Plants, like animals, need various chemical elements as building blocks for their bodies and for reproduction. Rooted in place, plants have to get most of their necessary minerals from the soil. But harvesting a crop grown year after year in the same soil depletes the store of nutrients, and the soil becomes worn out. Crops now fail to thrive, and the harvest plummets.
Enter the fertilizers, wonderful substances supplying to plants the
nutrients they are unable to extract from the ground or air. Once again, vigorous crops
grace the fields. But as with so many good things, there's a dark side out there.
Rain and irrigation waters leach the fertilizers from the soil, carrying them to
drainage ditches and the river. So? Won't that just make things in the water grow
that much better? Unfortunately, yes. Unfortunate because the nutrients support great
growths of algae and plants, organic matter that, when it dies, enlists oxygen from the
water as part of the decay mechanism. Sensitive aquatic animals are promptly smothered,
and another ecosystem is on its way out!
Contributor: Arthur H. Harris, Laboratory for Environmental Biology, Centennial Museum, University of Texas at El Paso.
Desert Diary is a joint production of the Centennial Museum and KTEP National Public Radio at the University of Texas at El Paso.