Forage Maize Fertiliser Requirements

Why Maize?

Maize makes high quality silage for dairy cattle, beef and sheep at less cost than silage made from grass. Research has shown that maize silage in the diet of dairy cows increases forage intake, milk yield and milk protein content. Supplementation with concentrates can be reduced and profitability is improved. New varieties have increased the opportunities to grow this crop successfully in more and more areas of the UK and the area grown increased dramatically through the 1990s and by 2007 was approaching 150,000 ha.

Area of maize grown in the UK

Correct manuring

Correct manuring is vital to the success of the crop because it greatly influences not only the yield and of the crop and its nutritional content but also growing costs. Growing maize is attractive because it offers a good opportunity for the use of slurry; 80-90% of all maize crops receive manure of some kind. Frequently the nutrient contribution of slurry and manure is not taken into account when determining the amount of fertiliser to apply. It is also important not to exceed environmental guidelines for organic manure application. Soils receiving regular large amounts of slurry should be sampled and analysed periodically to ensure that appropriate levels of readily available plant nutrients, especially phosphate, are not being exceeded. This leaflet explains the principles of fertilisation and provides the most up to date recommendations for forage maize.

Yield and quality

Average yields are around 40 tonnes/hectare fresh weight with typical dry matter (DM) of 30%. This equates to a DM yield of 12 t/ha. Growers on favourable sites can achieve fresh yields of well over 60 t/ha. The feeding value of the cob portion is almost double that of the rest of the plant. At harvest, the cobs should form at least 50% of the crop dry matter to give a high quality feed.

Maize silage is commonly used to provide up to 75% of total forage in the diet and on this basis, 1ha of maize can provide for 6-10 cows depending upon yield.

The protein content is lower than required for most livestock so protein supplementation with rumen digestible protein (RDP) is necessary.

Site and soil

Maize is very sensitive to temperature and a favourable site is the key to success. Most areas of England and Wales are suitable provided that the site is below 400 feet in altitude. South facing sheltered sites are best.

The soil should be free-draining, have good reserves of moisture and be without compaction problems unless these can be remedied by subsoiling. Friable, well-structured soils allow the preparation of good seedbeds and easy rooting. Heavy soils are disadvantaged by the problems of obtaining a good seedbed in spring and the possibility of harvesting difficulties in a wet autumn. Shallow and gravelly soils run the risk of poor crops in dry years. Maize is such a useful crop that it is not worth taking risks by growing it on drought-susceptible soils.