Productivity Evaluation Of Vicia Sativa In Different Cropping Systems At Lhasa Area Of Tibet,china

The alpine steppe of the Tibetan Plateau is the main base of grassland livestock production and ecological barrier.Forage deficiency in the cold season is one of the most important limiting factors in livestock production.This study used the series common vetch(Vicia sativa)varieties cultivated by College of Pastoral Agriculture Science and Technology of Lanzhou University as test crops to evaluate the productivity at sole sowing and rotation systems with a two year field experiment during 2016-2017.The purpose of the study was to provide support for establishing efficient grassland agricultural system.The main obtained results were as follow:1.The highest hay biomass at full folowering stage in sole sowing treatment was 5.66t/hm2 observed at Lanjian no.1.Similar values were witnessed at 333/A and Lanjian no.2,were 4.94 and 4.90 t/hm2,respectively,the lowest value appeared at Lanjian no.3,was 4.47t/hm2.In terms of dry matter accumulative rate,the highest value still recored at Lanjian no.1,was 6.7 g/d,333/A,Lanjian no.2 and Lanjian no.3 were 5.9,5.8 and 5.2 g/d,respectively.Lanjian no.3 produced the highest seed biomass,was 2.43 t/hm2,followd by 333/A,Lanjian no.2 and Lanjian no.1,were 2.23,1.97 and 1.67 t/hm2.At full flowering stage,no significant difference was witnessed at crude protein biomass of 333/A,Lanjian no.1 and Lanjian no.2,were 21.71%,21.45% and 21.13%,respectively,however,crude protein biomass of the three varieties was significantly higher than Lanjian no.3(P<0.05),was 19.10%.The results of crude protein biomass accumulative rate was in accord with that of crude protein biomass.2.Among the five test rotation systems,the highest yield was observed at Lanjian no.1-winter barley(Hordeum vulgare)-rape(Brassica campestris)(V-H-R)and rape-winter barley-rape(R-H-R),were 27.24 and 26.89 t/hm2.Followed by Lanjian no.1-winter barley-Lanjian no.1(V-H-V)and rape-Lanjian no.1-rape(R-V-R),were 24.40 and 17.52 t/hm2.Local traditionl system fallow-winter barley-fallow(F-H-F)produced the least yield,was only 12.58 t/hm2.Crude protein biomass was significantly different among the five rotation systems.R-H-R still the highest at crude protein biomass,was 3.68 t/hm2,followed by R-V-R,V-H-R,V-H-V and F-H-F,were 3.33,3.50,2.13 and 0.78 t/hm2.3.Among the five rotation systems,soil total nitrogen content at 0-30 cm was significantly increased compared to sowing.Rotation systems with Lanjian no.1 like V-H-V and V-H-R improved by 134.9%,19.6% and 115.6%,9.8%,respectively.Compared to sowing,soil organic carbon content showed an increasing trend,but no significant difference was observed among the five rotations systems.4.In terms of the economic production value,the highest value were appeared at V-H-V andV-H-R,were 44284 and 41444 yuan/hm2,respectively.Followed by R-H-R,R-V-R and F-H-F,were 36330,29243 and 17674 yuan/hm2,respectively.The test three Lanjian series common vetch varieties showed a good productivity in Lhasa region,soil fertility was siginificantly improved after harvest(P<0.05).The rotation systems with Lanjian no.1 like V-H-V,V-H-R and R-V-R displayed a higher productivity than traditional F-H-F.Compared to R-H-R rotation system,V-H-R and V-H-V also performed better.Although R-V-R was lower in productivity,it avoided the detriment to soil caused by fertilizer and played a more important role in soil improvement.Consequenctly,the Lanjian series common vetch provide a valuable forage to allievate the shorage of forage in livestock production in the Tibetan Plateau region and have a great application potential.