ABSTRACT
This chapter focuses on changing cropping patterns. It begins with an analysis of the gradual improvement in grain seeds over the past several centuries and is followed by a description of changes over time in the extent of wheat and rice double cropping. An important consideration in estimating the impact of improved seeds on the rate of growth in productivity is the pace at which new varieties were discovered and adopted. The principal barriers to increasing the double-cropping acreage result from a combination of weather, inadequate labor and animal power, and inadequate fertilizer. Improved seeds, changing cropping patterns and new crops have all contributed to rising agricultural productivity in China. The principal changes in the cropping pattern that are the possible extension of rice northward, increased double cropping of rice, and greater double cropping of rice or millet with wheat or barley.
