Spatial-temporal distribution patterns of cotton root system under brackish water mulched drip irrigation and three-dimensional dynamic growth simulation

ObjectiveXinjiang is located in the arid to semi-arid region of China, where water resource conservation is critical. Brackish water mulched drip irrigation technology is widely used for cotton cultivation in Xinjiang. However, improper use of brackish water may lead to soil salinization. Regions with high cotton root density (RLD) may experience strong water absorption, resulting in soil moisture reduction and excessive salt accumulation, and subsequent declines in cotton yield. To ensure the soil habitat and cotton yield under brackish water mulched drip irrigation, the influence of cotton root distribution on field water and salt transport should be fully considered. MethodsBased on the field experiments conducted at the cotton fields of the Irrigation Experiment Station of Water Conservancy Research Institute, Bayingolin Administration Bureau in Xinjiang, this study obtained cotton root growth parameters to construct a growth model for cotton roots under brackish water mulched drip irrigation, which quantitatively characterized the spatiotemporal distribution patterns of cotton roots. ResultsThe results indicated that the spatial distribution of roots was influenced by soil moisture and salinity. During the budding to flowering stage, roots are more concentrated in the drip irrigation belt and inter-row positions. From the peak flowering to boll-opening stage, roots showed obvious decline beyond a depth of 50 cm, but developed in the soil depths of 90-130 cm. The predicted trend of the three-dimensional growth model of cotton roots was consistent with the actual observations, with MRE (the mean relative error) ranging from 0.2486 to 0.5378, RMSE (the root mean square error) from 2.4127 to 4.8710 cm/cm2, and d (the index of agreement) from 0.7541 to 0.9529. The simulation results effectively described the distribution of cotton RLD. The three-dimensional simulation of cotton root system incorporates actual field planting conditions, achieving a dynamic three-dimensional growth effect. The model could effectively simulate the morphological structure and developmental processes of the root system. ConclusionBased on in-situ dynamic monitoring by minirhizotron technique, CPlantBox can be used to construct the cotton root growth model under brackish water film drip irrigation. The research results lay the foundation for exploring the impact mechanism of spatial-temporal distribution of root morphology on field soil water migration and root zone water and salt distribution, which has important theoretical and practical implications for improving high and stable cotton yield in Xinjiang.