【Objective】 To explore the effects of ridge furrow rainwater harvesting (RFRH) with biochar applica- tion on the number of root buds of alfalfa and cultivation techniques for high - yield of alfalfa in semi - arid region.【Method】 A randomized block design was designed to investigate effects of different biochar rates 0 ×104 (ridges compacted with soil),3×104 (ridges compacted with soil mixed with single biochar application),and 6×104 kg/hm2 (ridges compacted with soil mixed with double biochar application)) and different ridge widths (30,45,and 60 cm) on soil moisture,temperature,root buds,branch number,fodder yield,and water use efficiency(WUE) of alfalfa in RFRH,and flat planting (FP) was used as a control. The treatments were flat planting (FP),30/45/60 cm wide ridges compacted with soil (MCS30,MCS45,MCS60),30/45/60 cm wide ridges compacted with soil mixed with single biochar application (SMSBA30,SMSBA45,SMSBA60),30/45/60 cm wide ridges compacted with soil mixed with double biochar application (DMSBA3,DMSBA45,DMSBA60).【Result】 The number of stem buds of alfalfa was 2. 2~2. 9 times greater than that of root neck buds. The topsoil temperature at ridge top was affected by the ridges compacted with soil-biochar crust,but not at the topsoil temperature at the bottom of the furrow. With biochar appli- cation ridge-furrow rainwater harvesting increased soil water storage,the number of root buds (stem buds + root neck buds),branch number,fodder yield,and WUE of alfalfa. With the increase of ridge width,soil water storage, branch number and root buds increased,while fodder yield and WUE decreased. Compared with FP,soil water stor- age increased by 20. 7,30. 8,41. 7,8. 7,23. 0,35. 7,6. 2,12. 0 and 11. 0 mm,for MCS30,MCS45,MCS60,SMSBA30, SMSBA45,SMSBA60,DMSBA30,DMSBA45,and DMSBA60 respectively. Root buds increased by -0. 4,0. 4,2. 0, 1. 2,0. 7,4. 1,0. 4,3. 0 and 4. 6 per plant for MCS30,MCS45,MCS60,SMSBA30,SMSBA45,SMSBA60,DMSBA30, DMSBA45,and DMSBA60,respectively. Branch number increased by 28,50,48,84,109,45,91 and 71 per square meter for MCS30,MCS45,MCS60,SMSBA30,SMSBA45,SMSBA60,DMSBA30,DMSBA45,and DMSBA60,respec- tively;while fodder yield increased by 3. 34%,-0. 52%,-0. 70%,26. 81%,17. 11%,3. 00%,18. 28%,5. 79% and -11. 03%. For the same treatments,the WUE increased by -1. 76,-0. 04,2. 67,5. 77,4. 26,2. 99,4. 66, 1. 62 and 0. 10 kg/(hm2 ·mm),respectively.【Conclusion】 Optimum ridge width was 30 cm,and biochar application rate was 3×104 kg/hm2 for ridge-furrow rainwater harvesting with biochar application in semiarid regions of China.