Effects Of Wate Management With Intervention On Growth And Morphology Of Kikuyu Grass In Compound Contaminated Soil

The soil near mining areas in southern China is often polluted by multiple elements.In summer,the continuous heavy rainfall causes the soil to be flooded to varying degrees,which will have a serious impact on the morphology and growth of plants.Biochar and organic fertilizer can increase soil nutrition,improve soil structure,and alleviate plant flooding stress.Nitrogen(N)and phosphorus(P)are essential elements in plant growth and morphological development.Applying N and P fertilizer can promote plant growth and alleviate the adverse effects of flooding on plant growth.Kikuyu grass(Pennisetum clandestinum hochst.ex Chiov.)is a rapidly growing grass,planted in southern China.In this study,pot experiments were conducted to explore the growth and morphological changes of kikuyu grass under different flooding conditions in As,Zn,Pb,Cd,and Cu compound contaminated soil,the effects of different water management conditions with organic fertilizer,biochar,and nitrogen and phosphorus fertilizer interventions on the growth and morphology of kikuyu grass,and providing a theoretical basis for the planting of kikuyu grass in the compound contaminated soil of rainy area in southern China.(1)Growth and morphological changes of kikuyu grass under different water conditionsThe experiment used a single-factor completely random design and set up eight different soil moisture treatments: CK(60 % field water holding capacity),drought(30 %field water holding capacity),intermittent flooding 5 cm,continuous flooding 5 cm,intermittent flooding 10 cm,continuous flooding 10 cm,intermittent flooding 15 cm,and continuous flooding 15 cm.The main research results are as follows: Kikuyu grass can adapt to a long-term continuous flooding environment.The plant height and biomass were increased,while the the number of leaves and the soil p H were significantly decreased in the flooding treatments.In addition,the decrease of soil p H in the continuous flooding treatment was greater than that in the intermittent flooding treatment.(2)Effects of water management conditions with organic fertilizer and biochar addition on growth and morphology of kikuyu grass in the compound contaminated soilThe experiment used a two-factor completely random design,and the experiment set two factors: water management and the addition of organic fertilizer and biochar.The water management conditions were set for two treatments: conventional water management(60%field water holding capacity)and intermittent flooding of 5 cm.The four treatments of interventions of organic fertilizer and biochar were no addition(-OF-BC),added organic fertilizer(2%OF),added biochar(2%BC)and added organic fertilizer with biochar(1%OF+1%BC).The main results were as follows: Compared with conventional water management,flooding treatment significantly reduced the number of tillers in-OF-BC treatment,while has no significant effect on 2%OF,2%BC and 1%OF+1%BC treatments.Compared with-OF-BC,2%OF treatment significantly increased biomass of kikuyu grass under both conventional water management conditions and intermittent flooding conditions.(3)Effects of water management conditions with nitrogen and phosphorus fertilizer application on growth and morphology of kikuyu grass in compound contaminated soilThe experiment used a two-factor completely random design,and the experiment set up two factors: water management and fertilizer application.Water management conditions were set for two treatments: conventional water management(60% field water holding capacity)and intermittent flooding 5 cm,The four treatments of nitrogen and phosphorus fertilizer application were no nitrogen and phosphorus fertilizer(0N+0P),nitrogen 100mg/kg(100N),phosphate 100 mg/kg(100P),nitrogen 100 mg/kg with phosphate 100mg/kg(100N +100P).The main results were as follows: Compared with conventional water management,intermittent flooding significantly reduced the number of tillers of kikuyu grass in 0N+0P treatment.100 N,100P and 100N+100P treatments all promoted tillering of kikuyu grass and relieved the intermittent flooding stress.Compared with 0N+0P treatment,the 100 N treatment significantly increased the above-ground biomass of kikuyu grass under conventional water management conditions,and significantly increased the plant high,above-ground biomass,total biomass,root dry weight and root volume of kikuyu grass under intermittent flooding conditions;100N+100P treatment significantly increased the above-ground biomass of kikuyu grass under conventional water management conditions;100P treatment had no significant effect on the growth of kikuyu grass.In summary,kikuyu grass can grow under continuous flooding for a long time,it adapts to flooding conditions by reducing the number of leaves and tillers.Adding organic fertilizer,biochar and applying nitrogen and phosphorus fertilizers can all promote the tillering of kikuyu grass under intermittent flooding conditions.The addition of organic fertilizer and application of nitrogen fertilizer can promote the growth of the upper part of kikuyu grass under both conventional water management and intermittent flooding conditions.The application of nitrogen fertilizer under intermittent flooding conditions can also increase the root dry weight and root volume of kikuyu grass.