For exact details on Artificial and Organic Fertilisers see the section entitled ‘Fertilising’ in the Silage Project.
Before fertilising it is important to carry out a soil test as a lot of money could be saved if unnecessary fertilisation is avoided.
All fertilisers should be applied pre-sowing. 16% of the phosphorous can be applied during sowing, as this nutrient is needed for germination.
As regards maize, it is a crop that responds very well to the use of cattle and pig slurry. On average, 14,400 – 16,800 gallons/ha of slurry will provide adequate phosphorous and potassium at soil index 3 and above (soils at or above 7ppm of P and 100ppm of K). Slurry should be applied in spring and ploughed in immediately to retain the nitrogen content. For soils with low potassium levels, 125kg/ha of muriate of potash should also be added. If no slurry is used, the same crop requires 40kg of phosphorous and 190kg of potassium (yield of 15tonnes/ha).
One of the advantages of maize is that it has very low nitrogen requirements when compared to grass. Nitrogen is made available to the crop from organic manure (slurry and FYM), soil nitrogen and artificial nitrogen fertiliser. While the organic manures have the potential to supply all the nitrogen requirements, it is very difficult to estimate whether enough has been supplied. The soil can supply nitrogen from 40kg to 400kg per hectare so this makes it also difficult to know how much nitrogen is available for the plants. Therefore, to calculate the nitrogen requirement of maize, one must estimate the yield, e.g. for a 15tonne/ha yield, 180kg/ha of nitrogen will be required. If slurry is used to provide phosphorous and potassium, a straight fertiliser (Urea or CAN) must also be used to supply adequate nitrogen. However, it is important not to use too much nitrogen, as this is costly, delays maturity and lowers the starch content.
Examples of the most common fertilisers used are 27.5:2.5:5 (Pasture Sward) and 24:2.5:10 (Cut Sward).
This macronutrient is especially important for maize as it encourages crop establishment, root development and early crop growth. Therefore, adequate phosphorous is essential for optimum yield and quality.
Phosphorous Deficiency Symptoms of Maize:
Dark green leaves
Tips of leaves may ‘burn off’
Purple or red coloration on stems and leaves
The leaves turn yellow and may eventually die.
Scorching of the outer margins of the leaves.
Zinc is the most widely deficient micronutrient for maize. A deficiency affects early crop development and growth as well as yield potential and crop quality. If a deficiency has been identified, zinc sulphate (5kg/ha), zinc chelate or an inorganic formulation (as required) must be sprayed. Symptoms are usually evident during cold weather in April and May. Sometimes they can be seen even if minor element levels are adequate, so a soil analysis should always be carried out before treatment.
Zinc Deficiency Symptoms of Maize:
Pale yellow stripes parallel to the leaf midrib starting at the base of the youngest leaves. Leaf midribs and margins remain green.
Red colour of leaf edges and stalks if severely affected
Partially filled cobs at harvest
On low magnesium soils, magnesium deficiency may be a problem. To solve this, magnesium limestone or Kieserite must be applied. If a deficiency has been identified, the crop should be treated with magnesium chelate or an inorganic formulation. Symptoms are usually evident during cold weather in April and May. Sometimes they can be seen even if minor element levels are adequate, so a soil analysis should always be carried out before treatment.
Magnesium Deficiency Symptoms of Maize:
White or yellow stripes between leaf vines.