A comparison of soil core sampling and minirhizotrons to quantify root development of field-grown potatoes

Abstract

Root growth of potato (Solanum tuberosum L.) is sensitive to soil conditions. A reduced root system size can result in reduced uptake of water and/or nutrients, leading to impaired crop growth. To understand the mechanisms by which soil conditions affect crop growth, study of temporal and spatial development of roots is required. In field experiments, effects of soil temperature, soil compaction and potato cyst nematodes (Globodera pallida) on root growth of potato cultivars were studied using two methods: core sampling and vertically oriented minirhizotrons. Minirhizotrons showed relatively more roots in deeper soil layers than core sampling, probably because of preferential root growth along the tube. Spatial distribution of roots should therefore be analysed by core sampling. To eliminate differences in spatial distribution, total root systems as measured by both methods were compared. Nematodes, cultivars and time did not affect the relationship between both methods. Soil compaction, however, affected it because of a strong response of root length in bulk soil and small differences in root number against the minirhizotron, suggesting that soil coring has to be used to study effects of different bulk densities. With both methods, sequential measurements of roots give the net effect of root growth and decay. Data on root turnover can only be obtained with minirhizotrons by comparing video recordings of different dates. Other information obtained with minirhizotrons is the average orientation of roots. Moreover, the minirhizotron method has the advantage of demanding less labour.