6-Year Experiment with "Solar Power for Rice Planting" Reduces Rice Yield by 23% but Increases Profit by Five Times
Researchers from the University of Tokyo Conduct Field Experiments and Publish Papers
Experimental Rice Planting with Sunlight
Planting-type Solar Power Plant After Rice Planting
Rice Planted Under Sunlight
Yield in a 6-Year Long-Term Experiment
ns shows no significant difference between rice fields, and *** indicates a significant difference at the 0.1% level. Figures in parentheses are the relative yields of solar-powered rice fields compared to conventional rice fields (Source: Paper by Chun Hau THUM, the University of Tokyo, and others)
On April 1, the University of Tokyo announced the results of a six-year field experiment on the impact of solar power sharing (agricultural solar power generation) on rice production. They estimate that while rice yields could drop by 23 percent, total revenue could increase more than fivefold.
Solar sharing, which combines agriculture with solar power generation, allows crops to be grown and energy produced on the same land, increasing farmers' profits. On the other hand, there are concerns that installing solar panels will reduce crop yields due to reduced solar radiation. In particular, cereals such as rice are said to be more susceptible to the effects of reduced solar radiation than vegetables.
This study investigated the amount of solar radiation, temperature, yield, and quality of rice over six years at a rice production site in Chikusei City, Ibaraki Prefecture, where a solar sharing program is being implemented. The results showed that although rice yields decreased by an average of 23 percent, total revenue from electricity generation was five times higher than that of conventional rice cultivation.
It was also found that changes in microclimate caused by the installation of solar panels reduced yield due to slow growth due to low water temperature, and also reduced panicle number and fertility. Furthermore, it was confirmed that this caused a deterioration in the appearance of brown rice due to an increase in white immature rice grains (immature rice grains with opaque white endosperm) and an increase in protein and amylose content in brown rice, which were associated with a deterioration in flavor.
To date, research on solar energy sharing through rice cultivation has mainly focused on short-term projects of one or two years. This is the first study to investigate the long-term effects of solar energy in agriculture on microclimate, yield and quality of rice. In the future, it is hoped that efforts will be made to develop farming management techniques suitable for solar energy from rice and new rice varieties.
