Sweet clover (Melilotus officinalis) is generally used as a soil improving green manure in the UK. It will help to fix nitrogen in the short to medium term. It can also be a component of some diverse grazing mixtures. Sweet clover will also be planted for pollinators and to a lesser extent, for game cover.
Sweet clover (also known as yellow blossom) is a tall biennial plant, dying off after flowering for a couple of years.
It is important to remember that the plant can set seed easily and come back in subsequent crops, proving problematic in an organic rotation. In this case, volunteer plants should not be allowed to contaminate subsequent cereal crops. Even a small amount can cause coumarin taint, which can lead to rejection of malting barley in some cases.
Sweet clover has a fast developing deep rooting system which is very useful when growing on light, sandy, free draining soils.
When to Sow: April - May is the ideal time for sowing in the spring. Mid to late August is the best time for autumn sowing. Establishment is less likely to be reliable if sowing extends too far into September.
Sowing Rate: 1.5 g/m2 - 6kg per acre - 15kg per ha.
Preparation:The most successful results come from sowing into a newly prepared seedbed. Aim to cultivate the top soil to about 5cm, with a light cultivator or discs. The finished seedbed should be fine but firm, with no clods. Several passes with a cultivator may be needed to achieve this.
Sowing: Clover seed is small and should be broadcast or drilled to a shallow depth (no more than 10mm). Sowing too deep will reduce the germination dramatically. The soil should be rolled after sowing to increase seed to soil contact.
Management: Sweet clover does not take kindly to hard topping. Top at 10cm above the ground to avoid damage to the plant crown if annual weed control is necessary.
As a winter hardy plant, sweet clover can be a useful component which needs to last 12-18 months. It can effectively be terminated by ploughing, the crown of the plant must be terminated and buried to kill it off reliably.
Date Posted: 13th January 2023