Abstract: 【Objective】 To determine the optimal water and nitrogen ratio for mixed sowing of the leguminous green manure crop Vicia villosa and Avena sativa in field cultivation. 【Methods】 A randomized block design was adopted. Three irrigation levels （450,600,750 m³/hm²） were established,and three nitrogen application levels （0,45,90 kg/hm²） were set for each irrigation level,resulting in a total of nine water and nitrogen ratio treatments. The yield and quality of the mixed crops,and soil moisture,changes in physicochemical properties,and water and nitrogen use efficiency in the 0-100 cm soil layer under different water and nitrogen ratios were monitored. 【Results】 With the increase in soil layer depth,soil water storage amount first increased and then decreased,and the maximum value tended to shift to deeper soil layers with the increase in irrigation amount. During the growth period of mixed sowing of V. villosa and A. sativa,the maximum water consumption amount occurred in the 20-40 cm soil layer. The fresh forage yield and dry forage yield of the SF6 treatment （600 m³/hm² water+90 kg/hm² nitrogen） were the highest,with values of 42 965.00 and 14 990.00 kg/hm²,respectively;the water use efficiency （52.43%） was significantly higher than that of other treatments （P<0.05）. There was no significant difference in nitrogen agronomic efficiency among different treatments （P>0.05）,but the nitrogen agronomic efficiency of the low nitrogen application treatments （SF2,SF5,SF8;average 36.33 kg/kg） was higher than that of the high nitrogen application treatments （SF3,SF6,SF9;average 22.67 kg/kg）. Compared with other treatments,the crude fat and crude protein contents of the mixed crops under the SF6 treatment were higher （4.96% and 15.45%,respectively）,while the neutral detergent fiber and crude ash contents were lower （55.76% and 7.39%,respectively）. 【Conclusion】 An irrigation amount of 600 m³/hm² and a nitrogen application amount of 90 kg/hm² are the optimal water and nitrogen ratio for mixed sowing of V. villosa and A. sativa. Under this condition,soil nutrient content,crop yield,and water use efficiency are improved,which is more favorable to increasing crude fat and crude protein contents and reducing neutral detergent fiber and crude ash contents of the mixed crops.

Key words: Vicia villosa, Avena sativa, Mixed sowing, Water and nitrogen ratio, Water and nitrogen use efficiency, Yield, Quality