By Jason Clark
Soil testing with extracting solutions for available nutrients has been the standard for determining nutrient availability since the 1950’s. The soil testing approach is based on identifying a critical value that separates a soil test response into zones that are deficient and sufficient. Since creating the South Dakota P recommendations (over 20 years ago) the adoption of no-tillage has increased, soil organic matter content has increased, and corn yields have steadily climbed.
These shifts in genetic, climatic conditions, and management practices likely changed soil processes that impact the dynamics of plant-available P in the soil. For example, using no-till compared to conventional tillage can increase total P in soils (Essington & Howard, 2000). Including cover crops causes changes in the soil organic matter (SOM) fraction of the soil, which has a large pool of soil P (Torbert et al., 1996). Cover crops can immobilize P while they are growing that is later released as the cover crop decomposes (Bünemann, 2015). Further, cover cropping has been associated with increases in mycorrhizal fungi that aid with plant uptake of P (Hallama et al., 2019).
Source : sdstate.edu