Effects Of Soil And Light On Forage Seed Germination,Seedling Growth And Photosynthetic Characteristics In An Apple Orchard Of Eastern Gansu

As a new type of orchard management,inclusion of grasses in the orchard can reduce the exposed area of the soil surface and improve the efficiency of soil utilization,reducing soil erosion.The orchard grasses can also be used as green manure or mowed in the later stage of growth,which is beneficial to the orchard environment and animal husbandry development.The successful establishment of grassland is the basis of orchard-grass pattern,but it is readily affected by many factors,which restricts the application and promotion of orchard-grass pattern.The soil specificity of apple orchard may affect the germination of grass seeds and seedling growth,thus affecting the establishment of undergrowth grassland.In addition,shade of fruit trees and microclimate variation under the trees also affect the growth of orchard grass.1.The soil extracts did not affect seed germination rates of ryegrass(Lolium perenne L.)and lucerne(Medicago sativa L.),but inhibited the radicle growth of ryegrass and promoted the germ growth of ryegrass and lucerne.Compared with leafless soil,the extract from soils with leaves could accelerate the germination of forage seeds and increase the germination rate.2.The germination rate of ryegrass and lucerne seeds was decreased by root extract,and the germination rate of ryegrass seeds was promoted by leaf extract at low concentration,and the radicle growth of ryegrass and lucerne was promoted by root and leaf extracts.Leaf extract promoted the growth of germ and root extract inhibited the growth of germ.3.Compared with those outside of the orchard,the height,stem and leaf dry weight,and root volume of ryegrass in the orchard were greater,while there was no significant difference in root dry weight and root surface area.The leaf area,stem and leaf dry weight,root dry weight and root surface area of lucerne were lower in the orchard.4.The dark respiration rate,apparent quantum efficiency,light compensation point and maximum photosynthetic rate of cocksfoot(Dactylis glomerata L.)were higher underbranch-cutting than net-shading,while light saturation point was lower.The dark respiration rate,light compensation point,light saturation point of cocksfoot was lower than those of lucerne under all light treatments,while maximum photosynthetic rate was higher than that of lucerne under branch-cutting.The contents of chlorophyll a,b and a+b of cocksfoot were higher than those of lucerne under all light treatments,but chlorophyll a/b was lower than that of lucerne.In summary,the soil of apple orchard affected the establishment of grassland by inhibiting seedling growth of grasses rather than seed germination.Lucerne was not suitable for establishing the grassland in the apple orchard in rainfed region of eastern Gansu,China.Some shading-tolerant plants are more suitable for planting in the orchard,for instance,cocksfoot.Orchard-grass pattern can be used,combining with fruit tree management,such as branch-cutting or low density planting.