BSc-MSc (Integrated)

The research project entitled “Carbon storage potential of intensive
silvopasture systems in humid tropics of Kerala” was carried out at Instructional
Farm, College of Horticulture, Vellanikkara during 2013-2015, in existing 2 year
old intensive fodder production systems, to assess their carbon storage potential
and associated soil fertility changes.
Comparative carbon storage efficiency of six different fodder production
systems viz; 3-tier hybrid napier (HN)+ mulberry+ stylosanthus system, 2-tier
HN+ mulberry/ stylosanthus systems and HN/ mulberry/ stylosanthus
monoculture systems and one open plot with natural grass vegetation as absolute
control was assessed in randomized block design replicated thrice. The 3- tier
silvopastoral system consisted of grass, trees and herbaceous legumes in 3:1:1
ratio, 2- tier systems contained grass + tree/ legume in 3: 2 ratios on area basis,
whereas the entire area contained either grass or legume or tree for monoculture
treatments. Trees were planted at a high density (11111 trees ha-1) at 60 cm x 60
cm spacing and maintained as hedges of 1m height by harvesting at 3 months
interval. All other crops were planted and harvested as per state recommendation.
Fodder yields from various systems and carbon storage in plant biomass and soil
was assessed for two years.
Among various systems, mulberry monoculture captured the maximum
carbon (211.23 Mg ha-1); 81% of which form permanent carbon stored in
standing, root biomass and soil and 19% as labile carbon in harvested biomass.
The second best system was 2-tier HN + mulberry (177.14 Mg ha-1), which
captured 13 % more carbon than 3-tier silvopasture and HN monoculture systems.
However, despite the higher carbon storage potential of mulberry monoculture,
the fodder yields were significantly lower than HN+mulberry system. HN
monoculture outyielded all other systems in fodder production, but carbon storage
was comparatively poor. Hence, considering the fodder production efficiency and
carbon storage capacity, 2-tier HN+mulberry system was found to be the most
promising system for meeting both farmer needs and environmental services.
Moreover, higher protein content in mulberry adds to the quality of the forage,
which is an important factor in economic milk production.
Variations in soil physical properties and nutrient status were assessed
after two years. In general, soil physical properties were favourably influenced by
tree based systems as compared to others.The least and comparable bulk density
(1.45 g cm-3) was recorded in HN+mulberry and HN monoculture system. Soil pH
and water holding capacity considerably improved in mulberry monoculture
(7.283) followed by 2-tier HN+mulberry system (6.36). Soil temperature was also
higher in tree based systems. The 3-tier systems were found to be superior to
monoculture systems but inferior to 2-tier HN+mulberry system with respect to
soil physical properties.Comparing the soil nutrient status, the total N, P, K and
available P content was higher in stylosanthus based systems, whereas the
available N and K content excelled in mulberry based systems. Hence, 3-tier
HN+mulberry+stylosanthus system seemed more favourable for replenishing soil
fertility as well as nutrient availability. However, stylosanthus being a poor fodder
yielder, substituting it with a suitable high yielding leguminous fodder tree can
take care of both the forage yields as well as the soil fertility aspects.
To conclude,the current research brings out the suitability of intensive
silvopasture systems with high yielding grass species (HN) and densely planted
fodder tree hedges (mulberry @ 11111 trees ha-1), for maximizing quality fodder
production and carbon sequestration and favourably influencing soil physical
properties in humid tropics of Kerala. However, the above system could not
contribute much to soil fertility owing to the non leguminous and exhaustive
feeding behaviour of mulberry and HN. Hence, inclusion of a leguminous fodder
tree along with mulberry and HN can take care of both the forage yields as well as
the soil fertility improvement.