large-scale adoption it will be essential to develop
systems which ensure high seed quality and are
Ecosystem services
commercially viable (Shelton et al. 2005).
We doubt that an eventual recognition of the ‘new’
In the preceding sections, we showed that tropical forage
ecosystem services role of legumes will modify farmers’
legumes have considerable potential to increase
lack of enthusiasm for legumes to a marked extent.
productivity of forage-based livestock systems, while
Although promotional and educational activities, along
providing benefits to the environment. The environmental
with results from further research involving farmer
benefits, subsumed under ‘ecosystem services’, comprise
participation, might be helpful, we expect that constraints
positive effects on: soil conservation and soil chemical,
imposed by the need for management skills and
physical and biological properties; water balance;
investments will remain, unless attractive economic
mitigation of global warming and of groundwater
incentives are offered to farmers (White et al. 2013). Such
contamination; saving of fossil energy; functional
incentives should not be restricted to legume-based
technologies but should extend to all tropical forage
biodiversity (soil, entomofauna); and rehabilitation of
technologies which provide environmental services. We
degraded land. The combination of these features makes
suggest that schemes of payment for ecosystem services
tropical forage legumes particularly valuable at all levels
(PES) (Pagiola et al. 2004; Van Noordwijk and Leimona
of the system because of their interaction with plants, soil,
2010), applicable to both smallholders and large livestock
animals and the atmosphere. This environmental role
producers, be explored, developed and implemented.
could be considered as a ‘new’ important dimension of
tropical forage legumes.
The need for life cycle assessments
A crucial aspect, however, is: During past decades the
beneficial role of tropical forage legumes was promoted
Inputs of N are necessary in all pastures if livestock
with the sole focus on livestock production and soil
productivity is to be increased, such as within the concept
fertility; what must be done to have legume-based
of SI. Basically, there are 2 options: (1) planting legumes
technologies more readily adopted by farmers now that
with SNF capability in mixtures with grasses; and (2)
general environmental benefits are recognized?
applying industrial N fertilizers to grass-only swards.
Tropical Grasslands-Forrajes Tropicales (ISSN: 2346-3775)
Tropical forage legumes and environment 9
Greenhouse gas emissions from both approaches should
assessment of the impact of promising legume species
be measured. We suggest that full life cycle assessments
on rumen methanogenesis;
for tropical pastures addressing the whole carbon
identification of tanniniferous legumes which con-
footprint (Eshel et al. 2014) should be performed. In their
currently provide high quality forage in terms of
temperate climate-focused review, Phelan et al. (2015)
digestibility in the rumen and reduced methane
reported that CO2-equivalent emissions for Trifolium
emission intensity;
repens-grass pastures were 11‒23% lower than for N-
identification of anti-methanogenic compounds other
fertilized grass. Such life cycle assessments must include
than tannins in legume forage;
the need for fossil energy and any benefits to any
assessment of the BNI potential of forage legumes;
subsequent crop in a rotational system (de Vries and de
development of methodologies for payment for
Boer 2010; Jensen et al. 2012).
ecosystem services;
optimization of SNF via enhanced exploration and