Abstract: On the Haihe plain, the traditional 3-5 cutting of alfalfa are difficult to achieve in wet growing seasons. To explore this problem, two field experiments were conducted from 2011 to 2016 to analyze the production performance and economic benefit of interplanting alfalfa with various forage crops in summer. Five different forage crops were evaluated: silage maize, Sorghum bicolor×Sorghum sudanense, Dolichos lablab, fodder soybean, and forage millet. The results indicated that there were no significant differences between 30-30 cm and 20-40 cm row spacing treatments (P>0.05). The hay yield of the first two cuts of alfalfa for the second year when alfalfa was interplanted with S. bicolor×S. sudanense was significantly lower than for alfalfa alone (P<0.05). The total feed equivalent units when interplanting silage maize with alfalfa were significantly higher than for alfalfa alone (P<0.05); but the total economic benefits were not significantly different (P>0.05). The average solar energy use efficiency, water use efficiency, and land equivalent ratio when interplanting silage maize and alfalfa in summer were significantly higher than for alfalfa alone (P<0.05. Other research into the yield performance for alfalfa interplanted with silage corn showed that there were no significant differences (P>0.05) in the first two cuts between 30-30 cm and 20-40 cm row spacing treatments for hay yield, total feed equivalent units, total economic benefit, average solar energy use efficiency, water use efficiency, land equivalent ratio. Considering all the results, the optimal planting details for alfalfa interplanted with silage maize are as follows: the alfalfa field is planted in autumn using alternate wide and narrow row spaces of 20 and 40 cm. The silage corn is interplanted in the wide row space after the second cut of alfalfa is harvested in second year. The plant density of silage maize was less than 60000 plants·ha^-1 and the maize is harvested with alfalfa at the end of September, after which the alfalfa overwinters normally. The following year silage maize is replanted as the above. The interplanting methodology developed in this study is more easily implemented than the traditional 3-5 cuts of alfalfa in wet growing seasons and enhances solar, water and land resource use efficiency with the promise of corresponding economic benefits.

Key words: alfalfa, interplanting, forage crop, production performance, benefit evaluation