Crop production: Get the most from your fertiliser

It is possible to increase profitability and reduce risk if you use fertiliser to best effect on your farm.

Increasingly expensive input costs are always of concern to farmers and efficient fertilisers and fertilising practices will help them to cope with this challenge.

Also read: Farm management: Controlling input costs


To calculate how much fertiliser you need, you will have to have a soil analysis done and to establish a target yield.

Soil analysis is crucial in fertiliser planning.

  • Firstly, you have to follow the correct procedures in taking the samples.
  • If the sample does not represent the specific field or production unit, the final result – or for that matter the profit – might not be positive.
  • The interpretation of the analysis must be soil- and crop-specific.
  • Analysis of the nitrogen in the soil can be a great help; if there is a surplus in the soil, it can be taken into account when determining fertiliser needs.
  • It is extremely important to take nitrogen samples within soils that are more or less the same. Remember: soil properties influence nitrogen dynamics directly.
  • Determining the target yield is as crucial as a representative soil sample.
  • These 2 factors will prevent under- or over-fertilisation which can be detrimental to profit.
  • Over-fertilisation increases the input cost unnecessarily, and under-fertilisation decreases yield and therefore also income.

Also read:
How to test soil life and health
How to use fertiliser to restore degraded soil
How to build soil fertility with organic fertiliser


Do not neglect liming.

Experience has shown that liming is often regarded as being less important when finances are under pressure – often with catastrophic consequences. If conditions are extremely acidic, it could, from an economic point of view, be more beneficial to lime instead of increasing the fertiliser application rate.

The harmful effects of high acidity on the development of an efficient root system decreases the availability of phosphorus and inhibits the efficient uptake and use of water and fertiliser. Another risk is that herbicides used on acid soil usually do not work.  The effect of micro-organisms in the soil is also suppressed in acid soils.


  • This aspect was neglected in the past.
  • The value of micro-organisms in the soil should not be underestimated.
  • The positive influence a well-balanced, healthy micro-organism population has on the availability of plant nutrients is well-documented.
  • Consult an expert for advice.

Also read:
Manage your soil fertility
Maintaining soil health – make your own compost


More concentrated products can also help to reduce fertilisation costs, as you will save on transport costs. The downside is that, in general, concentrated pro¬ducts do not contain the same quantity of secondary elements as less concentrated ones. So, compare the pros and cons before making a decision.

Consider, too, using organic fertilisers such as manure and compost, in specific circumstances. The low concentration of plant nutrients in these products can result in higher transport costs, so in most cases inorganic fertilisers have to be combined with them to enrich them and balance the nutrients.


How you apply fertiliser also has an effect on its efficiency.
In general, administering fertilisers in a band is much more efficient than broadcasting.
Some nitrogen products can be broadcast on narrower rows.
Foliar sprays are also a way of rectifying any shortages later in the growing season and are especially useful in the case of micronutrients.

Also read: Make a plan to apply top dresser fertiliser


This method ensures that the whole field is fertilised according to soil analysis and expected yield, without the fear of over- or under-fertilisation on specific sections.

  • The availability of historical yields, as well as soil chemical and physical information, are all powerful tools in optimising fertilisation.
  • Differential fertiliser application can save a lot of money, increase yield and reduce risk.
  • If producers have access to the equipment, they are in a perfect position to optimise their fertilising practices.


The availability of water in the soil is another important factor in the optimal use of fertilisers. If the crop in a specific field withers, the fertiliser is largely wasted.

Farmers will have to put in a great effort to determine beforehand how much water there is in each field. Fields that do not have enough water available initially should be considered too risky for planting. A better plan would be to plant less in order to cut down on the total risk and financial exposure.

Also read: Irrigation – which system should you use?

Effective weed control and soil cultivation are two more ways to obtain optimal fertiliser reaction. Unfortunately, a lot of water and nutrients are consumed by weeds which means they are not available for the crop. The aim of soil cultivation is to promote the infiltration of water into the soil and enhance root development. This enables the crop to make the best use of fertiliser and water. It is always importance to cultivate soil properly.

Also read: Crop production – do not neglect weed control


This has become a vital part of the nutritional management of crops and is an excellent way to evaluate your fertilisation programme. Samples, taken regularly, will enable farmers to identify any possible shortages in plenty of time. And this, in turn, will prevent not only yield losses caused by nutrient deficiencies but also the unnecessary application of fertiliser.

If these practices are followed, input costs and income can be optimised, risk can be reduced and profitability increased.

  • This article was written by Thinus Louw and first appeared in Farming SA.

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