The WTO explicitly prohibits subsidies on export goods to prevent dumping and market distortion but the United States spends $2.4 Billion annually on corn subsidies and has a trade surplus of $19.5 billion in agricultural goods.
How does this subsidy not constitute dumping under the WTO guidelines?
Certain types of agricultural subsidies are permitted under the WTO's Green Box. These include direct income support for farmers, and environmental and regional development programmes. However the rules state that, to qualify, such subsidies must be no more than minimally trade-distorting. Whether such subsidies (in the US and other countries) actually meet that requirement is a matter of controversy, as discussed in this ICTSD Information Note which also shows (in Figure 1) the very high Green Box proportion of US subsidies.
This is a sociology issues than WTO may solved. It is impossible to level the trade playing ground in culture, especially with the ambigous term such as "minimally trade-distorting".
E.g.
Machinery, fertilizer mostly produce in rich nations, thus make it cheaper, even without subsidies.
Corporation from rich country may take a localised diversified animal/crops genes , then charged the research outcome back on the poor country without compensation on the origin.
Agricultural Research grants from government is also a form of subsidies. Should the research lead to a lead on overall production.
crops gene that "borrow" from poor country that do diversified crop planting rarely compensated.
Details of WTO agriculture agreement are available in this link
