Long-term yield patterns in barley-based cropping systems in Northern Syria. 2. The role of feed legumes

Rotations of barley with feed legumes produce more biomass and crude protei n than barley-fallow and continuous barley sequences, but scope remains to improve the potential value to farmers of feed legume-based systems. This g aper summarizes B-year results from two sites from 2-year rotations of barl ey with: narbon vetch (Vicia narbonensis) and lathyrus (Lathyrus sativus), each harvested mature; and common vetch (Vicia sativa). harvested by simula ted green-grazing and mature, all in factorial combination with four NP fer tilizer regimes applied biennially to the barley. Mean yield differences between rotations were quite small. but at the drier site the narbon vetch rotation was significantly superior in both total bi omass and crop total nitrogen. Other results implied yield compensation bet ween barley and legume phases: barley performance was relatively depressed at the wetter site after high-yielding narbon vetch but was relatively enha nced at both sites after green-grazed common vetch. Evidence from year-roun d soil-water monitoring suggests that the benefit following green grazing m ay have arisen, in part, from a small carry-over of profile moisture betwee n crops not much inferior to that residual from a fallow year. Both crop ph ases responded strongly to biennial P fertilizer; and barley responded stro ngly to three rates of N-fertilizer, but a sometimes significant curvilinea r component to this response reflected a tendency for grain yields to be de pressed by added nitrogen in the driest years. But interactions between N-r ates and rotations were not significant. It was concluded that narbon vetch may have greater potential than common v etch and lathyrus for mature harvest in drier areas, but its unsuitability for grazing green is a limitation. Flexibility of utilization is important, to accommodate the needs of different farmers and the exigencies of differ ent seasons. The green-graze option has major potential where there is a de mand for high-quality spring grazing; and indications that barley may be as productive after green-grazed vetch as after a year of fallow suggest an a lternative approach for farmers who have previously avoided legumes in orde r to maximize barley production.