Maize for Silage
Technical
Insight 332

FERTILISER APPLICATION FOR MAIZE CROPS

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DETERMinING CROP FERTILISER REQUIREMENTS

The maize plant produces high drymatter yields and therefore has a high requirement for nutrients especially nitrogen (N), phosphorus (P) and potassium (K). It is not usually necessary to apply fertiliser to supply all the crops nutrient requirements. Crops planted in paddocks that have recently been in pasture can usually extract a significant portion of their nutrient requirements from the soil. There are a number of reasons for this fact:

  • Maize has a deep rooting structure (up to 1.8 m) and this allows it to utilise nutrients which have dropped below the root zone of shallow rooted pasture species.
  • Cultivation of paddocks which have been in long-term pasture can result in the release of up to 300 kgN/ha from soil organic matter.

Recent research has shown that high fertility dairy farm paddocks, including those with a history of dairy-shed effluent application may not require additional fertiliser.

Long-term maize paddocks will normally require higher nutrient inputs.

When determining crop fertiliser requirements always obtain a recent, representative soil sample. Don’t apply more fertiliser nutrients than you need. As well as being expensive, applying excess fertiliser above crop requirements can result in nutrient losses to our waterways.

SOIL SAMPLING

There are a number of factors to consider when collecting a representative soil sample.

  1. Soil sample prior to cultivation. The normal cultivation depth for a maize crop is approximately 150 mm therefore the soil sample should be taken to this depth. Soil pH and nutrient levels decrease as soil depth increases. The decrease can be especially large in low fertility environments or where soil fertiliser application has been limited. Ensure that the person making the fertiliser recommendation is informed if the cultivation depth will be greater than the sampling depth as additional lime and fertiliser may be required.
  1. Choose soil sampling sites carefully. If the area has recently been in maize, ensure that the samples are collected representatively across the paddock and from the central area between the rows of stubble. The main reason for this is that if the sample is inadvertently taken from an area where the starter fertiliser was banded, any residual product will give elevated readings. This can be significant since 250 kg/ha of banded starter fertiliser could be equivalent to as much as 3.75 tonnes of the same product broadcast per hectare.
  1. Ensure that the soil sample is free of plant or crop debris and large root pieces. Plant material can distort nutrient levels and the physical characteristics of the soil as expressed in the laboratory report.
  1. Look for variations in soil test results. If the annual soil test report for the same paddock shows significant variation in CEC, volume weight or phosphorus levels from year to year check the sampling protocol. Paddocks that are regularly cropped for maize should not show large variations in these test results between seasons.
  1. Deep N soil test after planting and before applying additional nitrogen. Take a deep N (60 cm) soil sample 2 - 4 weeks after planting to determine whether your crop requires any sidedress nitrogen. Your fertiliser representative can arrange soil sampling and interpretation of the deep N soil test. Deep N results can be run through AmaizeN, a fertiliser forecasting tool developed for maize, to determine whether additional N is required.

DETERMINING FERTILISER INPUTS

Crop yields will be decreased if nutrients are limiting. Maize nutrient removal rates per tonne of maize silage drymatter or maize grain are shown in Table 1.

Table 1: Nutrient removal rates in maize silage and maize grain

 

Maize silage (kg per tonne of DM harvested) 8% crude protein

Maize grain (kg per tonne of dry (14%) grain) 9.5% crude protein

Nitrogen

12.8

13.1

Phosphorus

2.6

3.0

Potassium

12.0

4.2

Magnesium

1.7

1.2

Sulphur

1.4

1.0

Reference: Nutrient requirements of dairy cattle, National Research Council, 2001

Your local fertiliser representative or Pioneer representative can help you determine fertiliser input levels taking into consideration a number of factors including likely crop nutrient removal rates and the amount of nutrient potentially available in the soil.

TIMING OF FERTILISER APPLICATION

In some cases the combination of large amounts of high salt index fertilisers (e.g. murate of potash) applied immediately prior to planting with a starter fertiliser can cause fertiliser burn to the roots of seedling maize plants. Affected plants have damaged root systems and this will affect nutrient and moisture uptake as well as plant standability. For this reason it is recommended that on light soils, particularly where a large amount of base or capital fertiliser is required, it is applied and incorporated into the top 50 - 75 mm of the soil, at least seven days prior to planting.

As previously discussed, some crops may require additional nitrogen to be applied as a side dress application. Side dressing should occur when the plants are between calf and knee high.

STARTER FERTILISER PLACEMENT

Incorrect placement of the starter fertiliser can also cause fertiliser burn to the roots of young plants. This is more common on light soils. If using moderate-high rates of starter fertiliser (e.g. 250 kg/ha of DAP or 375 kg/ha of 12:10:10) banding a minimum of 50 - 70 mm away from the seed is a good insurance against fertiliser burn.

Worn planter fertiliser disc opener mountings can result in the fertiliser being placed close to and even right on the seed line on sloping ground or curved rows and corners. The subsequent damage to the maize plant results in a “D” shaped rooting system. If plant lodging occurs as a result of this problem, the plants normally lodge outward from the centre of the planter run.

PEAT SOILS

When planting maize on run-out peat pasture the application of 150 - 200 kg/ha of Sulphate of Ammonia is recommended. For more information see the Pioneer Technical Insight No 315: Cultivating Peat Soils.

MICRONUTRIENT REQUIREMENTS FOR MAIZE

Micronutrient deficiency is seldom a problem in maize crops however deficiencies sometimes occur on light or peat soils.

  1. Test for micronutrients. Minor element deficiency can be corrected during the early vegetative growth stage of the crop. Submit plant samples for laboratory testing for micronutrient analysis. Care should be taken to ensure that the plants selected are completely free of soil. Do not wash plants.
  2. Boron. In modern maize hybrids a lack of cob tip fill is normally associated with a period of moisture stress in the 14 day period leading up to pollination. Boron deficiency can also cause a lack of tip fill but this is extremely uncommon. Boron toxicity results in plants turning white. This can occur if there has been an oversupply of boron in the base fertiliser. Boron toxicity is most commonly found where there has been an overlap with the bulk spreader (often in the middle of a paddock), especially in the second season of maize growing after the application of boron.



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Revised: June 2015
Expires: June 2018