Influence of Black Charcoal Application on Fruit Yield and Chemical Properties of the Soil in High Density Apple Orchards

In fruit growing, an important problem is the process of the annual supply with chemical fertilizers, which overestimated may lead to water and soil pollution. Before 1990's the manure use every 3-4 years, at a rate of 40-50 t/ha, especially on heavy soils, was a method for nitrogen fixation and its progressive release to plants. By application of black charcoal into the orchard soil, we aimed to ensure nitrogen fixation and its progressive release to the plants, as a replacement for manure use. The researches regarding application of the black charcoal were conducted at the Research Institute for Fruit Growing Pitesti Romania, in a 5 years old high density apple orchard. The experience type is a bifactorial one, 2 x 4: A factor - the application depth with the graduations a1 - 0-0.2 m; a2 - 0-0.4 m; B factor the charcoal dose: with the graduations b1 - untreated control treatment - without black charcoal use, b2 - black charcoal 1 kg m(-2); b3 - black charcoal 5 kg m(-2) and b4 - black charcoal 10 kg m(-2). In the third year after the black charcoal application, the fruits yield increase ranged between 11.0 - 49.7% depending on the dose of charcoal compared to the untreated control. An increase in total nitrogen content of the soil was registered two years after black charcoal application compared with untreated control and according to the rate and incorporation depth. The phenomenon should be explained by the fact that the organic nitrogen was adsorbed inside and on charcoal particles and after three years the phenomena of desorbtion began, and the accumulated nitrogen was released to the plants.