Back Fertiliser application for maize crops

Date: 19 October 2015

Ensuring that crop nutrient requirements are met is a fundamental step to achieving high maize silage and grain yields. However, applying more fertiliser than required is expensive and increases the risk of nutrient losses to the environment. Growers should always soil test to determine soil nutrient status and then work with their local fertiliser company, merchant or farm consultant to ensure they do not apply more nutrients that the crop needs.

 

How much fertiliser should you apply to a maize silage or grain crop?

There are a number of steps to working out crop fertiliser recommendations.

  1. First determine a realistic crop yield target. Your local Pioneer® brand products merchant or contractor representative, can help determine likely maize silage and grain yields for the area you are hoping to plant. This information is combined with soil fertility information and used to calculate the likely nutrient requirements for your crop. While applying too little nutrients will limit yield, there is no point in fertilising for a high yielding crop if the growing environment means that it will be difficult to achieve it. Low yielding environments include those which have temperature or moisture limitations as well as those which have soil issues which cannot be addressed through fertiliser application (e.g. compaction, poor drainage or low organic matter).
  2. Soil test to determine soil nutrient levels. The normal cultivation depth for a maize crop is approximately 150 mm, therefore the soil sample should be taken to this depth. 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. Ensure that the soil sample is free of crop debris and large root pieces as these can distort nutrient levels and the physical characteristics of the soil as expressed in the laboratory report.

 Table 1: Nutrient removal rates in maize silage and maize grain1

 

Maize silage

(kg per tDM 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

 1Nutrient requirements of dairy cattle, National Research Council, 2001

 

  1. Calculate crop nutrient removal rates. Table 1 outlines the amount of nutrient removed per tonne of maize grain or silage drymatter. Multiply the removal rate per tonne of grain or tonne of drymatter (tDM) by the expected yield to calculate how much nutrient your crop will remove. Note this is not the amount of nutrients you need to apply.
  2.  Consider mineralisation during the maize growing season. New Zealand soils, especially those which have been in long-term pasture or with a history of effluent application, contain high amounts of nutrients including nitrogen, potassium, phosphorus, magnesium and sulphur in the organic matter. When the soil is cultivated the organic matter breaks down through a process called mineralisation and the nutrients it contains become plant available.

 

Your local fertiliser representative will use the crop requirement and soil supply information to calculate nutrient inputs. Crops grown in high fertility dairy farm paddocks may require little or no fertiliser input whilst those grown on repeat cropping blocks may require additional capital fertiliser inputs in order to maintain fertility levels.

Finally 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.

For more information see Pioneer Technical Insight 332: Fertiliser Application for Maize Crops.