Siberian agriculture began to send cheap grain westwards beginning around 1869. Agriculture in Central Russia was still under economic pressure after the end of serfdom, which was formally abolished in 1861. To defend the central territory and prevent possible social destabilisation, the Tsarist government introduced the Chelyabinsk tariff-break (Челябинский тарифный перелом) in 1896, a tariff barrier for grain passing through Chelyabinsk, and a similar barrier in Manchuria. This measure changed the nature of export: mills emerged to produce bread from grain in Altai Krai, Novosibirsk and Tomsk, and many farms switched to corn (maize) production.