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.

Isolation of lymphocytes and their innate immune characterizations from liver, intestine, lung and uterus.

In steady-state conditions, the number and distribution of lymphocyte populations are under homeostatic control. New lymphocytes are continuously produced in primary and secondary lymphoid organs and then achieve immune-competence within different tissues, and they must challenge with resident cells for survival. The first step in the study of tissue lymphoid cells is their isolation in intact and viable form appropriate for establishment of in vitro culture systems. For reasons of simplicity, cell purity, cell yields and various purposes, lymphocytes obtained from different tissues in different labs were subjected to diverse protocols. To fully elucidate the nature of the local immune system as well as to adequately study the innate role of lymphocytes in liver, intestine, lung and uterus, we briefly reviewed the characterization of resident lymphocytes, and additional information on those cells from non-lymphoid tissues by using the recommended operation procedure was also presented.