Discussion and Conclusions

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