Nitrogen as a Nutrient

By understanding the different chemical forms of Nitrogen, we can manage root-zone pH and avoid toxic buildup of ammonium.

Plants have the ability to take up several chemical forms of Nitrogen either you apply inorganic fertilizer or organic manure. The most common are: ammonium (NH4+), which has a positive charge and nitrate (NO3-), which has a negative charge. Many commercial fertilizer mixes contain a combination of all two nitrogen forms.
You can read more on this by reading following post. Pl click. NITROGEN AS A NUTRIENT

pH correction is a key strategy to manage fertility in soils with non-optimal pH

The acid or very acid condition of many tropical soils does not suit most commercial crops. Liming is therefore a prerequisite for most agricultural farm units. The relationship between acidity and base exchange characteristics in soils has to be fully understood.
Many crops require a pH of over 4.5 for optimum growth. A few, such as tea and pineapple, like the low pH of soils. The amount of lime required depends on the natural acidity of the soil and the specific requirement of the crop. It is impossible to indicate here specific lime requirements for the great variety of crops which can be grown on soils. 
Following article says much about the subject and try to understand the principle behind soil pH and soil chemistry.
Soil pH :What is soil chemistry and what does that mean to me?

Changes in volume composition when the soil get compacted by heavy traffic

A well-managed soil has 25% air, 25% water, 1-5% organic matter and 45-49% mineral solids [Figure 1].




The compacted unamended landscape soil typically has 10% air, 20% water, 1% organic matter and 69% mineral solids. The most significant aspect of the compacted landscape soil is the reduction in air. Low soil oxygen is the most common limiting factor of plant (root) growth. [Figure 2]







Click the link below to get more details

http://www.ext.colostate.edu/mg/Gardennotes/211.html

Can you redraw the pie chart above  when the soil has been under poorly drained, water logging condition.