Calculate how many times greater the mean growth rate per day was using 37.5 g potassium nitrate than using 37.5 g ammonium sulfate.

Assume the mean biomass of the spinach plants at the start of the investigation was 0.5 g per pot.

Using all the information, evaluate the effect on plant growth of adding the different fertilisers to the soil.

The scientist determined the dry mass of the spinach plants. First, he heated each sample at 80 °C for 2 hours.

Suggest what the scientist should do to ensure that he has removed all the water from the sample.