Fertilizer overuse in Chinese smallholders due to lack of fixed inputs.

Fertilizer overuse by smallholder farmers is widespread in China, leading to significant financial losses and threatening the environment. Understanding what mechanism behind this is critical for agricultural and environmental sustainability. By using a fixed effect panel model of over 20,000 rural households in China from 1995 to 2016, we found that the low ratio of fixed inputs such as machinery and knowledge to total inputs is the key factor leading to over-fertilization in smallholder farms. Low fixed input can result in or interact with nutrient-unbalanced fertilization, low agricultural income ratio and more cash crops that further aggravate fertilizer overuse. Smallholders lack fixed inputs, then compensate by over-applying fertilizer to attempt to achieve their yield goals. Thus, improving fixed input via increasing the average farm size to 3.8 ha or advanced service rental could save not only 45% fertilizers but also increase 16% agricultural net profit, benefiting agricultural and environmental sustainability.

Policy distortions, farm size, and the overuse of agricultural chemicals in China.

Understanding the reasons for overuse of agricultural chemicals is critical to the sustainable development of Chinese agriculture. Using a nationally representative rural household survey from China, we found that farm size is a strong factor that affects the use intensity of agricultural chemicals across farms in China. Statistically, a 1% increase in farm size is associated with a 0.3% and 0.5% decrease in fertilizer and pesticide use per hectare (P < 0.001), respectively, and an almost 1% increase in agricultural labor productivity, while it only leads to a statistically insignificant 0.02% decrease in crop yields. The same pattern was also found using other independently collected data sources from China and an international panel analysis of 74 countries from the 1960s to the 2000s. While economic growth has been associated with increasing farm size in many other countries, in China this relationship has been distorted by land and migration policies, leading to the persistence of small farm size in China. Removing these distortions would decrease agricultural chemical use by 30-50% and the environmental impact of those chemicals by 50% while doubling the total income of all farmers including those who move to urban areas. Removing policy distortions is also likely to complement other remedies to the overuse problem, such as easing farmer's access to modern technologies and knowledge, and improving environmental regulation and enforcement.