A long stream of literature in macroeconomic growth and international development has focused on understanding the large income differences across countries. These income differences are much larger in the agricultural sector than in the non-agricultural sectors of the economy. And since poor countries allocate a large share of their economic resources to the agricultural sector, understanding the sources of low agricultural productivity in these countries is key to understanding underlying reasons for low agricultural incomes. In each chapter of this dissertation, I investigate a possible solution to the issue of large share of economic resources in the low productivity agricultural sector in developing countries. The first chapter studies how agricultural productivity can be increased by a more efficient allocation of resources. The second chapter focuses on improving productivity through increased fertilizer usage in poor countries and the last chapter studies how agricultural incomes can be increased through an open economy and increased trade.