Effects of irrigation on mixed sowing of leguminous and graminaceous forages

Yield performance and inter-specific competitive relationship for single sowing by two leguminous forages (Medicago sativa and Astragalus adsurgens) and three graminaceous forages (Aromus inermis, Elymus dahuricus and Agropyron cristatum) and mixed sowing between the two families forages were studied under three water conditions in Ningxia Central Semi-arid Belt. The two-year results showed that the yield for the combination between M. sativa and graminaceous forages was slightly lower in medium water condition (T2) and higher in the least water supply treatment (T1) and well watered conditions (T3) than single sowing yield of M. sativa. The yield for the combination between A. adsurgens and graminaceous forages was higher than that of single sowing of A. adsurgens. The single sowing yield of M. sativa was higher in 2011 and under well watered conditions (T3) for the first and second harvestings in 2012 and lower under the least water supply treatment (T1) in 2012 compared with that of A. adsurgens. The mixed sowing yield of M. sativa was less than its single sowing yield in 2011 and under T3 water condition in 2012 but higher than its single sowing yield under T1 condition in 2012. The mixed sowing yield of A. adsurgens was higher than its single yield in 2011 and 2012. The single sowing yield of M. sativa was higher in 2011 and under T3 water condition in 2012 and lower significantly under T1 in 2012 than that of A. adsurgens. The mixed sowing yield of M. sativa was less than its single yield in 2011 and under T2 and T3 for the first harvesting and higher under T1 in 2012. The mixed sowing yield of A. adsurgens was higher than its single sowing yield under T2 and T3 in 2012 for the second harvesting. For the third harvesting in 2012, the mixed sowing yield of A. adsurgens was lower under T3 and higher under T2 and T3 than its single sowing yield in 2012. When being sown with graminaceous forages, M. sativa dominated over the graminaceous forages. To the contrary, the proportion, CR (competitive rate) and plant height of graminaceous forages in mixed sowing combinations between A. adsurgens and graminaceous forages tended to be stable. Moreover, the combinations with RYT1 for the mixed sowing between A. adsurgens and graminaceous forages were more than those between M. sativa and graminaceous forages. To summarize, mixed sowing combinations between A. adsurgens and graminaceous forages are suggested to be adopted during the plantation of grassland in Ningxia Central Semi-arid Belt.