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Nyamaizi, Sylvia

University of British Columbia

Soil phosphorus (P) has reached environmentally concerning levels in the Fraser Valley, one of the most intensively farmed areas of British Columbia (BC), due to the repeated, excess application of P as manure and mineral fertilizers. To help address the potential risk of P losses to aquatic ecosystems, it is crucial to account for both crop production and environmental protection objectives. In this dissertation, I aimed to develop strategies and tools to improve P management and monitor environmental P risks associated with agricultural land with high soil test P (STP) in the Fraser Valley. Two-year field trials were established in eight sites in 2020 and 2021 to investigate the effects of increasing starter P rates on silage corn growth and phosphate availability during the growing season. Results showed that starter fertilizer P, at any application rate, in high-P manured soils does not improve silage corn yield; farmers applying manure at ploughing in soils with high P concentrations can reduce or eliminate starter fertilizer P without impacting silage corn yields, decreasing the reliance on off-farm P inputs and reducing potential P loss to the environment. This research also investigated how increasing soil pH with lime could affect agri-environmental P risk indicators and P sorption characteristics. Increasing soil pH with lime did not affect the degree of P saturation (DPS), and P saturation index (PSI) but showed decreasing trends of Mehlich-3 extractable P and water extractable P (Pw) concentrations even though the extent was only significant for Pw in soils with initial pH = 5.8, indicating a reduced risk of P loss when soils are limed. I used the results of these two studies to develop a tool for monitoring environmental P risk by identifying four specific environmental P risk classes, namely low, moderate, high, and very high with the moderate PSI and Pw limits = 6.6-10.8% and 2.2-4.1 mg kg⁻¹, respectively. This dissertation contributes to our understanding and application of P risk indicators to quantify and monitor the risk of P loss to improve fertilizer and manure management in high P-affected areas of the Fraser Valley.

Text

2024-03-18

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/87593

Soil Science

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/