Chemical type Amount used (kg) Fertilizer (NPK) 250 Herbicide 15 Insecticide 8 Fungicide 5 2 Table 2.1 shows the types and amounts of farm chemicals used on...

(a) The total amount of chemicals used is found by adding all four quantities from Table 2.1:

\[ 250 + 15 + 8 + 5 = 278 \text{ kg} \] [1]

(b) The chemical used in the greatest amount is fertilizer (NPK), at 250 kg. [1] This is expected because fertiliser is applied in bulk to supply nutrients to the entire crop, whereas pesticides are used in much smaller targeted doses.

(c)(i) A herbicide is a chemical used to kill weeds (unwanted plants that grow among crops). [1]

(c)(ii) Herbicides are important on a maize farm because:

1. Weeds compete with maize for essential resources such as soil nutrients, water and sunlight. [1]
2. Removing weeds increases the yield of the maize crop by allowing the crop plants to grow without competition and access the full supply of resources. [1]

(d)(i) The term used to describe pests becoming less affected by a pesticide over time is resistance (pest resistance). [1] When the same insecticide is used repeatedly, individuals that happen to survive (because of natural genetic variation) reproduce, and over generations the proportion of resistant individuals in the population increases.

(d)(ii) Two ways the farmer could deal with insecticide resistance:

1. Change to a different insecticide with a different chemical mode of action, so that the resistant individuals are killed by the new compound. [1]
2. Use biological control methods, such as introducing natural predators or parasites of the pest, which do not rely on chemicals and so are unaffected by resistance. [1]

Other acceptable answers: rotate the chemicals used across seasons; adopt integrated pest management (IPM) combining several methods.

(e) Two harmful effects of heavy farm chemical use on the environment:

1. Chemicals can be washed by rainfall into rivers, streams or groundwater, polluting water sources and harming aquatic organisms. [1]
2. Pesticides may kill beneficial insects such as bees (pollinators) and natural predators of pests, reducing biodiversity. [1]

Other acceptable answers: chemicals may accumulate along food chains (bioaccumulation), reaching toxic levels in top predators; prolonged chemical use may reduce soil fertility over time by harming soil organisms.