A lot of variables go into agricultural success, some guided by the hand of nature, others by the intellect of man. In the latter category is a five-year, $2.5 million research project with the unwieldy moniker of “Qualitative Assessments of Water and Salt Balance for Cropping Systems in Lower Colorado River Irrigation Districts.” It takes place in Yuma, Ariz., smothered in sunshine, the winter leafy greens capital of the world.  That’s in the clear, cool, dry climate of winter.