April is fast approaching, and with it the maize-sowing season, making now onwards a good time to create a planting plan.
With this is mind, Agriland is looking at the properties that the crop needs to thrive, beyond the basics of good soil structure, adequate soil moisture and warm soil temperatures.
According to the Potash Development Association (PDA) maize - which it says can easily produce 50t/ha in a period of four months - has a large demand for nutrients.
Nutritional requirements of maize crops
Like many other crops, maize requires three primary nutrients - nitrogen (N), phosphorous (P) and potassium (K).
According to the PDA, P is particularly required by the growing tips of the plant, hence it's importance for root growth.
Any shortage, the association says, especially in the very early stages, reduces root growth and nutrient uptake which can adversely affect the growth of the crop for the rest of the season.
The PDA says typical phosphate crop removal is 1.4kg phosphorus pentoxide (P2O5)/t fresh crop – that is 55 kg/ha P2O5 for an average 40t/ha forage crop, it adds.
Crop removal is the amount of nutrients removed from the field in the harvested portion of the crop. It is calculated by taking the concentration of each nutrient in harvested material and multiplying by the harvest yield
Potash (K) is the nutrient required in the greatest amount by maize, according to the PDA, which adds that an average 40t/ha crop takes up around 360kg/ha potassium oxide (K2O) by early August.
The demand for potash is particularly large in the period of rapid growth and the crop needs to take up about 8kg/ha K2O/day.
The soil must be able to supply both the total demand of 360kg/ha and the daily requirement of 8kg/ha without any hindrance. This requires an adequate level of readily plant available soil potassium.
During maximum periods of growth, the maize plant will contain more potash than nitrogen, the PDA says, adding that maize removes large amounts of potash, which must be replaced to maintain soil fertility.
Potassium, according to the PDA, is essential for regulating the water content; transporting sugar from the leaves to the storage organs, where sugar is converted to starch; and maintaining the rigidity of plant tissue, which is necessary to remain fully extended.
Plants well supplied with potassium also seem to be less susceptible to fungal and pest attacks, the association adds.
Magnesium (Mg) is an essential element in chlorophyll and, hence, for photosynthesis.
Crop removal is 40kg/ha magnesium oxide (MgO), according to the PDA.
The total requirement (to be supplied from manure and fertiliser) should be related to the magnesium level in the soil and additional magnesium is only justified at soil index 0 when 50-100kg MgO/ha should be applied every three to four years, the association says.
Lastly, the PDA discusses sulphur, a constituent of protein together with nitrogen. Few maize experiments have tested the need for sulphur, it says, but deficiencies are possible where soil sulphur levels are below optimum.
According to the PDA, maize is not very sensitive to trace element deficiencies, but boron, copper, zinc, manganese and iron may occasionally be deficient on soils where manure is not applied regularly.
