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To measure is to know – the importance of crop estimates

May 2020

Gavin Mathews, Bachelors in 
Environmental Management. Send 
an email to gavmat@gmail.com

Doing a crop estimate is a method of measurement and forecasting whereby analysts or farmers predict or estimate the potential tonnage of a particular crop. This may be for a certain field or for a farm or even nationwide. Therefore, we can divide estimates into two categories; national crop estimates and personal crop estimates.

The national crop estimate is the forecasting of the expected harvest for the entire country. This is performed by a dedicated team of analysts and economists who use a combination of methods to determine a given tonnage figure. This figure will change throughout the season as the conditions change.

Estimates will be done at different stages throughout the season to try and be as accurate as possible. The methods used to perform the crop estimates are based on information available through the season. Firstly, the committee will look at the inputs that where purchased pre-season. How much seed are farmers hoping to put in the ground? Obviously, all the seed that is bought will not be planted as climatic conditions will vary across the country. To determine how many hectares are actually planted the estimates committee will travel the country to assess the conditions as well as make use of geographical information systems (GIS) and remote sensing technologies to arrive at an accurate answer.

As the season progresses the team will make continual adjustments based on regional conditions throughout the country. If you are receiving good rains, this does not mean that the rest of the country is. The average South African maize harvest varies dramatically year on year as our climatic conditions are so volatile. The long-term average maize harvest in South Africa is approximately 8 million tonnes. However, we have regularly achieved above the 10 million tonnes mark. In 2017 South Africa achieved a record harvest of over 16 million tonnes and all indications suggest that 2020 may well achieve the same if not higher.

Doing a crop estimate is an important practice because maize is the staple food for our country as well as Africa. Approximately 200 million Africans consume maize on a daily basis. Knowing how much maize is available in the market will determine how much you and I will need to pay for it at the supermarket.  Therefore, crop estimates contribute to the price setting mechanisms of the market. 

There are many other products which prices are also indirectly determined by the maize price such as livestock. Knowing how much maize will be available at harvest time will also allow us to manage and budget accordingly. Perhaps in a poor season we will be prompted to hold back on exports and rather keep reserves for our own countries consumption. In a good year we may have the freedom to push exports or perhaps dedicate a larger percentage into animal production. These are all decisions that the crop estimates aid us in making.

Many of these reasons for doing crop estimates are similar for the individual farmer. Farmers will do personal crop estimates in order to budget and plan for the coming season. The tonnes that you expect to harvest have a direct influence on your potential profits. Farmers who run mixed operations where livestock is a part of the business structure will be able to plan and strategise for optimum profits by deciding where the grain will make the most impact. Many farmers sell maize silage and doing a crop estimate will allow them to market their silage according to a dry grain crop estimate. Doing a maize estimate in each field is a good practice as it allows you to assess your performance throughout the planting season. It also assists you in analysing your fertilisation programme. 

Farmers usually use simple mathematics to calculate their yield estimates. This is done by measuring a row section in the field and counting the number of plants in that section. The farmer will then count the number of cobs on each plant and then do a kernel count on each cob. By weighing a sample of kernels, the farmer can then calculate the kilograms of grain that will be harvested in that section. By multiplication he will then be able to estimate the tonnage per hectare and ultimately the tonnage for the given field. To achieve an accurate estimate the farmer will do these exercises a number of times throughout different sections of the field.

The Afrikaans saying goes: ‘Om te meet is om te weet’, ‘to measure is to know’. We do yield estimates to know what potentially will be coming into the silos for the season. This allows us to plan for the season to come. In farming we always need to be thinking ahead and planning for different scenarios that may come our way. We do business in a volatile and unpredictable environment which is why we need to be continually planning for varied outcomes and by knowing what our harvest could be can help you do this more effectively.

Publication: May 2020

Section: Pula/Imvula