The increase of Soviet agricultural production was tremendous, however, the Soviet-Ukrainians still experienced food shortages due to the inefficiencies of a highly centralised economy. During the peak of Soviet-Ukrainian agriculture output in the 1950s and early-to-mid-1960s, human consumption in Ukraine, and in the rest of the Soviet Union, actually experienced short intervals of decrease. There are many reasons for this inefficiency, but its origins can be traced back to the single-purchaser and -producer market system set up by Joseph Stalin. Khrushchev tried to improve the agricultural situation in the Soviet Union by expanding the total crop size – for instance, in the Ukrainian SSR alone "the amount of land planted with corn grew by 600 percent". At the height of this policy, between 1959 and 1963, one-third of Ukrainian arable land grew this crop. This policy decreased the total production of wheat and rye; Khrushchev had anticipated this, and the production of wheat and rye moved to Soviet Central Asia as part of the Virgin Lands Campaign. Khrushchev's agricultural policy failed, and in 1963 the Soviet Union had to import food from abroad. The total level of agricultural productivity in Ukraine decreased sharply during this period, but recovered in the 1970s and 1980s during Leonid Brezhnev's rule.