Roots: The Basis for Production

A good root system is critical to the final yield of any crop, including vegetables. Irrigation and fertigation may deliver right to the plant all the inputs needed but roots still do more than just anchor the plant. Roots help to store carbohydrates and the water and nutrient absorption and transport.

Many vegetable crops start out as seedlings with a basic tap root and as they grow continue to develop lateral roots and finer roots. Under good soil conditions these lateral roots should head off into the soil at about a 30 degree angle from the plant. If you see roots making a ninety degree angle, there has been some sort of barrier like soil compaction that has prevented the plant root from developing normally. It is critical to keep these lateral roots healthy, they are responsible for 90 % of the water and nutrient uptake after the seedling stage is complete.

Irrigation and fertigation can improve crop yields through more efficient delivery to the plant. It can also help to support plants with a reduced root system but actively growing root tips are still needed for efficient nutrient and water uptake. As the root matures, the root surface becomes less permeable and the root hairs die and decay. Actively growing root tips have root hairs, as many as 2500 hairs per square cm. This increases the absorptive surface of the root 1.5 to 20 times that of the original young root. Fine roots are constantly growing and dying on healthy plants with a turn over time of about 14 days. Stress like excess water or the opposite, dry soil can slow the development of new fine roots. When conditions change, a healthy plant can respond with new fine roots within 24 hours.

Most crops have the greatest root mass during their reproductive stage, for most vegetable crops that would be during harvest. That makes it a great time to look at roots. A walk with a shovel and a quick shake of the root ball can give you some insight into how the crop has viewed soil conditions in 2008. If you want to get fancy you can wash the roots but a quick shake will remove most of the soil and allow you to see the larger root structures.

Look at root colour. Roots should be white to a creamy colour if they are healthy. Look at the overall root ball. Compaction or layers that interfere with root development will appear as areas with few roots or flat roots or even thickened, almost nubby root ends. Take a look at the overall structure of the roots, does it look like it has explored the soil evenly? Or are there areas where there are few roots or lateral roots. Consider the soil conditions and the possible cause.

Take the time to dig up some good roots to better evaluate the poor roots. Now as summer fades into fall is a great time to get to the roots of your crop!

The yellow line marks out an area of flattened root where the corn root hit a solid surface too hard for it to penetrate