Agriculture Reference
In-Depth Information
74 Earthworms became extinct in North America during the
past couple of Ice Ages and were re-introduced by European
explorers.
75 Exner, Rick, “Soil Fertility Management Strategies -
Philosophies, Crop Response, and Costs” (Iowa State
University, University Extension, 2007)
76 Yellowing of old leaves is a sign of nitrogen deficiency.
77 This practice prevents the appearance of a disease called
“club-foot”.
Search WWH ::




Custom Search