In some periods, like the 1800s during the Meiji period, the relationship was an inverse one. Taxation was high and prices were depressed. The result was that farmers were forced away from independent farming and into tenancy. Land rent was paid "in kind" to the landowners; this means that rent was collected in produce of the land rather than in cash. The taxes levied on top of this meant that tenant farmers (1) had to give up most of their crops and send wives and daughters into the labor market and (2) could not expand agricultural development, which in turn stagnated political and social development.
You might find the following links, obtained from searching google books, helpful to you as you research this question:
The first link will take you to information regarding the different agricultural areas of Japan and the impact that this made on their development, and the second is more of an examination of how different agricultural areas led to different economic developments.
This is a great question and it can be answered in many different ways. For one thing, recently less land has been designated for agriculture in Japan. As you can imagine, Japan has limited land and lots of people. For this reason, more land is used for various businesses and industries, which means less land for cultivation. Only 19,000 square miles are used for farmland, which is extremely small for Japan's population of 127,500,000 people. Consider the United States, which cultivated 39,000 square miles in 15 years. And the United states has 51,000,000 square miles of rural space. In light of this, Japan will have to import food, which the government will have to regulate. Also as food prices increase, this will cause strain on the government.