DIGITALNA ARHIVA ŠUMARSKOG LISTA
prilagođeno pretraživanje po punom tekstu
|ŠUMARSKI LIST 11-12/2020 str. 32 <-- 32 --> PDF|
these mixtures increased seedling height in the rates of 25.1%, 22.4%, 20.2%, 19.8%, and 16.5%, respectively. The rate of sewage sludge in these mixtures varied between 25-100%, and the highest growths were observed in mixtures with 75%-100% sewage sludge.
In addition to seedling height, application of sewage sludge to growing media also affected the stem diameter of the seedlings significantly. The stem diameter of Scots pine seedlings varied between 0.56-1.07 mm. The highest stem diameters were observed in 1st, 3rd, and 9th mixtures. As compared with the control (14th mixture), these mixtures increased stem diameter in the rates of 7%, 7%, and 5%, respectively. As in seedling height, the highest stem diameters were observed in mixtures in which sewage sludge was applied.
Shoot and root dry weight measurements also demonstrated some differences in plant development during the experimental growth period. The shoot and root weight of Scots pine seedlings varied between 0.04-0.27 g and 0.05-0.27 g, respectively. For both of the measured parameters, the highest values were obtained from 1st, 9th, and 3rd mixtures. The rate of sewage sludge in these mixtures varied between 50-100%. The lowest values were obtained in mixtures were the diatomite was added in 75%.
The maximum values for Dickson Quality Index (QI) are desirable. The QI of Scots pine seedlings varied between 0.011-0.085. Among the substrates tested, sewage sludge added mixtures showed the best QI values. The highest QI values were observed in 3rd, 1st, and 9th mixtures. As compared with the control (14th mixture), these mixtures increased QI in the rates of 129.7%, 100%, and 78.4%, respectively. The effects of substrate mixture on QI showed the same tendency with other parameters investigated.
To evaluate the land performance of Scots pine seedlings grown in different substrates, a trial was established between the years 2013-2017 in Sarıkamış, Kars. Land performance of Scots pine seedlings (Pinus sylvestris L.) grown on different substrates are presented in Table 3. Survival rates and height and stem diameter of seedlings varied significantly. The survival rate of Scots pine seedlings varied between 65%-96%. The highest survival rates were observed in 3rd, 6th, 10th, 14th, 9th, and 4th mixtures. The highest plant height and stem diameters were observed in the 9th and 3rd mixtures, respectively. As compared with the control (14th mixture), the 9th mixture increased plant height and stem diameter in the rates of 11% and 12.4%, respectively. The composition of this substrate was 50%P+50%SS.
Results obtained have shown that even at low application rates (25% SS, 13th and 10th mixtures) sewage sludge increased seedling height significantly. The C:N ratio of organic matter is an important index that shows how much nitrogen will be mineralized relative to the CO2 released by microorganisms (Ge et al. 2013). Organic amendments with high N contents and low C:N ratios mineralize sufficient N to satisfy plant growth (Cordovil et al. 2005). The high rate of organic matter and C in sewage sludge is responsible for the increased growth of seedlings. Mineralization of sewage sludge may have led to a sufficiently fast release of nutrients to meet the seedling requirements. Epstein et al. (1978) have stated that anaerobically digested sludge gave N mineralization rates of 40-42% in 15 weeks. Sewage sludge application, due to its high organic matter and macro and micronutrient content, may have improved the composition of rhizosphere, thereby resulting in growth acceleration. Similar results were reported by Perez-Murcia et al. (2006) for broccoli, Tufekci et al. (2008) for Pinus brutia, Aslantas et al. (2013) for sour cherry, and Leila et al. (2017) for Eucalyptus camaldulensis.
The reason of increase in stem diameter can not only be related to high organic matter of sewage sludge and its N, P, and K content, but also to improved soil water holding capacity (Bramryd 2002; Angin and Yaganoglu 2009). Velayoudon et al. (2014) have stated that there is a linear relationship between plant growth and trunk diameter. Valdecantos et al. (2011) have shown that pines amended with liquid biosolids showed 6-11% increases in stem diameter