Use of stabilized and dried sewage sludge in roll-on grass production

In the study, the possibilities and effects of dried and stabilized sewage sludge alone or together with chemical fertilizer applications were investigated. While evaluating the subject, it is also aimed to monitor the changes caused by the applications in the soil and plants by considering the heavy metal limit values specified in the regulation on the use of domestic and urban sewage sludge in the soil. In this context, hybrid bermuda grass (Cynodon dactylon x C. transvaalensis) "Tifway" and lolium grass (Lolium perenne L.) were grown together and harvested from the field as roll-on grass by performing chemical fertilizer application (KG+) and not performing chemical fertilizer (KG) application (KGØ) in the parcels where sewage sludge (AÇ) application is performed in increasing doses of 0 (AÇ0), 2 (AÇ2), 4 (AÇ4), 6 (AÇ6), 8 (AÇ8) ton da-1. The experiment was carried out in a soil with high pH (7.45) and lime (CaCO3) (46%) content on Akdeniz University Research and Application Farm land in 4 repetitions according to the randomized parcels experimental design. Within the scope of the study, observations and measurements were made in the field conditions, and also chemical analyzes were carried out on soil and plant (upper part-root) samples taken at the scheduled times. While a decrease in pH of the growing environments was observed in line with the applications, significant increases in electrical conductivity (EC), organic matter, total nitrogen, available phosphorus, total phosphorus, exchangeable potassium (K), magnesium (Mg), and sodium (Na) concentrations were also detected. The increase in the concentrations of available iron (Fe), manganese (Mn), copper (Cu) and zinc (Zn) in the growing environments, especially with sewage sludge applications, is remarkable. It was observed that the total Zn concentration increased with sewage sludge applications. There are issues where applications cause change, albeit very limited, on heavy metal contents of growing environments. However, no risky situation caused by applications was found in the study. On the other hand, considering the changes in cadmium (Cd) limit value in the regulation, it is thought that it will be useful to follow the change in the concentration of cadmium (Cd) element in repetitive applications. With the applications, while significant increases in nitrogen (N), potassium (K) and magnesium (M) concentrations of the plant upper parts were observed, change in Na concentration stayed more limited. A decrease was observed in calcium (Ca) concentration along with the applications. Another important change detected in the plant upper parts is related to the elements of Fe, Zn and Cu. As in growing environments, compatible increases with the applications in these three elements were detected in the upper part of the plant as well. However, it was determined that the sewage sludge applied in increasing doses decreased the Mn content of the plant upper parts compared to the control. While the effects of applications on the heavy metal content of plant tissues were found to be statistically insignificant for some elements, it was observed in some samples that they had a reducing effect on the concentration of the element in question. This effect was evaluated as far from creating risks and at negligible level since it was very limited in these elements in which an increase was recorded in their concentration along with the applications. Bioaccumulation factor (BAF) and translocation factors (TF) were calculated using the values obtained in the research. Within the calculated BAF, values greater than one were encountered in the plant upper part Zn, Cd and root Zn coefficients. For zinc, this value appears to remain at negligible level. However, values greater than one are quite a few within Cd BAF coefficients calculated for the plant upper parts. Some Cd BAF values were determined to be greater than 7. This has showed that at least one of the grass types that generate roll-on grass can be an accumulator plant for Cd. When the translocation factors were examined, it was determined that TF> 1 was for Zn, Mn, Ni and Cr elements. TF was found to be <1 for Fe, whose deficiency is frequently seen in the plant. This situation suggested that there was a problem in the transmission of Fe from the root to the upper parts as well as the uptake of Fe by the plant. When the translocation factor is analyzed for Mn and Ni, it is clear that the coefficient values determined in the second sampling period are lower, although no significant effect is observed along with the applications. In the study, in order to better evaluate the effects of the applications on roll grass, the data such as growth velocity of the plant, coating velocity, decomposition tolerance resistance, wet weight, dry weight, height, color and chlorophyll content were also collected and evaluated. In AÇ8KGØ application, which is the highest dose of sewage sludge applied alone, stolon growth was 17.75 days and the closure time of the parcel with grass was 27.5 days earlier than AÇ0KG+ application, where only chemical fertilizer was used. In addition, the tolerance resistance of the AÇ8KGØ application to decomposition was detected to be 58% higher than the AÇ0KG+ application. Significant increase has been achieved in the amount of green and dry grass removed by harvesting from the land with sewage sludge applications. With the similar applications, longer plant height was recorded and a positive change in the color of the grass was detected. It has been determined that chlorophyll content, which has a significant effect on both the color of the plant and its nutrition in relation to photosynthesis, has also increased with applications. In the study, results supporting the use of sewage sludge in the production of roll-on grass were obtained. Positive effects of sewage sludge applications on grass development and quality were determined. Observations showed that the improvement provided continued after laying roll-on grass. Some imbalances were observed in the development of the plants in parcels to which high doses of sewage sludge were applied. One of the clearest examples of this situation is the fact that the plant development progresses a little faster in the parcels applied with AC6 and AC8 dose sewage sludge. This situation made it difficult to manage the land especially in the early periods. Due to the fact that the plants in these parcels formed more frequently, labor and maintenance costs increased. Moreover, excessive use of the material has the risk of causing nitrate and heavy metal contamination in the long term. In order to use the material more effectively and safely, it was thought that it would be more beneficial to give the sewage sludge in two parts. The recommended application may be to apply 4 ton da -1 sewage sludge at the installation stage of the area, and 2 ton da -1 sewage sludge to the land after the first roll-on grass cutting. Also, in the study, it was observed that chemical fertilizer applications had some positive effects on AÇ0 and AÇ2 dose sewage sludge issues, but the effect of increasing sewage sludge doses and chemical fertilizer applications gradually became less important. This situation has suggested that it may be more beneficial to follow the potential deficiency symptoms in the land such as potassium, calcium and manganese along with the sewage sludge applications and fertilize these elements from the leaves if needed.