| Lespedeza potaninii Vass is an excellent leguminous forage that plays an important role in forage production and grassland improvement.L.potaninii Vass cv.Tenggeli is a new domesticated variety by Lanzhou University（No.GS-CWV-2020-007）,which has drought resistance,cold resistance and infertile tolerance,and is adapted to growth at arid and semi-arid areas in northern China with annual rainfall of 100-400 mm and the Loess Plateau.It is an excellent legume forage for desert grasslands replanting,vegetation restoration in arid areas and establishing artificial grasslands.As a result,the demand for its seed is gradually increasing.However,there are problems such as low seed yield,difficulty in threshing and the hard seed rate is very high in L.potaninii Vass;in addition,the effect of its mixing with Cleistogenes songorica has not information.Therefore,this study investigates the seed production,removal of persistent sepals and hard seed breaking techniques of L.potaninii Vass;it also explores the effect of its mixed sowing with C.songorica.The main results were as follows.1.The effects of plant density and phosphorus fertilizer on the seed yield of L.potaninii Vass cv.Tenggeli was studied in Zhangye,Gansu,from 2020 to 2021.The plant density treatment(33,333,44,444,66,666 and 133,333 plants ha-1,the corresponding within-row and between-row spacing was 60×50,45×50,30×50 and15×50 cm,respectively.),phosphorus fertilizer treatment(0,45,90,135 and 180 kg ha-1)and their interaction significantly affected the seed yield of L.potaninii Vass（P<0.01）.At the plant density of 44,444 plants ha-1 and phosphate fertilizer rate of 90 kg ha-1,the average seed yield over two years reached a maximum of 477.5 kg ha-1.Among yield components,pods per raceme and florets per raceme were significantly and positively correlated with seed yield（P<0.05）.Therefore,the plant density of 44,444 plants ha-1（within-row spacing:45 cm,between-row spacing:50 cm）and phosphorus fertilizer rate of 90 kg ha-1 are recommended as the best agronomic practices for seed production of L.potaninii Vass cv.Tenggeli.Further research was conducted on seed threshing and hard seed breaking techniques for L.potaninii Vass.The seed coat breaking machine can completely remove the persistent sepals by treating 4 times;treating 9 times can effectively reduce the seed hardness rate,the germination rate can reach greater than60%,and the operation is convenient and safe,thus can be recommended in the large-scale seed production.2.The effect of mixed sowing of L.potaninii Vass cv.Tenggeli and C.songorica cv.Tenggeli was investigated in Qingyang,Gansu,from 2020 to 2021.In the second year of establishment,the highest plant height was recorded for L.potaninii Vass and C.songorica with the 1:2 mixture（L1C2）,and the biomass and coverage were the highest in the mixture treatments except for monoculture of C.songorica.The relative densities（DR）of the two species in different mixed sowing treatments were greater than 1,indicating that both legume and grass specie expanded their populations after mixed sowing,but the relative density of C.songorica kept decreasing with time,indicating that to a certain extent,L.potaninii Vass suppressed the tillering of C.songorica.The competition rate of L.potaninii Vass was greater than 1 in different mixed sowing treatments,indicating that the competitiveness of L.potaninii Vass（CRL）was greater than that of C.songorica,and the competitiveness of L.potaninii Vass gradually increased with time,but the competitiveness of the two forages was similar when L.potaninii Vass and C.songorica were mixed 1:2（L1C2）.Meanwhile,the relative yield total（RYT）of all the mixed treatments was greater than 1,among which the 1:2 mixture（L1C2）of L.potaninii Vass and C.songorica was the largest,indicating that in the second year of establishment,the ecological niches of the two forage grasses in all mixed treatments were differentiated and could make full use of resources,showing a symbiotic relationship. |
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