Methods of root investigation in the field


An interview with Professor Vamerali of the University of Padova, Italy.

Basel, Switzerland
April 15, 2014


Professor Vamerali

Professor Teofilo Vamerali is Associate Professor in Crop Science, Department of Agronomy, Food, Natural Resources, Animals and the Environment, University of Padova, Italy. He has studied roots since starting his Ph.D. in 1993. His field of expertise focuses on soil quality and its impact on plants and the improvement of suboptimal soils (water, PH, heavy metals), as well as crop modelling and crop production. Professor Vamerali has contributed to several books on root measurements and methods. We spoke with Professor Vamerali to learn more about his experiences working with roots.

Video interview with Professor Vamerali


Why did you start studying root architecture?

When I started my Ph.D., studying roots was a new field of work. I was asked to participate in a collaboration to write a handbook on methods for the characterization of roots. After my Ph.D., we had the opportunity to continue this work on different crops. Our focus was on the differences in behavior of their root systems, as well as the effect of different agronomic management practices, such as tillage, fertilization or irrigation, on root growth. Later, we also included the effect of pests like nematodes and contaminants (e.g. heavy metals).


Why is it important to be able to characterize roots and understand root growth?

Crop growth and production is strictly connected with the ability of plants to colonize soil and recover water and mineral nutrients through their roots. Roots also positively interact with N-fixing and endophytic bacteria, as well as with mycorrhizal fungi, which can help crop establishment. Indeed, root behavior within soil heterogeneity is still difficult to predict due to multiple interactions with soil, climatic conditions, pest and disease, and agronomic management. In the last years, awareness of the importance of studying roots has been increasing within the research community, although we have still to improve the methodological approach. In many investigations, we did not highlight yield improvements as consequence of improved root growth, but yield losses were always associated with smaller root systems.


How do you select a specific tool to study roots and root growth?

The choice of the method is an important issue in root investigations. It depends on the reason you are studying roots and the problem you want to solve.


Many people are interested in studying diseases and pests (insects/ nematodes) that attack the roots. In other cases, people are interested in the behavior of roots in relation to fertilization, tillage or the depth of the soil, climate change, pollution of the soil, etc. It also depends on the crop and its architecture. You have to choose the method according to the aim of your research.


We use different methods in different crops because the situations are very different. And we are interested in particular to study roots in the field, not in the lab. Of course, there is also another factor that has an impact on the type of study that you should use and that is: how much money you have available to do your research.


What methods have you used to analyze roots?

We started with very old fashioned methods in the beginning, like the intersect method. For that we took soil samples. After washing the soil particles away, we measured the roots by counting intersects manually over a grid. These days, we are obviously using software that allows us to retrieve important traits with great accuracy, like root length, the surface, the diameter, the number of branches or the number of tips.


We also moved to mini-rhizotrons because soil sampling is a destructive method of investigation. With mini-rhizotrons, you are able to study the growth of a single root at any time you want by using a small camera that is placed next to the plant in a transparent tube. In this way, you are able to follow the formation, the growth of a root and finally the point in time when it is dying. You are also able to follow the rate of root renewal by the plant. There are also some indirect methods of investigation. In particular, we use the electrical capacity method. When using this method, you connect a pin in the soil and another pin at the stem base of the plant and measure the electrical capacity of this system. By measuring the electrical capacity you receive, an indirect estimation of the roots that are in contact with the water of the soil.


What impact does the rate of root renewal have on the plant?

Root renewal is a natural process of both perennial and annual plant species that maximizes the efficiency of carbohydrate use within plants and improves the recovery of soil resources. Young roots have the maximum uptake capability, while aging reduces their efficiency. When respiration costs – instead of benefits – of a root tend to prevail, the root eventually dies in most cases, especially in adverse soil conditions. In some crops, 66 days is the threshold for maintaining a root alive. Root turnover is also an interesting process for enriching soil with organic matter and maintaining a useful microbial activity in the rhyzosphere.


Books to which Professor Vamerali has contributed:

Root Methods, A Handbook

Smit, A.L., Bengough, A.G., Engels, C., Noordwijk, M. van, Pellerin, S., Geijn, S.C. van de (Eds.), 2000

Measuring Roots – an updated approach

Mancuso, Stefano (Ed.), 2012



Prof. Vamerali was interviewed by Dr. Melanie Goll, Technical Innovation Manager, Syngenta. Melanie holds a Ph.D. in plant pathology and focuses on seed treatment development, especially fungicides and nematicides.