Eiosolids Impact On Nitrogen Metabolism And Root Growth Of Kentucky Bluegrass (Poa Pratensis L)

Biosolids have nutrient and biostimulant values and will impact turfgrass growth, and drought resistance. On the premise of eliminate the effects of nutrients from biosolids on results, this greenhouse study was studied on the effects of application of biosolids on nitrate reductase activity, proline and amino acid content, endogenous hormone content, turfgrass quality as well as root growth indicators of Kentucky bluegrass(Poa pratensis L.) under both water regimes, identified the effects of biologically active substances of biosolids on nitrogen (N) metabolism and root growth as well as drought resistance of Kentucky bluegrass. The results indicated that:(1) Application of biosolids significantly increased nitrate reductase activity of Kentucky bluegrass compared with control under both water regimes, especially under drought stress; in addition, biosolids also increased proline and total free amino acid content of Kentucky bluegrass compared with control under drought stress. Those results indicated that biologically active substances of biosolids can promote nitrogen metabolism, as well as drought resistance of Kentucky bluegrass.(2) Application of biosolids significantly increased root growth indicators of Kentucky bluegrass compared with control under well-watered conditions. However, there was no significant difference in root weight between biosolids and control under drought stress, but biosolids1x rate improved root length density by17%and23%, respectively, compared with biosolids0.5x rate and control; what’s more, biosolids1x rate also promoted root surface area by20%and31%, respectively, compared with biosolids0.5x rate and control. So this greenhouse study indicated that biologically active substances of biosolids can promote root growth of Kentucky bluegrass from a new perspective.(3) Application of biosolids significantly increased auxin (lAA) content of Kentucky bluegrass compared with control under both water regimes. This may be because biologically active substances of biosolids provided plant growth regulators directly or stimulated the activity of microbes to provide plant growth regulators indirectly, thereby improved endogenous IAA content of Kentucky bluegrass; the abscisic acid (ABA) content of control was24%and17%higher than biosolids Ix rate and biosolids0.5x rate at the end of drought stress. This indicated that application of biosolids also significantly reduced abscisic acid (ABA) content compared with control under drought stress, thus can delay leaf stomatal closing, improve air exchange, and alleviate plant oxidative stress, as well as promote drought resisitance of Kentucky bluegrass.(4) Application of biosolids significantly increased turfgrass quality and leaf relative water content, in addition, application of biosolids also reduced leaf wilting, this indicated that biologically active substances of biosolids can delay the senescence of leaves as well as maintained leaf turgor pressure of Kentucky bluegrass.In conclusion, biologically active substances of biosolids can promote nitrogen metabolism and root growth, as well as regulate the balance of endogenous hormone, improve drought resistance of Kentucky bluegrass.