Impact of fertilizer and cropping management practices on phosphorus recovery in crop and soil, and associated losses in runoff water in variable topographies of Saskatchewan
Date
2025-03-20
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
ORCID
0009-0003-1468-5696
Type
Thesis
Degree Level
Doctoral
Abstract
Those seeking to effectively manage the fate of phosphorus (P) in the environment must resolve an apparent dichotomy where P may be supplied to growing crops in the form of P fertilizer due to an insufficient supply from soil, but is also a pollutant when surface water bodies receive runoff water enriched in bioavailable P. Across the Canadian Prairie Pothole Region (PPR), P is predominantly transported in the environment in the dissolved form during the spring snowmelt. Losses of P supplied to agricultural fields may be exacerbated when P is applied to seasonally-flooded depressions and lower slopes commonly found in the PPR, especially those which have been drained. However, the degree to which implementation of 4R P Stewardship and other cropping management practices can mitigate P losses in snowmelt runoff water from landscapes of variable topography is largely unknown, and few previous investigations have considered the impact that fertilizer sources of different solubility have on both promoting crop P nutrition and reducing P losses in water. Further, while others have investigated the influence of landscape position and associated slope on nutrient transport in rainfall runoff, its importance in influencing nutrient transport in snowmelt runoff is less well understood. Therefore, this work evaluates agronomic and environmental performance of combinations of 4R fertilizer and cropping management practices across varying landform elements representative of the hummocky terrain of the Canadian PPR. Sites used for the research included upper and lower slope positions of a farm field located in knob and kettle topography in the Brown soil zone near Central Butte, SK, and level slopes and drained basins in gently undulating topography in the Dark Brown soil zone at Discovery Farm near Langham, SK.
This work demonstrated that the plant-availability and mobility of P in runoff varied according to the P fertilizer source applied and the chemical properties of the receiving soil. Fertilizer P forms of lower solubility like struvite and rock phosphate sometimes showed lower plant availability of P and yield response, but also resulted in lower losses of P in simulated snowmelt runoff. Notably, soil moisture conditions interacted with the relative solubility of the applied P fertilizer to influence its agronomic and environmental performance. In contrast to its major influence on rainfall runoff losses, slope did not appear to influence soluble P losses in snowmelt runoff, with the muted influence attributed to lower overall energetics of snowmelt relative to rainfall runoff. The performance of fertilizer and cropping management practices implemented to drained agricultural basins was tied to the rate of P fertilizer applied, where variable rate practices that applied reduced rates of P fertilizer in the basins were most effective in lowering soluble P concentrations in snowmelt runoff. However, total P load was driven by the total runoff volume exiting the drained basin during spring snowmelt. Collectively, these findings improve our understanding of the factors that control nutrient transport from agricultural fields in the Canadian PPR and their relative importance. Findings from this work support the site-specific prescription of beneficial management practices intended to maximize crop utilization of applied and residual P, while limiting P losses in snowmelt runoff.
Description
Keywords
Phosphorus, Snowmelt runoff, P use efficiency.
Citation
Degree
Doctor of Philosophy (Ph.D.)
Department
Soil Science
Program
Soil Science