Crop Yield: Definition & Consequences

Instructor: Danielle Haak

Danielle has a PhD in Natural Resource Sciences and a MSc in Biological Sciences

Crop yield is the measure of crop produced per area of land. It's an important metric to understand because it helps us understand food security and also explains why your tomatoes can cost more one year and then less the following year.

What Is Crop Yield?

As the human population soars well beyond 7 billion people, so does the demand for food. That's a lot of mouths to feed! In addition to feeding humans, we also need plant-based crops to feed livestock and use for bio-energy.

One of the metrics used to determine the efficiency of food production is crop yield. Simply put, crop yield is the amount of crop harvested per area of land. Typically, it is used in reference to corn, cereals, grains, or legumes, and it may be reported in kilograms/hectare or metric tons/hectare. Sometimes crop yield is referred to as 'agricultural output'.

Estimating Crop Yield

Let's look at an example. Farmer Smith has 500 hectares of land he grows corn on, and he wants to estimate his crop yield. The easiest way to do this is to select a sample plot, harvest the corn, weigh it, and extrapolate that value to the rest of the land. So let's say he selects a 1 square hectare plot. Farmer Smith harvests and weighs his corn and discovers that he has 50 kilograms of product he can sell (50 kilograms per hectare). To extrapolate that to the rest of his land, he multiplies 50 kilograms by 500 hectares, yielding a total of 25,000 kilograms of corn! This is roughly how much corn he can expect to sell that season.

When estimating crop yield, it's important to remember that there will be fluctuations throughout the field based on the presence of microclimates. Different parts of the field may receive more nutrients, water, or sunlight, or the soil might be more fertile. To account for these variations, an average value (like 50 kilograms per hectare) is used.

Why Is Crop Yield Important?

There are a few reasons why understanding crop yield is so important. First, as we mentioned earlier, there are a lot of mouths to feed on our planet and there's a finite amount of land to grow food on. Being able to estimate crop yield allows us to understand food security, the ability to produce enough food to meet human needs in the foreseeable future.

Second, each crop has an estimate of what its yield will be, called a potential yield. Individual farmers can compare their crop yields to this potential yield to see how well they are competing. The difference between their output and the potential yield is called a yield gap, and a farmer's goal is to exceed the potential yield for the lowest price.

Why do farmers care about achieving the potential yield? Well, farmers' incomes are based upon the amount of food they produce. They don't get paid by the hour like some of us! Thus, if a farmer's crop yield is high, he (or she) is making more money! A farmer is always balancing the price of growing crops with the expected yield so that he makes as much money as possible.

Finally, we care about crop yields because they directly affect how much money we pay for groceries. If crop yields for strawberries are high one season, there will be a lot of strawberries for sale, so the price will generally be lower. If, however, conditions cause a dramatic decrease in the strawberry crop yield the following year, there will be fewer strawberries for sale, and they will be priced much higher. Additionally, if a crop has many years of low crop yield, farmers may switch to growing something else, causing a long-term decrease in availability and higher prices.

The government has a strong interest in helping farmers achieve high crop yields, as seen in this advertisement from around 1918.
crop yield announcement

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