Artificial fertiliser is used to replace mineral ions removed from the land when crops are harvested. One of the mineral ions is nitrate.

Give two examples of biological molecules containing nitrogen that would be removed when a crop is harvested.

1

2

Scientists investigated changes in the use of artificial fertiliser in India between 1970 and 2005. They also investigated changes in the fertiliser response ratio.

This ratio shows how many kg of grain are produced for each kg of fertiliser used.

Figure 4 shows their results in the form the scientists presented them.

(A hectare is a unit of area commonly used in agriculture)

Use these data to calculate the difference in the mass of grain produced per hectare in 1970 compared with 2005.

Show your working.

Difference ______________ kg hectare−1

Use the data in Figure 4 to evaluate the use of artificial fertilisers on grain-producing crops in India.