An improved understanding of phosphorus dynamics and fertility management in forage production systems
Lamichhane, P. 2024.
Abstract
Forage fertility recommendations have not changed since the 1980s, and
anecdotal evidence suggests producers often apply less than provincially recommended
rates. A better understanding of forage fertility, especially phosphorus (P), is crucial to
optimize profit and reduce environmental nutrient losses. This thesis explores how
forage fertility affects productivity in two scenarios. First, a 14-week controlled
environment study with Italian ryegrass (Lolium multiflorum) tested crop response to P
addition in soils with different soil organic carbon (SOC) and agriculture land use
histories. Crop yield was influenced by soil type and P supply rate (determined using
anion exchange probes), but not by soil test P (Olsen P), suggesting SOC and
phosphatase activities also impact P supply. In addition, a three-year field trial
compared provincial soil test recommendations with light nutrient application (112 kg ha
-1 of 19-19-19 NPK fertilizer) across 19 forage types. Profitability increased with
fertilization only in mixed grass-legume stands due to high nitrogen costs for grass-only
stands. The overall findings highlight the importance of soil properties (e.g., SOC,
enzymatic activity) and soil testing in increasing fertilizer use efficiency.
