High density silvopasture systems for quality forage production and carbon sequestration in humid tropics of Southern India

In comparison to conventional grass monoculture practices, well managed silvopasture systems with high tree densities have greater potential for quality forage production and climate change mitigation via carbon sequestration in humid tropics, but needs quantification on above aspects for popularizing among farmers and for payment of ecosystem services. We therefore investigated the comparative forage and crude protein (CP) yields and carbon stocks of six different fodder production systems, viz; 3-tier hybrid Napier (HN)+mulberry+stylosanthus system (planted in 3:1:1 ratio, area basis), 2-tier HN+mulberry/stylosanthus (3:2 ratio) and HN/mulberry/stylosanthus monoculture systems and one control plot with natural grass vegetation, for 2years. Trees were planted at 60x60cm spacing, pruned at 1m height at 3months interval. At the end of 2years, HN monoculture produced significantly higher dry fodder yield (51Mgha(-1)) (P<0.001), followed by HN+mulberry (48Mgha(-1)) and 3-tier system (43.35Mgha(-1)). The CP yields followed the trend mulberry monoculture>HN+mulberry>3-tier system, whereas CP yield was significantly lower for HN and stylosanthus monocultures and their combinations. Carbon stocks were significantly higher (P<0.001) for mulberry monoculture (174.84Mgha(-1)); followed by 2-tier HN+mulberry (147.67MgCha(-1)), which captured 11-13% more carbon than 3-tier silvopasture and HN monoculture systems. However, fodder yields from mulberry sole plots were lower. HN monoculture out yielded all other systems in fodder yields, but fodder quality as indicated by CP yield, as well as carbon storage was comparatively poor. Hence, considering the fodder (24Mgha(-1)year(-1), dry basis) and CP yields (3.15Mgha(-1)year(-1)), and carbon fixation rates (11MgCha(-1)year(-1)), 2-tier HN+mulberry system with tree density of 11,111 treesha(-1) was found to be the most promising system for meeting both farmer needs and environmental services. Adopting these systems in at least 3Mha can supply 72 and 9.45Mt of dry matter and CP respectively, which can meet one-third of the annual dry matter and crude protein deficit of Indian livestock industry and half of the carbon emission standards of India's INDC commitment over a period of 10years.