(b) the grassland is ploughed up and turned into farmland. crops of maize are grown on it
year after year.
(i)
predict and explain the effect of this change on the nitrogen cycle and on the crop
yield.

--effect on the nitrogen cycle
--effect on crop yield

(ii) suggest one way in which the farmer could prevent the effect on crop yield.

1.

i. Effect on the nitrogen cycle

will go on smoothly

ii. Effect on crop yield  

will reduce

2.

Farmer must do crop rotation in alternate season

Explanation:

1.

Effect on the nitrogen cycle

Crop rotation is essential to restore the nitrogen content of the soil. Generally in one season a non leguminous crop is grown while in the other season a leguminous crop is grown. Leguminous crop allows the nitrogen with in the soil to be restored by the rizhobium bacterium. Since here only maize is grown year after year,  the nitrogen cycle will go on smoothly.

Effect on crop yield

Crop yield will decrease as if same kind of crop is grown again and again,  it causes depletion of essential soil and mineral from the soil and since crop change is not done thus no time is even allowed for restoration of such crops. Hence, crop yield will decrease ultimately.

2.

Crop rotation must be done and some leguminous crops can be grown in alternate seasons to enhance the crop yield.

the answer would be d

currents is the correct answer.