Triple super phosphate impact on maize transpiration and root hydraulic conductance on drying soils collected from six locations in the United States

Abstract

Background and aims: Previously, triple super phosphate (TSP) application to one soil type was unexpectedly found to cause with soil drying an initiation of linear decrease in maize transpiration rate at an unusually high soil water content. The resulting overall slower soil water extraction resulted in crop drought resilience. A key issue is whether the response occurs with drying of other soils. The objective of this study was to document for six soils collected from US maize production areas their transpiration response on drying soil to TSP and their root hydraulic conductance. Methods: Maize plants were grown in pots on soil treated with either TSP or diammonium phosphate (DAP) and soil pH of 5.4 or 6.5. Data from daily pot weighing over a 10–14 dry-down period were used to determine soil water content at initiation of transpiration decrease. A second set of experiments determined root hydraulic conductance of well-irrigated plants grown on these six soils. Results: The initiation of transpiration decrease occurred at an unusually high soil water content for five of the six soils at pH 6.5 treated with TSP. Root hydraulic conductance was substantially decreased for plants on all six soils treated with TSP and pH 6.5. Conclusion: Results were consistent with the previous observation that transpiration decrease with TSP soil application was initiated at an unusually high soil water content, which was indicative of increased crop drought resilience. The TSP-induced transpiration sensitivity to soil drying appeared to be linked to an observed decrease in root hydraulic conductance.