Topic 20.1 · Core
Increasing Food Production
Five methods sit under this heading, and an exam answer that just names one of them is only halfway there. Cambridge wants the mechanism: what the method removes, replaces or selects for, and why that specific change leads to more food.
Agricultural machinery
Machinery lets a farmer prepare, sow, manage and harvest a much larger area of land than human labour alone could cover, and it does each of those jobs faster. Speed matters for a reason that’s easy to miss: a crop harvested promptly, at the right point in its development, loses less to spoilage or pests than one left standing because there wasn’t time to bring it in. The relationship worth holding onto for an exam answer is greater farming efficiency and a larger workable area leading to increased food production— not just “machines help farmers.”
Chemical fertilisers
Plants need mineral ions to grow, and every harvest removes some of those ions from the soil along with the crop. Chemical fertilisersreplace the ions that growth actually depends on — nitrate ions, for instance, are needed to build amino acids and proteins — so a soil that would otherwise become depleted keeps supporting strong growth season after season. It’s worth being precise about the limits here too: once some other factor becomes limiting, adding still more fertiliser stops raising yield, and any fertiliser the crop doesn’t take up doesn’t just disappear. It can be washed into rivers and lakes, which is where this method’s benefit for a field becomes a cost for a completely different ecosystem — covered in full on water pollution.
Insecticides
Insect pests eat crop plants and damage leaves, stems, roots, fruit or seeds, which lowers both the quality and the total yield of what’s harvested. Insecticides kill or control those insect pests, so less of the crop is lost to feeding damage before it ever reaches harvest.
Herbicides
Weeds are simply plants growing where a farmer doesn’t want them, and they compete directly with the crop for light, water, mineral ions and space. Herbicides kill or control those unwanted plants, which frees up the resources a crop needs to grow well.
Insecticides and herbicides are easy to swap by accident under exam pressure, so it’s worth fixing the distinction in one sentence: an insecticide controls insect pests, and a herbicide controls weeds. They solve two different competition problems, not the same one twice.
Selective breeding
Selective breedingmeans choosing parents that show a desirable inherited characteristic and breeding from them, so that characteristic becomes more common in the next generation. Applied to agriculture, this can produce crop varieties with higher yields or more desirable fruit and seeds, and livestock that produce more meat, milk or eggs. The full mechanism of how selective breeding actually changes a population’s characteristics over generations belongs to the variation and selection topic in Chapter 18 — what matters here is narrower: selective breeding is one more route by which humans raise agricultural output, alongside machinery, fertilisers, insecticides and herbicides.
Where this leads
These five methods rarely operate one at a time. In practice they’re combined and applied intensively across large areas — which is exactly what a large-scale monoculture or an intensive livestock systemdoes, with its own separate set of advantages and disadvantages that go beyond simply “more food.”