Experiments on effect of dripper discharge on cotton-root distribution

The relationship between soil wetting pattern and crop-root distribution is the theoretical basis for choosing soil wetted percentage, and the soil wetting pattern is directly subject to the dripper discharge. Therefore, the relation between dripper discharge and crop-root distribution is the basis for determining technique parameters of drip irrigation. Based on the pot culture experiments, cotton root structure and distribution were measured in seedling stage, bud stage, flowering stage, boll stage, and boll opening stage with the dripper discharge of 0.5, 1, 1.5, 2, 2.5 L/h. The experiments results indicated that the smaller dripper discharge resulted in narrow and deep distribution of cotton root in soil and compact root structure, while the larger dripper discharge led to wide and shallow distribution of cotton root in soil and sparse root structure. Cotton root-length density increased firstly and then decreased with the increasing of soil depth, and the maximal ratio of the root length in soil laid to the total root length in soil was observed in shallow soil as a result of the dripper discharge increasing. Similarly, the cotton root-length density reduced gradually from the root axis to both sides of it, and the maximal length density of root was observed at the position of root axis in soil and was diminished by increased dripper discharge. The results provide references for the selection of soil wetted percentage and dripper discharge in the process of drip irrigation’s technique design.