Site specific management in an olive tree plantation

Yield and soil mapping were carried out in 2007 and 2008 in a 9.1 ha commercial
olive tree plantation for olive oil production. The orchard is in the southern
Peloponnese, where olives are cultivated extensively for extra virgin olive oil production.
The field is planted in rows with about 1650 trees in total. Weed control was practiced
during the previous 3 years using post emergence herbicides under no-tillage over about
2/3 of the field, and over the remaining 1/3 by mechanical weeding using a rotary cultivator.
For yield mapping, olives were collected manually using rods to shake the tree
shoots and letting the olives fall onto a plastic net covering the ground. Sacks of
approximately 58 kg capacity were filled with olives from as many adjacent trees as were
needed to fill a sack. The location of the sacks, or group of closely placed sacks, was
identified using a commercial GPS (5 m resolution). In addition, 91 cores of soil were
taken at a depth of 0–30 cm on a 30-m systematic sampling grid corresponding to a density
of 10 soil samples per ha. The soil properties measured were penetration resistance, soil
texture, organic matter, pH, P, NO3–N, K, Mg, Zn, Mn, Fe, B and Ca contents. The effect
of the method of weed control on the soil condition for post emergence herbicides under
no-tillage versus rotary cultivation was evaluated on the basis of soil organic matter content and penetration resistance. The data were analyzed using both descriptive statistics
and geostatistical methods. Maps were created as a basis for site-specific management of P,
K and lime, and these were applied 15 days after harvest in the winter of 2008. The results
indicated considerable spatial variation in yield and soil properties. The soil organic matter
content was about 22% greater and the penetration resistance about 26% less in the areas
under no-tillage. The mean pH increased from 5.9 to 7.0 as a result of lime application in
the areas with pH below 6.5.