Beware Contaminated Bales
Baled silage can be prone to soil contamination due to dust and slurry being incorporated into bales. Shane Brewer, from agricultural testing specialist Eurofins Agro UK, suggests that if slurry is not incorporated into the soil, the crop will not see the full benefit, and any residues risk contaminating bales with harmful bacteria such as enterobacteriaceae. He explains that high applications followed by dry weather can also cause the fibre from the applied slurry to lift up into the crop, but this can be detected by accurate ash analysis.
Normal ash levels in the plant should be around 6% to 8%, depending on the crop. Higher numbers indicate additional mineral content which will have occurred due to soil being incorporated into the bale. Soil can contain clostridia, spores and enterobacteria, which can be become a challenge to overcome.
Mr Brewer says that a test will show contamination by providing data on Volatile Fatty Acids (VFAs) suggesting that contaminated bales will be high in butyric acid and low in lactic acid, causing dry matter losses. He says a slower fermentation in the bale will be shown in a higher than optimal pH level, which will lead to the bale not storing well and losing protein.
Pre-cut, dry NIR tests should be carried out to establish sugar levels and nitrate content. During the cutting and baling process, soil can be incorporated into the bale which can lead to potentially harmful bacteria being present in the forage. A higher pH, combined with spoilage and harmful organisms, can result in moulds and yeasts growing, resulting in further dry matter loss and potentially producing mycotoxins which can cause health problems in livestock and impact on productivity.
Andy Hayhurst, from slurry application specialist Vogelsang, suggests that a trailing shoe applicator is the best way to minimise contamination. He says that a trailing shoe will part the crop and apply slurry directly to the soil.
Vogelsang’s BlackBird trailing shoe has a beak shaped applicator to part the crop and slow the flow of slurry before it reaches the soil, which reduces contamination. The pointed shape also helps the applicator to penetrate the soil to help slurry absorption.
Working widths of the BlackBird range from 7.5 metres to 30 metres and there are a variety of models in the range, including Single, Light, Pro and Max. Mr Hayhurst says that, in this year’s dry conditions and with the risk of heavy showers on very dry soils, operators should look to minimise run off and improve nutrient utilisation by choosing a trailing shoe.
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