Crop breeding

Why do we need to know harvest yield during crop growth?

When it comes to crop yield, most of us are concerned with what it will look like at harvest time. How many kilograms of a harvest can we expect – and when. For those growing crops above ground, there are certain things they can look for to predict the yield. Number and quality of flowers, size of stalks, etc., help predict the yield of many crops.

But for tuber crops this is tricky. The part that is harvested is underground. This includes cassava*, yams, and potatoes. Looking for predictors of yield is difficult.

Four men holding large and long, tan, tuber crops called cassava in a field
Cassava is a tuber crop and is a staple food in Africa and South Asia. Estimating the yield of underground crops is difficult, so researchers are looking to ground penetrating radar to help. Credit: Colin Khoury

Cassava is one of the most drought-tolerant crops in the world. This hearty plant can grow on marginal lands where other crops would die. It is currently a staple food source for millions of people in Africa and South America, serving as a major source of carbohydrates.

Because it is drought tolerant, cassava is an essential crop for parts of the world that will be most affected by climate change. This is why it is urgent that we work to find cassava varieties that mature more quickly. This will reduce the time to harvest, and potentially increase a farmer’s profitability and sustainability.

To help us predict the yield of cassava, some researchers are using technology that will allow us to ‘see’ underground. Ground penetrating radar (GPR) technology is quick, inexpensive, and non-destructive to the crop while taking measurements. It operates like the metal detectors we take to the beach to search for treasures. Researchers drag or hover the instrument over a surface in order to detect information on what is beneath.

Researchers scanning a cassava field with ground penetrating radar at CIAT, Columbia. Courtesy CIAT.

Ground penetrating radar detects changes in subsurface materials – in this case, when the radar bounces off the surface of the cassava tuber. We can also determine the size of the tuber based on the information collected.  Tuber crops such as cassava are the ideal crop for this task because the tubers are very distinct from the soil. The soil has pores filled with air and water, whereas cassava is a very solid tuber, like potatoes.

For crops such as cassava, which are a staple in food-insecure regions, decreasing the growth cycle is vital. Cassava, however, is a tuber crop for which the consumable part is underground. Thus, new technologies for non-destructive monitoring of yield during the growing cycle are on the way.

Answered by Iliyana Dobreva, Texas A&M

*For those not familiar with cassava, it is a root/tuber crop. A product you might be more familiar with – called tapioca – is extracted from the cassava tuber.

About us: This blog is sponsored and written by members of the American Society of Agronomy and Crop Science Society of America. Our members are researchers and trained, certified, professionals in the areas of growing our world’s food supply while protecting our environment. We work at universities, government research facilities, and private businesses across the United States and the world.

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