Oct 2, 2024
Vegetable Crop Root Systems (2024)
When going into the field to evaluate a crop, there are typically three fundamental points we need to take into consideration that include: 1) stage of growth, 2) general crop vigor and yield potential, and 3) anticipate the next stage of development and what we need to do in terms of field crop management. These considerations are commonly focused on aboveground crop evaluations. The root system is also an important part of the crop condition to evaluate but we commonly do not evaluate roots because of the difficulty in doing so.
Root systems and early development were described in a basic manner in a recent article on 4 September (UA Vegetable IPM Newsletter Volume 15, No. 18).
The effective root zone depth is the depth of soil used by the bulk of the plant root system to explore a soil volume and obtain plant-available moisture and plant nutrients. Effective root depth is not the same as the maximum root zone depth. As a rule of thumb, we commonly consider that about 70% of the moisture and nutrient uptake by plant roots takes place in the top 24 inches of the root zone; about 20% from the third quarter; and about 10% from the soil in the deepest quarter of the root zone (Figure 1).
The small and very fine root hairs are the most physiologically active portion of a developing root system. It is important that plants continue to develop and generate fresh young roots and an abundance of fine root hairs to maintain water and nutrient uptake.
Figure 1. General pattern for plant-water and nutrient uptake from the soil profile.
Root development patterns are dependent on the nature of the soil profile in the field. Soil profiles with compaction layers, as well as rock, clay, or caliche layers can limit and alter root development and the full exploration of the soil volume that the plants are capable of (Figure 2). So, it is good to know what the soil profile looks like in the field and understand how that will impact plant root development.
Figure 2. Generalized soil profile with major horizons.
Leafy green vegetable crops need to develop a marketable plant in a relatively short amount of time and a strong root system is essential. Transplants are commonly being used in vegetable crop production systems and the transition of transplants to field conditions is a major step in the production process. The transition is primarily experienced by the plant below ground.
Transplanted crops will have altered root systems due to the constraints within the rooting cone. Further root development beyond the original cone rooting mass is important for crop success. Thus, it is important to monitor the root system transition and the relationship to overall plant development.
Checking root systems is a plant destructive process since we need to literally excavate the roots from the soil and it does take time and effort. Accordingly, it is also important to be careful of where and how we sample plants and evaluate the root systems in a field.
Crop species can vary significantly in their patterns of root development, and it is important to know what is “normal” when evaluating crops in the field. An excellent reference for vegetable crop root system development is a 1927 publication by Dr. John E. Weaver and William E. Bruner from the University of Nebraska (Root Development of Vegetable Crops). This publication can be found at the following link:
https://soilandhealth.org/wp-content/uploads/01aglibrary/010137veg.roots/010137toc.html
A few basic examples from the Weaver and Bruner publication are provided in the following figures (Figures 3-10).
Figure 3. Cauliflower, 3 weeks after transplanting
Figure 4. Cabbage roots, 55 days after transplanting.
Figure 5. Cabbage roots, 75 days after transplanting.
Figure 6. Pepper roots, 24 days.
Figure 7. Pepper roots, 45 days (6 weeks).
Figure 8. Pepper roots, mature.
Figure 9. Lettuce roots, 3 weeks. The roots on the right were grown in compact
soil, the roots on the left were grown in loose/open soil.
Figure 10. Lettuce roots, 60 days.
To contact Jeff Silvertooth go to:
silver@ag.arizona.edu