Modification of the RZWQM2-P model to simulate labile and total phosphorus in an irrigated and manure-amended cropland soil

Authors: PAN, PENG - McGill University - Canada; QI, ZHIMING - McGill University - Canada; Koehn, Anita; Leytem, April; Bjorneberg, David - Dave; Ma, Liwang

Submitted to: Computers and Electronics in Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/15/2022
Publication Date: 2/7/2023
Citation: Pan, P., Qi, Z., Koehn, A.C., Leytem, A.B., Bjorneberg, D.L., Ma, L. 2023. Modification of the RZWQM2-P model to simulate labile and total phosphorus in an irrigated and manure-amended cropland soil. Computers and Electronics in Agriculture. 206. Article 107672. https://doi.org/10.1016/j.compag.2023.107672.
DOI: https://doi.org/10.1016/j.compag.2023.107672

Interpretive Summary: Phosphorus is an essential crop nutrient that can impair water quality if it leaves agricultural fields. Long-term application of manure can increase soil phosphorus beyond what is needed by crops. The Root Zone Water Quality Model was recently updated to simulate phosphorus pools in soil (RZWQM2-P). This study modified the phosphorus module to account for changes in total soil phosphorus. The model was evaluated using a dataset from an irrigated field study that included a fertilizer treatment and six rates of dairy manure. Simulated amounts of phosphorus in the soil and removed by crops matched measured values from the field study. Long-term simulation results showed that it took 14 years for soil phosphorus concentrations to return to the initial values after dairy manure was applied for eight years. The modified RZWQM2-P model can be used to simulate soil phosphorus and to assess phosphorus management practices in irrigated cropland amended with manure.

Technical Abstract: With the expansion of the dairy industry, phosphorus (P)-enriched dairy manure has increasingly been used to replace chemical fertilizer to meet crop nutrient demand. This practice could lead to excessive total P accumulation in the soil and increase the risk of P pollution in the environment. The newly-developed RZWQM2-P model uses the soil P pool structure from the EPIC model, which is not sensitive to total soil P. Therefore, we modified the P module in RZWQM2-P to increase its sensitivity to total soil P. We subsequently assessed the ability of the modified model to simulate labile soil P, total soil P, plant P uptake, and crop yield using a dataset collected from an irrigated field treated with dairy manure and inorganic fertilizer at eight rates. We simulated the long-term soil P dynamics under three P-application scenarios. The results suggested that the modified RZWQM2-P model simulated field-measured annual total soil P, plant P uptake, and crop yield well. Labile soil P was simulated less accurately, but the results were acceptable as the model responded well to P treatments. Long-term simulation results showed that it took 14 years for the labile soil P level to return to the initial level after eight years of manure-P applications at a rate of 65.5 kg P/ha/year. The modified RZWQM2-P model can be used to simulate total soil P and labile soil P contents and to assess P management practices in irrigated cropland amended with manure.