Framework for Cumulative Final Exam - FOR 345 / 545
December 2011
The Cumulative Final Exam – Review session will be Friday 9 Dec. at 9:30 am
Part I – Prequel : Loose ends – Nutrition
1. Nitrogen Cycle - components, transfers among components, C/N ratio
2. Phosphorus
Problems: low total amount, availability, fixation; eutrophication
Availability (phosphate anions vs. soil pH, clay, OM, Fe, Al, Mn, Ca)
Fixation of added P fertilizer
Role (& classification) of mycorrhizae
Part II –Sequel. You may bring a SINGLE page of notes (back and front) to the final exam. No
Calculators.
My purpose in having a cumulative final is twofold: 1. to show you the tremendous amount of
material learned; and 2. to provide you with an opportunity to integrate the material, which was
presented as a series of sequential topics successively building during the semester.
The course began with the concept of the soil as a biogeochemical membrane, and concluded
with the topic of plant nutrition. We have studied the soil system from a biological perspective,
considering the impacts of soil physical and chemical properties on biological productivity. The
foundation of this approach is an understanding of how biological productivity is constrained by
the quantity and quality of root exploitable soil volume.
Parent materials vary in composition due to mode of deposition and rock/mineral composition.
Soil texture and mineralogy set the stage. Recall the marked differences in texture among the
various parent materials (e.g., lacustrine, till, colluvium, outwash, etc.). The quality of that material
is influenced by elemental composition of primary and secondary minerals of which the parent
material is comprised. Soil texture influences soil organic matter, which has a profound impact on
soil structure, bulk density, total pore space, and pore size distribution. Landscape position
combined with soil physical properties influence movement and storage of water captured by
drainage class. This, in turn, influences soil aeration, and temperature, strongly affecting
biological productivity. In addition, these influence erosion potential and response of the soil
system to management.
With that foundation, we explored soil chemical properties: CEC, soil acidity, and the concept
of soil as a buffer. The course culminated with plant nutrition, focusing with greater depth on the
essential elements. Given adequate physical properties, the capacity of the soil to provide
nutrients depends on soil colloids and the capacity to cycle nutrients through decomposition of
organic matter and mineralization (recall the N cycle and our model of plant nutrient availability).
The soil system can be managed to improve biological productivity if the factors that constrain
productivity can be identified (e.g., physical – limited volume, excessive or insufficient moisture,
excessive coarse fragments, chemical - nutrient limitations).
Thought for the day (or the weekend as you power study) - Yesterday is history, tomorrow is
mystery, and TODAY is a gift - that’s why we call it the present. Good luck in your preparations for
the end of the semester.