Question: In what field do biochemists examine soil and fertilizer?
About the article "Biochemistry", section "Abstract".

Candidate passages:
Biochemists are scientists trained in biochemistry.
Typical biochemists study chemical processes and chemical transformations in living organisms, other biochemists study DNAs, proteins and cell parts.
The word "biochemist" is a portmanteau of "biological chemist".
Biochemists also research how certain chemical reactions happen in cells and tissues and observe and record the effects of products as in food additives and medicines.
The main function of a biochemist is to focus on improving the qualities of lives.
Biochemist researchers focus on planning and conducting research experiments, mainly for developing new products, updating existing products and analyzing said products.
It is also the responsibility of a biochemist to present their research findings and create grant proposals to obtain funds for future research.
Role Biochemists study aspects of the immune system, the expressions of genes, isolating, analyzing, and synthesizing different products, mutations that lead to cancers, and manage laboratory teams and monitor laboratory work.
Biochemists also have to have the capabilities of designing and building laboratory equipment and devise new methods of producing correct results for products.
The most common industry role is the development of biochemical products and processes.
Identifying substances' chemical and physical properties in biological systems is of great importance, and can be carried out by doing various types of analysis.
Biochemists must also prepare technical reports after collecting, analyzing and summarizing the information and trends found.
In biochemistry, researchers often break down complicated biological systems into their component parts.
They study the effects of foods, drugs, allergens and other substances on living tissues; they research molecular biology, the study of life at the molecular level and the study of genes and gene expression; and they study chemical reactions in metabolism, growth, reproduction, and heredity, and apply techniques drawn from biotechnology and genetic engineering to help them in their research.
About 75% work in either basic or applied research; those in applied research take basic research and employ it for the benefit of medicine, agriculture, veterinary science, environmental science, and manufacturing.
Each of these fields allows specialization; for example, clinical biochemists can work in hospital laboratories to understand and treat diseases, and industrial biochemists can be involved in analytical research work, such as checking the purity of food and beverages.
Biochemists in the field of agriculture research the interactions between herbicides with plants.
They examine the relationships of compounds, determining their ability to inhibit growth, and evaluate the toxicological effects surrounding life.
Biochemists also prepare pharmaceutical compounds for commercial distribution. 
Soil acidification.
Nitrogen-containing inorganic and organic fertilizers can cause soil acidification when added.
This may lead to decreases in nutrient availability which may be offset by liming. 
The soil on headlands is subject to greater levels of soil compaction because it receives more traffic per unit of area than the field as a whole.
Yields are generally lower than in the field itself due to additional implement traffic and crop damage from implements turning on them as well as compaction.
Soil fertility levels are frequently higher than in the main part of the field due to overlapping applications of fertilizer coupled with reduced yields. 
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 dependency.
Effectively farmers unknowingly became 100% dependent on 'bought in' water soluble, inorganic fertilizers since the sterilization of soil microflora including its mycorrhiza, reduced the availability of other natural and trace minerals within the soil.
This to some extent explains the resurgence of interest in organic and particularly 'biodynamic' farming systems since these systems replace the soil organisms essential to converting soil minerals into plant available (but rarely water soluble) nutrients.
They do this by a variety of processes including chelation whereby essential minerals become plant available - as measured by weak citric acid extraction techniques.
Hence the citric acid solubility of phosphate rocks has emerged as a measure of plant availability and enabled so-called 'reactive' phosphate rocks to be used as fertilizer minerals.
These should not be confused with high fluorine apatite rocks in which the fluoride content performs a similar function to its role in hardening teeth enamel, i.e.
immobilizing phosphorus.
This explains the oceanic origins of many of these high fluorine rocks (Christmas Island, Ocean Island) since the fluorine absorbed from the sea has prevented what were originally massive deposits of bird guano - from being leached from the coral based limestone rocks on which they were originally deposited.