Olive Nurseries Research Articles

Investigating the Possibility of Peat Substitution in Olive Nurseries by Green Compost

Peat is extensively used in olive nurseries as a primary coniponeTiFifrcommfercial soilless potting media. The increased use of peat as an organic amendment with superior water holding capacity is challenged by economic and environmental pressures. To stay competitive and satisfy environmental concerns, potential alternatives to peat need to be investigated. In the present investigation, commercially available peat-based soil- less mixes were amended with 25%, 50%, 75% or 100% organic green compost generated from biosolids. Results suggest that compost can be a viable partial alternative to peat as a substrate for containerized olive nur- sery production. Media amended with 25 and 50% compost provided plants with a better growth and appea- rance compared to unamended media. On the other hand, a higher compost content (75 or 100%), even though not affecting plant growth, improved plant susceptibility to water shortage. Green compost did not also impro- ve heavy metal content in plant tissues. Concluding, peat-based media partially amended with green compost may have positive agronomic and economic consequences for commercial olive nursery production.

Solarization of soil in piles for the control of Meloidogyne incognita in olive nurseries in southern Spain

The potential of solarization to control Meloidogyne incognita in piles of soil used at olive nurseries in southern Spain was studied in 1999 and 2000. Kaolin and soil infested with free eggs and egg masses of the nematode in nylon bags were buried 20 and 40 cm deep inside conical piles of soil 80 cm high and with a base diameter of 1 m. Soil piles were solarized for 3 weeks in July and August. The effect of various periods of solarization was assessed by egg hatch bioassays in sterile water, and by infectivity to tomato plants. Maximum soil temperature at 20 cm depth in solarized piles was 47·4°C in 1999 and 48·2°C in 2000, compared with 32·9°C and 31·7°C in nonsolarized piles. Solarization reduced egg hatch by > 95% compared with nonsolarized samples, irrespective of type, burial depth and location of inocula in a soil pile. Egg hatch of egg mass‐infested samples buried at 20 cm depth was higher than that of free eggs buried at the same depth. The differential effect associated with burial depth and type of inoculum was not found in solarized piles. In nonsolarized piles, hatch of free eggs from samples buried at 40 cm depth was higher than that from samples buried at 20 cm depth. Egg hatch in samples from solarized piles was lower than that from nonsolarized piles. A bioassay of tomato plants in 2000 confirmed the reduction in infectivity of free eggs buried in solarized soil piles. Under the conditions in southern Spain, solarization of 40 cm‐high piles of soil for 3 weeks can therefore be used for the control of root‐knot nematodes in potting soil for olive nursery production.

Effect of traditional and slow-release N fertilizers on growth of olive nursery plants and N losses by leaching

‘Picual’ olive trees ( Olea europaea L.) growing in 3 l plastic pots were fertilized with traditional or slow-release N fertilizers to study their growth and to determine N leaching losses. The traditional N fertilizers used were urea, ammonium sulfate, ammonium nitrate, and calcium nitrate; the slow-release N fertilizers selected were a sulfur-coated urea (Greenmaster), a nitrification inhibitor (Basammon), a low solubility material (Floranid), and a resin-coated urea (Multicote). Each plant received 2 g N from one of the aforementioned N fertilizers at the beginning of a first experiment, and 0.75 g N in a second experiment. Fertilized plants showed significantly increased vegetative growth compared to controls, but plants fertilized with 0.75 g N exhibited a greater shoot growth than those that received 2 g N. No significant differences were found among fertilizers when 0.75 g N was applied, but greater growth was obtained with Floranid and Multicote when 2 g N was applied to each plant. Regardless of N formulation, N was accumulated mainly in leaves of the olive plants. Most of the N recovered in the leachates was in the nitrate form. Total N losses were higher when ammonium nitrate and calcium nitrate were applied, and lower with the slow-release fertilizers, except for Basammon.

PARASITIC NEMATODES ASSOCIATED WITH OLIVE IN COUNTRIES BORDERING THE MEDITERRANEAN SEA

PARASITIC NEMATODES ASSOCIATED WITH OLIVE IN COUNTRIES BORDERING THE MEDITERRANEAN SEA

Incidence and Population Density of Plant-Parasitic Nematodes Associated with Olive Planting Stocks at Nurseries in Southern Spain.

Nematode population densities were determined in 259 soil and root samples collected from 18 olive nurseries in Córdoba, Jaén, and Sevilla provinces (southern Spain), between October 1997 and May 1998. The most important plant-parasitic nematodes detected, in order of decreasing frequency of infestation (percentage of samples), were Mesocriconema xenoplax (39.0%), Pratylenchus penetrans (32.1%), P. vulnus (25.9%), Meloidogyne incognita (14.7%), M. javanica (11.2%), and M. arenaria (2.7%). No disease symptoms were noted on aboveground organs of infected plants. However, population densities of Pratylenchus and Meloidogyne spp. were at potentially damaging levels in most of the olive nurseries surveyed. Histopathological studies of galled roots from the naturally infected olive planting stocks showed a susceptible response to root-knot nematode infection. Large numbers of egg masses were present within the galled root tissues that might contribute to secondary infections. Feeding by root-knot nematodes induced the expected cellular alterations in the cortex, endodermis, pericycle, and vascular system, including giant-cell formation and the alteration of vascular tissues.

Spread of verticillium wilt by nursery plants in olive groves in the Halkidiki area (Greece)1

Olive groves have been established during the last decade in the coastal area of Halkidiki and in the northern part of the Kassandra peninsula (GR). Visual symptoms of verticillium wilt were observed recently all over this area, particularly in young trees of cv. Hondrolia Halkidikis but not in the occasional old trees already in the orchards. The symptoms appeared regardless of the previous crop (cotton or not), so the nurseries supplying the farmers with young trees were assumed to be the primary source of infection. A survey of olive nurseries in the area was conducted during 1991. Eleven out of the total 18 nurseries in the area were located in the Verticillium dahliae‐infested zone and 9 of these were sampled. Three‐year‐old olive seedlings were selected and isolations were made from the xylem onto PDA acidified with 0.25% lactic acid. V. dahliae‐infected seedlings were detected in 4 out of the 9 nurseries examined. The presence of infected young trees in nurseries covering 15.6% of the total nursery area provided strong evidence that nurseries may be responsible for the recent expansion of verticillium wilt in the area.