Reuse of wastewater and sludge utilization on Pinus pinea L. and Pinus halepensis Mill

The present paper reports on the experimental results of wastewater and sludge application in irrigation and fertilization of forest species grown under greenhouse conditions. The sludge was taken from Agrinio W.W.T.P. A randomized block design was used which included 5 treatment combinations composed of a) control (irrigation water only), b) wastewater (WW), c) sludge and wastewater, d) sludge and irrigation water, and e) diluted sludge (20%) and wastewater, in two replications and two forest species i.e. Pinus pinea L. and Pinus halepensis Mill.. Each experimental plot included 10 plants, grown in plastic bags, with a total of 5x2x2x10 =200 plants. Soil and plant samples were analyzed, and the following was found: The combination of "WW and sludge" treatment increased the mortality of Pinus pinea L. due to low availability of Fe, attributed to the fixation of this element, in the alkaline environment of the sludge (pH 7.5). On the other hand, plain sludge improved plant growth. Similarly, sludge and WW (pH 7.45) increased the mortality of Pinus halepensis Mill, while application of sludge alone affected favorably plant growth. The distribution of macro- and microelements between soil and plants was found to vary, depending on the kind of the element and the plant species. As a general trend, the macro- and micronutrient content of each forest species studied was correlated to its respective accumulation in the soil. The interrelationships between the macro and micro-nutrients, however, were found to be dependent on: a) the extent of the element's accumulation in the soil, b) the physical and chemical characteristics of the soil, c) the intensity of the interacting elements, and d) the genotypical characteristics of the forest species. Manganese (Mn) was accumulated mainly in the soil as well as in the roots, with only a small fraction of it being concentrated in the leaves. Most likely, the adverse conditions (high pH) prevailing in the soil, and the observed Mn versus Fe antagonism, may have contributed to Fe-chlorosis of plants, observed during the early stages of growth.