J. M. Gascó

USE OF PINE BARK AND SEWAGE SLUDGE COMPOST AS COMPONENTS OF SUBSTRATES FOR PINUS PINEA AND CUPRESSUS ARIZONICA PRODUCTION

The feasibility of using pine bark and composted sewage sludge to produce alternative substrates was studied. The substrates tested were 1 and 2) pine bark fertilized with 1 and 4 g L−1 of a slow-release NPK fertilizer (15 : 11 : 13) and 3) a substrate in which 15% (v/v) of the pine bark was replaced by composted sewage sludge. Treatments abbreviated as PB, PB + N, and PB + CSS in text. Pinus pinea and Cupressus arizonica plants were grown in these substrates for 2 years and plant and substrate characteristics were tested periodically along the experiment. Additionally, nitrate and heavy metal concentrations were determined in leachates collected from each substrate. The suitability of the prepared substrates was appropriate for the production of Pinus pinea and Cupressus arizonica in real production conditions. The root/shoot dry weight ratio of both plant species in PB + N was significantly lower than in the other substrates. The highest nitrogen content in shoot corresponded to plants grown in the PB + N substrate, even though PB + CSS had higher nitrogen content than PB and PB + N substrates. Concentration of nitrate and heavy metals in leachates was lower than the level allowed in the European Union regulation.

Initial organic matter transformation of soil amended with composted sewage sludge

Abstract An incubation experiment with composted sewage sludge (CSS) just added to the soil was conducted to determine its initial effects on C decomposition, N nitrification and the transformation of organic matter. CSS was mixed with a sandy loam soil from uncultivated ochric epipedon of a Typic Haploxeralf at rates of 0, 40 and 80 t ha–1 (dry weight). The data obtained showed that with regard to the unamended soil, both the 40 and the 80 t ha–1 treatments produced the same result in decreasing respiratory activity, but the addition of increasing amounts of CSS progressively delayed C decomposition. The nitrification index (NI), defined as the relation between nitrate-N and nitrate-N + ammonium-N, increased in correlation with the C mineralization coefficient. Total organic matter decreased after incubation whereas the humic substances increased in relation to the total C mineralized.

Integrated evaluation of soil quality after the incorporation of organic matter and microorganisms

The soil quality was evaluated following the addition of organic matter and microorganisms to a clay loam soil collected in Aranjuez (Madrid) under controlled conditions of temperature and moisture, and over a period of three months. The following treatments were carried out: soil (control); soil + 50 t/ha of animal manure (E50); soil + 50 t/ha of animal manure + 30l/ha of effective microorganisms (E50EM); soil + 30 t/ha of combination of various green crop residues and weeds (RC30) and soil + 30 t/ha of combination of various green crop residues and weeds + 30l/ha of effective microorganisms (RC30EM). The soil samples were taken before and after the incubation and analysed using physical, chemical and microbiological parameters. A significant increase in the production of polysaccharides and alkaline phosphatase and esterase enzymes in the treatments E50EM and RC30EM was observed, being in direct correlation with the humification of the organic matter, with the water retention at field capacity, and with the cationic exchange capacity (CEC). It can be concluded that the incorporation of microorganisms EM potentialized the soil biological activity and improved physico-chemical soil properties, contributing to a quick humification of fresh organic matter. Those findings were proved by microbiological activities of exopolysaccharides by alcaline phosphatase and esterase enzymes, which can be used as earlier and integral soil health indicators.