(a(i))[2]
Calculate the difference between the average yields of the two plots within the field as a percentage of the average yield of the control plots.
(a(ii))[3]
Explain why the average yield increased after the fertiliser was added.
(a(iii))[1]
State the name of the process that happens when fertiliser is washed from land into rivers and results in an algal bloom.
(b)[3]
Describe the effect of fertiliser on the plant species diversity shown in Fig. 5.1.
(c)[2]
Suggest why certain plant species survive in grassland whereas others do not.