Effect Of Biosolids On Kentucky Bluegrass(Poa Pratensis L.)Drought Stress

To study effect of biosolids on Kentucky bluegrass (Poa pratensis L.) drought resistance mechanisms, the greenhouse study investigated impact of biosolids on growth and metabolic activities in drought-stressed Kentucky bluegrass. Treatments included a fertilizer control, indole-3-butyric acid (IBA) at2μM (hormone control), biosolids. Two experiments were conducted, one in which no soil moisture stress was imposed(well-watered regime) and one in which soil moisture was limiting, and two wilting and recovery cycles were imposed (moisture stress regime). Each experiment was arranged as a completely randomized design. Another greenhouse study investigated effect of biosolids on bluegrass drought resistance mechanisms. Treaments included a fertilizer control, biosolids (35.5g pot-1) and1/2biosolids (17.75g pot-1) both on well-watered regime and on drought and rewatering regime. The results showed as followed:1. Biosolids application can improve turfgrass quality and growth both after bluegrass mature and before seeding under well watered regime.2. Biosolids treatment improved turfgrass quality and leaf water status under moisture stess and rewater recycle and delayed leaf wilting during drought period. During drought and rewater period, biosolids treatment had significantly difference in MDA content relative to the control on three of four sampling dates except13Aug. On24Sep., rate of Kentucky bluegrass MDA content increasement due to biosolids application was lower17%than that due to the control. The data suggest that biosolids application may impove plant drought resistance.3. Under moisture stress and rewater recycle regime, leaf IAA content decreased of the control in response to drought during the second drought maximum. Leaf IAA content increased due to biosolids treatment on all five sampling dates. Biosolids treatment increased leaf IAA by38%and 100%, respectively, during each of two maximum drought periods. The results show that biosolids application may alter growth hormone (IAA) content and improve plant drought resistance.4. Biosolids and1/2biosolids treatment improved root mass by63.5%and34.5%, respectively, relative to the control under well watered regime.1/2biosolids treatment promoted root growth to enhance root mass by53.1%than that of the control under moisture stress and rewater regime. The results of this study indicate that grasses with greater root systems due to biosolids application may have better leaf water status, reducing leaf wilting during drought stress. Larger, active root systems may have greater capacity for producing growth hormones such as IAA.5. The results of this study also indicate that biosolids treatment enhanced leaf SOD activity under drought stress. Greater SOD activity may be more effective in suppressing ROS toxicity, thus protecting cell functions under drought stress. POD and APX activity after rewatering7d recovered higher level than that before moisture stress, which means POD and APX activity may relate with removing H2O2and repairing cell membrane during rewatering period.