Understanding fertiliser application methods
11 November 2021 | Agriculture
Soil fertility is an important aspect in crop production as it ensures that crops are supplied with crucial elements that increase growth, production and yield.
Agribank’s technical advisor for crops and poultry, Hanks Saisai, says it is crucial for farmers to understand that the right inputs must be readily available before the start of the cropping season to ensure a successful harvest.
He explains that conventionally, soils usually supply all thirteen essential elements required by the variety of crops grown by farmers.
Crops require macro-nutrients, elements such as nitrogen, phosphorus and potassium, in large quantities daily.
Secondary nutrients such as calcium and magnesium are needed in moderate quantities and micro-nutrients such as boron, zinc, sulphur, iron and molybdenum are needed in smaller quantities to perform other specific functions.
Fertilisers are key inputs that crop farmers utilise to ensure that crops receive adequate amounts of each essential nutrient.
“Fertilisers are any materials (organic or synthetic) that are incorporated into the soil to supply nutrients that crops require for growth. However, to ensure effectiveness, it is important to ensure that fertilisers are applied correctly.”
He says there are many ways in which fertilisers can be applied and it is important for farmers to understand each method.
Firstly, fertiliser can be applied using the basal application method.
This method requires a farmer to apply fertiliser by distributing or spreading it over the crop field and working it into the soil before any planting is done.
“This method is the least likely to cause plant damage and is best for home gardens.”
Secondly, Saisai says that the top-dressing application is the distribution of fertiliser on to a field containing a growing crop and is used mainly for soluble fertilisers such as nitrate, which are easily washed into the soil and quickly available to the plant.
He says when using this method, it is advisable to do a split application during the growing season to give an extra shot of nutrients when needed by taking into consideration the different nutritional requirements of crops at different stages of growth.
“Sideband or row placement application is a third method of applying fertiliser. It usually involves placing the fertiliser in the soil at a slight distance from the seed or seedling, often five to eight centimetres to one side and three to five centimetres below the seed or plant.”
In this way the fertiliser is near enough to be used by the plant, but not close enough to injure it.
Lastly, Saisai says that fertigation is another method that a farmer can use to apply fertiliser to the soil.
This method is only compatible with water-soluble fertilisers and it is usually incorporated in the main water tanks that are used to supply water to the crop fields or gardens.
When applying fertiliser, it is recommended that a farmer understands the available nutrient reserves in the soil by testing the soil and determining how much fertiliser is to be applied to avoid over- and under-fertilisation of the soil as it may harm crops.