IB ESS HL 5.1.7 Soil Transformations Questions

inverse / negative;
b. as (irrigation water) salinity increases, crop yield potential decreases / as salinity decreases, crop potential increases;

Note: Do not accept in the converse. e.g. 'as crop yield potential decreases it causes the salinity to increase’.

a. irrigation water is often pumped up from underground/from wells;
b. groundwater contains (mineral) salts / water used for irrigation may contain salts/be saline;
c. in areas of high evaporation/dry/semi-arid climates, water evaporates from the surface, leaving salts behind;
d. the dissolved sodium ( $\mathrm{Na}^{+}$) and chloride ( $\mathrm{Cl}^{-}$) ions can displace other mineral nutrients in the soil needed for plant growth, such as potassium (K) and phosphorus (P) / minerals required for plant growth are replaced ;
e. salin(is)ation of soils/over time the salts build up, leading to levels higher than macroinvertebrates/decomposers can tolerate;
f. reduction in macroinvertebrates/decomposers may reduce nutrient cycling;
g. excessive irrigation can lead to leaching of nutrients from the soil (reducing soil fertility) / irrigation can lead to erosion of fertile top soil;
h. excessive irrigation can lead to water-logging/rise in water table and poor aeration of the soil, reducing nutrient cycling;
i. irrigation leads to an increase in plant growth that utilizes/absorbs nutrients from the soil (hence reducing soil fertility over time);

Note: do not accept just "salin(is)ation" or "leaching" as this does not explain why loss of soil fertility occurs.