References on salt use for feeding animals & plants
The Salt Institute's collection of information on salt in animal nutrition is rather comprehensive. The best general texts are Marshall Jurgens, Animal Feeding and Nutrition , W. Pond et al Basic Animal Nutrition and Feeding and Peter McDonald's classic Animal Nutrition ; a good book on applied feeds and feeding is The Mineral Nutrition of Livestock by Underwood and Suttle.
While the major focus of salt and trace mineral nutrition for domestic animals is to ensure against mineral deficiencies, excess mineral consumption remains a clear consideration. The National Academies of Science National Research Council has produced the definitive summary, Mineral Tolerance of Domestic Animals . The chapter on sodium chloride begins on page 441.
Salt is also an important factor in agriculture through its unintended presence in soils where excess concentrations impair fertility. The U.S. Department of Agriculture's Salinity Laboratory at Riverside, CA is an outstanding source for information about soil salinity and efforts to develop salt-tolerant crops.