Overuse of agricultural chemicals on China's small farms harms health and environment

The size of farms in China is a key contributor to the overuse of agricultural chemicals, and as a result they may be too small to be environmentally sustainable, a new study has found.

The research -- conducted by a team from the Universities of Melbourne, Zhejiang, Fudan, Wuhan and Stanford -- is published today in the Proceedings of the National Academy of Sciences.

The study found agricultural chemicals are often used inefficiently on small farms, leading to financial losses and serious local, regional and global pollution ranging from eutrophication (an excess of nutrients in bodies of water, often caused by run-off from the land) to particle pollution in the air and global warming.

University of Melbourne and Zhejiang researcher Baojing Gu said: "China is the world's largest consumer of agricultural chemicals, using more than 30 per cent of global fertilisers and pesticides on only 9 per cent of the world's crop land.

"Our study sought to understand the reasons for overuse of agricultural chemicals, because addressing this is critical to the sustainable development of Chinese agriculture," Dr Gu said.

The study used a nationally representative rural household survey from China and found that small farm size strongly affects the use and intensity of agricultural chemicals across farms in China.

A 1 per cent increase in farm size was found to be associated with a 0.3 per cent and 0.5 per cent decrease in fertiliser and pesticide use per hectare respectively. This corresponded to an almost 1 per cent increase in agricultural labour productivity and only an insignificant 0.02 per cent decrease in crop yields.

University of Melbourne Professor Deli Chen said: "In recent years, the Chinese government has made efforts to reduce excessive use of agricultural chemicals, but the effects have unfortunately been limited.

"While economic growth has been associated with increasing farm size in other countries, in China this relationship has been distorted by land and migration policies, leading to the persistence of small farm size," Professor Chen said.

The authors suggest that removing these distortions would decrease agricultural chemical use by 30-50 per cent and the environment impact of those chemicals by 50 per cent, while doubling the total income of all farmers including those who move to urban areas.

"Small farm size has proliferated in China, largely due to the misallocation of cropland and labour caused by the barriers to the movement of labour and the limits on transfer of cropland use rights," Dr Gu said. "This contributes to the overuse of agricultural chemicals in a number of ways.

"Firstly, many technological innovations and modern management practices that reduce the use of agricultural chemicals are less effective on small farms due to the high costs of adoption. People with larger farms typically have better farming knowledge and management skills and so use agricultural chemicals more efficiently than farmers who are operating on a smaller scale."

The study shows average farm size in China has changed very slowly despite the country's strong economic growth and urbanisation. From the 1980s to 2000s, the country's average farm size decreased and has increased slowly since the 2000s. This pattern differs substantially from other developed countries.

It also shows 98 per cent of households that run farms own a farm measuring less than 2 hectares in China -- a much higher proportion than in other world regions, even Africa.

"The findings in our paper have far-reaching implications for many less-developed countries. While agriculture in less-developed countries, especially in some sub-Saharan African countries, is currently suffering from a deficit in agricultural chemicals, their availability will increase with economic growth," Professor Chen said.

"If nothing is done to address the misallocation of land, labour and capital in agriculture in these countries, they will face the same problems and implications for health and the environment that Chinese agriculture has experienced for the past few decades."