Spatial distribution and dynamics of cotton fine root under film-mulched drip irrigation

Fine roots distribution and dynamics (production, mortality, and longevity) significantly impact the crop soil ecosystems. However, the spatial distribution and dynamics of cotton (Gossypium hirsutum L.) fine roots under film-mulched drip irrigation are poorly understood. The present study aims to characterize these distributions and dynamics measured using a minirhizotron technique and the influence of soil conditions. The non-uniform distribution of soil moisture and salinity may lead to the differences of root length density (RLD) distribution. A clear decreased trend for the average RLD was observed in the shallow soil layer due to high localized salinity accumulated after brackish water irrigation. There existed a clear high soil moisture content strip at depth which may lead to a high RLD peak in the 95–100 cm soil layer. Average live root production was characterized by a very high rate during the initial growth stage followed by a decline after budding, which in turn was followed by a slight increase during boll opening. The average number of new roots was highest during the initial growth stages, decreasing after the budding stage. Thinner roots in the deep soil had shorter lifespans than those in shallow soil. Our study indicated that the minirhizotron technique can be used reliably as an in situ, non-destructive method for estimating cotton fine roots distribution and dynamics under film-mulched drip irrigation. To evaluate cotton fine root distribution and dynamics under film-mulched drip irrigation more accurately, a cotton root system architecture model could be parameterized in space and time based on the minirhizotron observations. •A region of increased soil moisture at depth may led to a high RLD peak at 95–100 cm soil layer.•Average number of new roots were highest during initial growth stages while decreasing after budding.•Thinner roots in the deep soil had shorter lifespan than those in shallow soil.•A cotton root system architecture model should be further parameterized in space and time based on the minirhizotron data.