Root methods for intercropping

A sustainable way to enhance overall food production is to increase the exploitation of subsoil resources with deep roots. In this regard, intercropping is highly recommended to maintain agricultural systems, because it can increase the soil exploitation, especially when using deep-rooted crops. Various root measurement techniques help to understand the importance of roots and their role in intercropping. In this work, there are two main objectives: (i) to study methods that enable the distinction of roots and root function of plant species grown in mixed cropping; and (ii) to investigate the root interaction and resource competition in intercropping systems. The methods used for distinguishing roots and root function in intercropping systems were qPCR, amplicon sequencing, 15N tracer uptake, and anatomical techniques. Experiments were conducted to study the root competition between legume and non-legume mixtures under semi-field conditions, and various stands of mixed crops in strip intercropping in the field. The root studies were conducted by direct visual distinction in rhizotron tubes, by determining uptake of labeled nitrogen, and by root excavation followed by different analyses. It is concluded that several methods can be used to distinguish roots from different species in intercropping systems. By the use of the DNA-based methods, qPCR and amplicon sequencing, it was possible to quantify root fractions from root mixtures in intercropping. Root activity of individual species of crops in the mixtures could also be detected by 15N tracer uptake. Additionally, microscopy with a suitable staining method further allowed reliable differentiation among species by studying differences in root anatomy. Finally, the use of red-colored roots also allowed for differentiation between two species grown in intercropping systems, observed via direct visual observations and by using root imaging techniques. The observations on belowground interactions in strip intercropping of different crop species in this study could be useful as a guidance and to provide profound understanding about the mechanisms that are responsible for the yield advantages of intercropping systems, crop design, and optimization of agronomic choices in intercropping systems.