If you get arable lands for sampling near the tram line in which agriculture is regularly practised and is in no way disturbed by other anthropogenic activities, you can collect samples. Most important is that your research design should be in the tune of your research objectives.
Interesting question! It is generally not advisable to sample in the transit area. Anyway we must be clear about the objectives for which the sampling is done. If you want to evaluate is the nutrient content and availability of those for crop growth, which grows in different conditions of the sampling site conditions, should not be done in that area sampling. If the crop grows indifferently in busy area by machinery and traffic free zones, you must take samples including both areas. Bear in mind also that which passes machinery soil is compacted, so the thickness of soil sampling will be different.
If you get arable lands for sampling near the tram line in which agriculture is regularly practised and is in no way disturbed by other anthropogenic activities, you can collect samples. Most important is that your research design should be in the tune of your research objectives.
It depends on the objective of sampling. If you are measuring any physical parameters, then you cannot take sample from tram line. Otherwise you can collect.
Any soil site , where we intend to study crop response , soil sampling is must do exercise ..even when you are willing to evaluate the bearing strength of soil , you need do to sampling , off course procedure for the same will be different .