MINERAL AND ORGANIC FERTILIZATION OF THE HAZELNUT (CORYLUS AVELLANA), IN CENTRAL ITALY.
The same unities of fertilizers were distributed (200 – 100 –150 for nitrogen, phosforous and potassium). The experimental plan in random blocks was based on a comparison of the three different treatment repeated ten times on single plants.
Final analysis of the soil showed that the different types of fertilizers did not influence the texture and modified the pH only slightly. In addition the lowest nutritional values were found in the non fertilized treatment; the highest in the organic-mineral fertilized one.
The development of the plants, measured from the final diametre of the trunk, did not show significant differences in the fertilized plants, but they were better developed than the non fertilized test plant.
During the first two years of the trial the average production per plant did not show any difference between the fertilized and not fertilized but, from the third year on, production of the non fertilized plant was inferior in comparison to the other two which had similar productions. There were significant differences in the cumulative production of the fertilized plants which was higher than in the non fertilized. The lowest value in the five year average weight of the nutlets resulted in the organic mineral fertilization but it showed, at the same time, the highest values in respect to the number of nutlets from infructescence.
The different treatments did not influence either the calibre of the nutlets or their diametrical comparison, or their roundness (which all remained typical for the cultivar being tested). The different treatments also did not influence either the five year average weight of the seeds, or the percentage yield of the shelled fruit, or the percentage of empty shells.
The values of the leaf analysis show that the plant treated with organic mineral fertilizers has a higher content of all nutritional values - with the exception of iron, zinc, copper and molybdenum. All, however, remained within optimal values with the exception of calcium, magnesium, zinc and boron which were in excess while they were poor in iron and manganese.