The effects of rainfall on crop production
09 December 2020 | Agriculture
The distribution and intensity of rainfall can have a direct impact on the production of crops, fruits and vegetables.
According to Hanks Saisai, Agribank’s technical advisor for crops and poultry, rainfall provides the much-needed moisture that stimulates the regrowth of grasses and facilitates the growth of vegetables, cereal crops and fruit trees.
He says when too much rain falls in a short period of time it can have negative effects on the growth of crops.
“For instance, 70 mm/hour rainfall intensity can cause direct damage to plants by damaging the shoots, leaves and, in severe cases, the stems and branches of fruit trees.”
Too much, too little
According to him, high intensity rainfall causes physical damage to the flower, which are essential for the pollination process, which results in fruit formation.
In addition, high intensity rainfall lowers the activities of pollination agents such as bees and other insects.
In sandy areas, high rainfall intensity may leach soil nutrients from the topsoil to the subsoil, making them unavailable for crops with shallow root systems.
On the other hand, in areas with clay soils, high rainfall intensity may cause waterlogging, resulting in suffocation of plant roots due to a lack of oxygen supply.
“Ultimately, these factors hinder the desired growth of crops that are grown by farmers who solely rely on rainfall as a means of irrigation.”
Rainfall distribution is another factor that has a direct effect on the growth of crops.
“Crops need water throughout the growing phase, so the availability of adequate water in the soil is essential to enable plants (crops) to grow rapidly.”
He says it is important when relying on rainfall as a means of irrigation to know that if there is a dry spell of a week or two it may be harmful for seedlings, as they do not have established root systems that can reach water that is deeper down in the soil.
This may result in the wilting of seedlings and if no water is applied to these crop fields, it may result in crop failure. Moreover, leafy vegetables such as lettuce, cabbages and spinach may become bitter and flower prematurely.
The effect of poor rainfall distribution on fruit vegetables such as tomatoes can cause them to flower and set fruits before enough vegetative growth has been made.
“For cereal crops such as maize, sorghum and pearl millet, when the distribution of rainfall tends to be poor, they may also be forced to flower and set tassels early before the needed time for vegetative growth.”
In extreme cases where rainfall distribution is very poor, crop failure is normally high, which results in food shortages in many rural households that are actively involved in the primary production of cereal crops.
“For one to be a successful producer of cereal crops or vegetables whilst relying on rainfall, it is of great importance to pay attention to the forecasted rainfall’s intensity and distribution, as these are key factors that have a direct impact on crop growth.”