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Red Clover Silage

Red clover herbage harvested for silage contains around 25 kg of K and 3 kg of P per t DM. Harvesting 15 t DM per ha per year removes a huge amount of K in particular and this needs to be replaced by slurry or artificial fertilizer. To avoid luxury uptake of K and subsequent problems with milk fever in cows, K fertilization should take place in advance of each crop. For example, if you plan to harvest a first-cut crop of 5 t DM per ha in mid-to-late May, this requires 125 kg/ ha of K and 15 kg/ha of P during March or early-April. It is best to hold off spreading slurry until ground conditions are such that avoids any damage to the crop. A light grazing in the spring and in the late autumn is possible although this can shorten the longevity of the red clover content of the sward.

Red clover conservation

Red clover is characterised by low dry matter and low water soluble carbohydrate concentrations and a high buffering capacity. As a result, it is more difficult to obtain a satisfactory fermentation with red clover than with all-grass silage. 

It is advisable to wilt for 24 to 48 hours in dry conditions to achieve 25-35% dry matter concentration. This will also concentrate sugars to encourage a desirable fermentation and reduce silage effluent production. Leaf is prone to shatter and it is advised not to use a conditioner mower. Avoid overwilting and excessive handling that can result in substantial leaf shatter and loss. It can also be difficult to consolidate very dry material in the silo.

Red clover wilted to 25% dry matter will often ensile effectively without an additive. However, where herbage is wet or where there is a very high proportion of red clover, an effective additive can be used to ensure a stable fermentation.

Making silage

The optimum harvest date for first-cut is around 20 May and subsequent harvests at 6-to-8 week intervals. 

Experience at Teagasc Solohead, along with evidence from elsewhere, is that red clover makes reasonably good quality silage with slightly lower digestibility than fertilized ryegrass swards. High volumes of cheap (in terms of N fertilizer input) silage are produced with very high intake characteristics, which is a redeeming characteristic of red clover silage. High intake compensates for somewhat poorer nutritional characteristics and cattle perform well on red clover silage once it is well-preserved. 

Target harvest dates are 15 to 20 May (yielding approximately 5-to-6 t DM per ha), early to mid-July (4-to-4.5 t DM per ha) and late August or early September (3-to-3.5 t DM per ha). Large quantities of herbage (>2.5 t DM per ha) can build up during September and October and it is important to remove this before the winter. Otherwise there can be large losses of herbage due to senescence and heavy covers can damage the clover content over the winter. The approach used at Teagasc Solohead is to zero-graze under good ground conditions during late October and November leaving swards ‘cleaned out’ to the butt over the winter.

Table 1. Analyses of first-cut red clover silage at Teagasc Solohead in 2021 

Silage analysesResultsDesirable valuesStatus
Dry matter (DM) % 42 20 - 30  
pH 4.4 4.0 - 4.7 Good
Ammonia N - % 2.7 <10 Good
Ash - % 8.5 <8.6 Good
Neutral detergent fibre - % 45 <45 Good
DM Digestibility 71 >69 Good
UFL - per kg DM 0.79 0.65 - 0.90 Good
ME - MJ/kg DM 10.2 >9.8 Good
Crude protein - %  12.3 13.5 - 17.0 Low