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Atucha A.,Colorado State University | Merwin I.A.,Cornell University | Brown M.G.,Cornell University | Gardiazabal F.,Sociedad Gardiazabal and Mena | And 4 more authors.
Functional Plant Biology | Year: 2013

The effect of groundcover management systems on root demography and distribution of newly planted avocado (Persea americana Mill) trees was examined using minirhizotron techniques. We evaluated three groundcover systems: (1) bare soil (BS), pre-and post-emergence herbicides; (2) vegetation strip (VS), post-emergence herbicide applied in a 1-m wide strip centred on the tree row plus a groundcover mixture seeded between tree rows; and (3) complete groundcover (GC), covering the entire surface of the plots. Root production was higher in the non-bearing year (2009-10) than in the bearing year (2010-11). Trees in the BS plots had more roots of bigger diameter in the top 30cm of soil and trees in VS and GC plots had more roots in the 30-60cm depth and of smaller diameter. Lifespan of spring-born roots were 61 and 59% greater than those born during autumn and summer, respectively and soil depth and root diameter were positively correlated with root longevity. Lifespan of thinner roots (<0.2mm) in the BS and VS plots were 49 and 33% greater than GC respectively. Avocado trees grown in contrasting condition compared with their native habitat show high morphological root plasticity, in response to resource and non-resource competition when grown in mixed stands. © 2013 CSIRO. Source


Atucha A.,Colorado State University | Merwin I.A.,Cornell University | Brown M.G.,Cornell University | Gardiazabal F.,Sociedad Gardiazabal and Mena | And 3 more authors.
Plant and Soil | Year: 2013

Aims: Assess the influence of different groundcover management systems on erosion and runoff processes associated with extremely steep hillside avocado (Persea americana Mill) orchards, in a Mediterranean climate with high rainfall variability. Methods: We compared several groundcover management systems at a steep hillside avocado planting in a three-year study: 1) Bare soil (BS), pre- and post-emergence herbicides; 2) Vegetation strip (VS), post-emergence herbicide applied in a 1-m wide strip on the tree row plus groundcover seeded between tree rows; 3) Groundcover (GC), over the entire plot surface. Results: Trees in the BS plots were 44 and 53 % bigger, and had 150 and 250 % higher yields than trees in VS and GC, respectively. Runoff volumes, soil losses, dissolved organic carbon, PO4-P and total N losses were significantly higher in BS than VS and CG treatments. Total soil nitrogen (N) and carbon (C) content, C-to-N ratios, and essential plant nutrient availability were greater in the GC soil than in other treatments. Soil macroporosity and aggregate stability were 8-27 % and 25 % lower, and soil bulk density significantly higher in the BS than the VS and GC systems at the end of the study. Terbuthylazine herbicide concentrations in runoff water from BS plots ranged from 55.4 to 79.9 μg L-1, exceeding maximum allowed levels for drinking water (0.1 μg L-1). Conclusion: Soil erosion and runoff rates from newly planted hillside orchards are not environmentally sustainable under current growing practices where groundcover vegetation is completely suppressed. High sediment losses and herbicide residues in runoff water present serious risk of water source pollution, but these impacts can be reduced by alternative soil management systems. © 2012 The Author(s). Source

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