The role of hydraulic lift and subsoil P placement in P uptake of cotton (Gossypium hirsutum L.)

Hydraulic lift can be a desirable characteristic for cotton growing in areas that experience frequent drying of the topsoil. This study employed specialized soil columns to test if cotton can hydraulically lift water and whether this hydraulically lifted water can facilitate P acquisition from the dry topsoil of a clay and a sandy soil. The role of subsoil P placement on cotton growth was also tested. By using a Theta probe, hydraulic lift was detected in the clay soil for 7 days after water was withheld from the topsoil. However, in the sandy soil, a significant overnight increase in soil water was only detected for one day for the treatment with subsoil P application. Where P was applied to the topsoil, and water was withheld, cotton roots showed significant root P uptake from the sandy soil, but negligible P uptake from the clay soil. Irrespective of topsoil watering, the higher root length density in the subsoil of the clay soil accounted for the pronounced response to deep P placement. This study demonstrated that soil texture affects the amount and longevity of hydraulic lift from cotton roots. Hydraulic lift detected in the clay soil did not aid P acquisition from dry surface soil by cotton plants.