Any chemical used in agriculture , including chemical fertilizers , herbicides , and insecticides .
Most are mixtures of two or more chemicals; active ingredients provide the desired effects, and inert ingredients stabilize or preserve the active ingredients or aid in application. Together with other technological advances, including tractors, mechanical harvesters, and irrigation pumps, agrochemicals have increased the per-acre productivity of regions such as the Great Plains by 200–300% since the 1930s. Their long-term effects on the environment and the stability of agricultural systems that use them are hotly debated.