Standing residual biomass is the ability of vegetation to maintain, after its growth period (mature vegetation), a correct feed value (yield, nutritional value, and palatability). It is also a livestock farming technique to manage the balance between grazing and stored fodder, applicable in all systems using diversified vegetation.
Standing residual biomass of vegetation allows to:
Graze or mow late: with a residual period ranging from 1 to 8 months after the heading of grasses. If we accept that ruminants digest fibers and benefit from them to meet their needs, it is possible to implement the standing residual biomass technique. "Late use of certain plots is practical because it is impossible to be in phase everywhere with grass growth."
Secure the feeding system: standing residual biomass reduces the need for harvested fodder and adapts to seasonal weather variations. It is not uncommon to see farmers mow in May to distribute hay from late June. However, the cost associated with mechanization for harvesting and distribution is significant in farm accounting. This can provide security through grazing in summer or winter depending on hay stocks.
Create grazing resources in summer or winter: distribute fodder availability. Heterogeneous environments have good standing residual biomass, and it is possible to feed high-demand cattle even in summer on this type of vegetation. These vegetations can be grazed when other areas no longer grow.
Improve the feed value of pastures and facilitate turnout: mix refusals and regrowth to offer a better fiber balance in the ration and avoid crushing or mowing refusals. In regrowth, leaves are abundant and fibers absent, which can cause acidosis in animals.
Identify vegetation with good standing residual biomass aptitude
Standing residual biomass is high in diversified and heterogeneous environments such as wetlands, undergrowth, moors, lawns, and meadows rich in species. It depends on the flora and environmental conditions.
Underlying processes
At the plant scale
Some plants retain their nutritional value even after flowering, their aerial parts remain green with good resistance to drought. Conversely, aerial parts of the most productive and early grasses degrade quickly during growth (leaf and stem senescence).
Regrowth is in vegetative growth and has no programmed stop due to flowering. They therefore have greater residual capacity, if climate permits.
Standing residual biomass promotes plant reserve accumulation and thus their growth capacity.
Defoliation slows or stops seed setting and restarts vegetative growth.
Feed availability according to vegetation standing residual biomass aptitude
At the vegetation scale
Flora diversity spreads out the overall growth of vegetation.
Bushes and trees create a parasol effect and shelters, maintain coolness and offer edible foliage or fruits until autumn.
The "strawy" layer protects regrowth or seedlings, late in the season (drought, wind, snow...).
In practice
Good standing residual biomass aptitude
High diversity of grasses and other plants
Plants with good aptitude: grasses with fine or round leaves dominant (purple moor grass, canary grass, wood false-brome, carex, rush, legumes...)
Shrubs, trees, strong environmental heterogeneity (parasol effect until winter)
Wet environment, good water reserve
If you rub a mature plant between your hands: leaves are resistant, flexible, not sharp or leave green traces.
Poor standing residual biomass aptitude
Low floristic diversity
Little environmental heterogeneity
Plants with poor aptitude: grasses with broad leaves, productive and early (tall fescue, orchardgrass, reed canary grass, velvet grass, annual meadow grass...)
Early lawn (brome dominant...) more or less degraded (couch grass, exhaustion indicators...)
If you rub a mature plant between your hands: leaves crumble or turn to dust, abundance of necroses.
Herd skills to valorize mature vegetation
Forages with good standing residual biomass have good feed value as long as they are voluntarily consumed by the herd.
Underlying processes
The presence of bushes favors standing residual biomassZootechnical performance is associated with the amount of nutrients ingested and not just their concentration in plants.
Animals accustomed to eating fibrous forages manage to digest plant cell walls (specific ruminal flora).
Diversity stimulates appetite: diversity of vegetation formats (small and large bites) increases animals' feeding motivation at pasture and at the trough (stimulates ingestion). The amount ingested can be double the expected, especially when several complementary vegetation types succeed along the animals' path.
Ingestion speed of coarse forages is fast (large bites), which improves overall intake during meals.
Consumption of fibrous forages requires rest and rumination phases (rumen emptying time). This directly affects appetite.
In practice
First observe the standing residual biomass situation on the farm and its potential benefits. Check herd skills and encourage animals to learn to consume fibrous forages (discovery from weaning of young, competent adults, etc.).
In plots used for residual grazing, avoid favoring plants reputed as better forages because they are early and do not tolerate standing residual biomass well. Plan in the grazing sequence a dietary transition towards increasingly fibrous vegetation. Avoid demotivating animals by providing unsuitable distributed forages; instead, provide supplements that stimulate fiber ingestion or digestion.
Build paddocks integrating diversified vegetation and functional resting areas (reception for the whole herd). Respect animals' activity rhythm and extend grazing time (example: graze animals at night in summer, as they rest during hot hours).
Standing residual biomass grazing techniques consist of decoupling plant growth periods from animal grazing periods. This means letting grass accumulate without harvesting or grazing to keep the produced biomass for later. Residual grazing can be practiced over very variable durations, depending on species intrinsic aptitude and environmental conditions, ranging from a few weeks to over 12 months.
Standing residual biomass: deferred consumption of vegetation growing in spring and autumn
Managing standing residual biomass according to seasons
