Cover crops may provide multiple benefits to soil protection, soil fertility, groundwater quality and pest management, especially in organic farming systems (1, 2) because of their potential role in reducing chemical inputs and improving soil quality. To reduce or eliminate the costs, many tree and vine crop growers prefer to use self-reseeding annual cover crops. In order to test the effects of Trifolium subterraneum L. cv. Clarè as cover crop on weeds, two experiments were carried out in Southern Sicily, in province of Caltanissetta (CL) in a 11-years peach orchard (37°12'55.3"N 14°05'28.3"E) and 3-years apricot orchard (37°13'36.0"N 14°05'02.4"E, 290 m a.s.l.), at a same planting density of 400 plant ha–1 (5x3 m tree spacing). At the start of the experiments, the soil was sampled and analyzed on macro and micro nutrients content, organic matter, total CaCO3 and pH, according to the Italian official methods (3). Therefore, the soil in peach orchard was sandy clay-loam and had a content of total N of 0,18%, organic matter 1,8% and total Ca carbonate 14%, phosphorus 82 p.p.m. and potassium 979 p.p.m; in apricot orchard the soil was silty clay-loam and had a content of total N of 1,1 g/kg, organic matter 19 g/kg, total Ca carbonate 61 g/kg, phosphorus 571 mg/kg and potassium 1,80%. For all the experiments, the study was conducted in an area of 1 hectare, four time replicated and arranged according to a randomised-block design. In order to intercept the major seed variability, every year in spring and autumn soil samples were collected in five different points, at the depth of 10 cm, using a metal probe of a 4 cm diameter. Until the beginning of the analysis, soil samples were stored for few days at 4°C in the dark. To separate soil from seeds, soil samples (four replicates of 150 g) were washed through a series of sieves (4). The extracted material was transferred into Petri dishes and was air-dried for the separation, identification and counting of the seeds with a binocular stereomicroscope (Olympus Optical Co, LTD). The two experimental field sites, despite being less than 2 km, were grown under very different conditions prior to these experiments, highlighting the importance of historical land use for the current weed seedbank. After the first year, significant differences in the qualitative and quantitative estimation of weed seedbank densities in the field experiments have been found. In peach orchard 5.200 seeds m-2 allowed to seven species, where Portulaca oleracea L., Amaranthus sp. and Setaria viridis (L.) P. Beauv. accounted for 80% of the total soil seedbank, vs 1.200 m-2 in apricot orchard allowed to only four species; in uncultivated plots, as control, seedbank was represented by 8.200 vs 3.600 respectively in peach and apricot orchards. Considering the effect of self-reseeding of T. subterraneum, only in the peach orchard after three years from seeding, weed seedbank was represented by 31.675 seeds m-2 allowed to sixteen species, where Amaranthus sp., P. oleracea, Lamium amplexicaule L., Helminthotheca echioides (L.) Holub, Veronica hederifolia L., S. viridis and Stellaria media (L.) Vill. were the main representative taxa. This result was in consequence to the effect that some cover crops may revert back to natural vegetation within a few years, so it may be necessary to resow the cover crop after three or five years. Managing the weed seedbank is a long-term effort, but it can supply long-term benefits. These three years of data can only serve as an early indication as to how different cover crops might influence the weed seedbank. Cover crop can contribute to reduce the size of the weed seedbank suppressing weed emergence, growth and releasing of seeds in the soil, so it represents a valid support for a sustainable weed management.
|Titolo:||The effect of cover crop on weed seedbank in Prunoideae orchards|
|Data di pubblicazione:||2016|
|Appare nelle tipologie:||4.2 Abstract in Atti di convegno|