Agriculture in future will be different to today's agribusiness with its enormous dependence on fossil fuel created artificial fertiliser and pesticides etc. Peak oil will force a change whether existing systems like it or not.
Most of this high energy/high carbon footprint fossil fuel dependency is because the dominant model of farming is currently monoculture where one crop species is grown in large fields. Pests, when they find such a field, tend to run riot thus farmers "need" to attack them with the heavy artillery of pesticides and fungicides to control them to avoid losing the whole crop. This simple cartoon shows how "polyculture" avoids many of those problems. As usual, if you find the image too small to read, click on it to see the original larger picture.