FRQ Chp.7/8/9 (2011, #4)

(c) Soil quality is a critical factor in agriculture. Identify TWO physical and/or chemical properties of soils and describe the role of each property in determining soil quality.

(1) PROPERTY: porosity/ pore size ROLE IN DETERMINING SOIL QUALITY: pores allow space for oxygen needed by plant roots/ soil organisms for respiration/ survival (2) PROPERTY: Water-holding capacity ROLE IN DETERMINING SOIL QUALITY: Water is needed by plants for survival/growth.

As the world's population increases and availability of new arable land decreases, providing sufficient food for the world's human population is becoming increasingly difficult. The table below shows the area of land needed to feed the world's population from 1900 projected to the year 2060. *see table* (a) On the graph below, plot the data from the table above and draw a smooth curve.

*see graph on scoring guidelines*

(b) Assume that the maximum arable land area on Earth is 4.00 billion hectares. Using the smooth curve that you created above, determine the year in which the human population is likely to run out of arable land for agriculture.

*see graph on scoring guidelines* 2048

(e) One problem that can result from agriculture is soil salinization. (ii) Describe one method to prevent or remediate soil salinization.

Incorporate organic material into the soil

(e) One problem that can result from agriculture is soil salinization. (i) Describe how salinization occurs.

Salt applied to roads can run off (or splash/spray) and contaminate roadside soil.

(d) Describe TWO viable strategies for reducing the amount of land needed for agriculture

The land needed for agriculture can be reduced by increasing crop yield. This can be done by: (1) Use of (more effective) pesticides/fertilizers could increase crop yield (2) Instituting crop rotation to improve soil fertility could increase crop yield