Effect Of Sowing Time On Alfalfa Productivity And Overwintering Characteristics In Horqin Sandy Land

In order to determine the suitable sowing date of Alfalfa in Horqin sandy land,three alfalfa varieties,Knight T,Gongnong No.1 and Optimus Prime,were selected from the grassland core area of Arukherqin Banner,Inner Mongolia,from 2017 to2018.They were sown on July 1 and sowed every five days for a total of 10 sowing dates.The effects of sowing date on the growth and Physiological changes of Alfalfa before winter,the rate of returning to green and the Production Performance of Alfalfa in the following year were studied.The results show that:The later the alfalfa was sown,the lower the hay yield was,Knight T hay yield decreased significantly on 21 July(P < 0.05),Gongnong 1 hay yield decreased significantly on 16 July(P < 0.05),and OPtimus Prime hay yield decreased significantly on 11 July(P < 0.05).The Plant height,single branch weight,stem-leaf ratio and root neck diameter of Alfalfa decreased with the PostPonement of sowing date.With the PostPonement of sowing date,the number of Knight T increased first and then decreased.The number of Gongnong 1 and OPtimus Prime increased gradually,and the number of branches of three alfalfa varieties increased first and then decreased.The number of Plants of Gongnong 1 was more than that of Knight T and OPtimus Prime,and the diameter of root neck of Knight T was larger than that of Gongnong 1 and OPtimus Prime.With the delay of sowing date,soluble sugar and soluble Protein in alfalfa root neck gradually decreased,MDA content gradually increased,soluble Protein,soluble sugar,free amino acid,POD activity and overwintering rate were significantly Positively correlated,SOD activity and overwintering rate were Positively correlated.The Overwintering Rate of Alfalfa began to decrease significantly on July 16,and the rejuvenation rate of Gongnong No.1 sown before July 16 was significantly higher than that of Knight T and OPtimus Prime(P < 0.05),but there was no significant difference in the rejuvenation rate of three alfalfa varieties after July 16(P< 0.05).The total hay yield of Alfalfa in the following year showed no significant difference among the three varieties;the hay yield of Alfalfa decreased gradually with the PostPonement of sowing date;the hay yield of Alfalfa in the first croP decreased significantly from 21 July,while that of Alfalfa in the second croP did not change significantly;comPared with the three varieties,the hay yield of Gongnong 1 in the first croP was significantly higher than that of Knight T and OPtimus Prime,and thehay yield of Alfalfa in the second croP was significantly higher than that of Knight T and OPtimus Prime.There was no significant difference in sPecies.Gongnong No.1in the third croP was significantly lower than Knight T and OPtimus Prime.The Plant height of one stubble of Alfalfa decreased gradually with the delay of sowing date,but there was no difference between two and three stubbles.The number of alfalfa Plants and branches decreased with the delay of sowing date.With the increase of cutting times,the number of alfalfa Plants decreased gradually.There was no difference in the number of two or three stubbles.It is suggested that the optimum period for planting alfalfa in Horqin sandy land should be after July 1 and before July 16,not later than July 21.