“…These entries were chosen because of their rapid growth, their similar height (∼26 cm) but different leaf area (highest in ‘Clare’) and their ability to generate dense swards (Pardini et al. 1995, Mauromicale et al. 1997, 2010).…”

“…Over the last decades, subterranean clovers have attracted renewed attention for cover cropping in Mediterranean environments, as they rapidly achieve dense ground cover, show allelopathy against weeds and generate long‐lasting swards (Enache and Ilnicki 1990, Ingels et al. 1998, Mauromicale et al. 2010).…”

“…To provide most of the ecological benefits expected, cover crops must produce an adequate amount of biomass during their growth cycle, which, in turn, is the result of the species’ adaptation to the growth environment (Lu et al. 2000, Mauromicale et al. 2010).…”

Self-reseeding annual legumes for cover cropping in rainfed managed olive orchards

“…Persistence is also one of the key characters of sown legumes given the importance of self-regeneration of the sward to its economic viability. Previous studies using pasture legumes as cover crops are of great significance (Ovalle et al, 2007;Driouech et al, 2008;Mauromicale et al, 2010) but they are usually of short-term crops and have been focused on several aspects other than precocity or persistence of the sown species.…”

Cover Crops for Managing Weeds, Soil Chemical Fertility and Nutritional Status of Organically Grown Orange Orchard in Sicily

“…In this view, cover cropping has been proposed as a pivotal tool of improving agricultural sustainability, since in the soil it has the potential to mitigate compaction and erosion (Mitchell et al, 1999;Scopel et al, 2013), increase porosity (Carof et al, 2007), improve the ability to retain and remobilise nutrients (Doltra and Olesen, 2013), enrich organic matter content, especially in the case of legume species (Stagno et al, 2008), enhance the macrofauna activity (Blanchart et al, 2006), release non-available phosphorus (Kamh et al, 1999), stimulate the generalist predator arthropod populations and heartworm communities. Moreover, cover crops generally reduce pest and weed pressure on cash crops (Den Hollander et al, 2007;Hiltbrunner et al, 2007;Pelosi et al, 2009;Chen et al, 2011;Campiglia et al, 2012) and consequently, can also represent a key option in the agronomic management of orchards in Mediterranean-type environments (Mauromicale et al, 2010;Mauro et al, 2011Mauro et al, , 2014. However, these beneficial functions, particularly relevant under organic and lowinput cropping regimes, require a knowledge about the adaptability of the species for the different agro-ecological conditions, with special attention about the changes that occur on native flora, soil properties and fruit trees (Mauro et al, 2013).…”