Fertilizers

Introduction

Fertilizers are chemicals containing plant nutrients that are added to plant environments.   Usually, they are added to the water or soil, but some fertilizers are sprayed on leaves.   Plants use nutrients available from the air, water, and soil plus the nutrient supplements provided by fertilizers to produce food with sufficient light and proper temperautes.

Crops (plants used for animal consumption) require nutrients to grow, but deplete some of them from the soil.   Animal manure (bird manure is called "guano") used to replenish the soil of minerals is an ancient way of fertilizing the soil; that is, returning minerals used by the plants that were, in turn, eaten by the animals.   However, animal manure contains disease-bearing organisms and smells.   Nutrients provided by manufactured chemicals are easier, cheaper and healthier substitutes to natural fertilizers.

To 1790

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In 1842, the English scientist, John Lawes, patented the method for making what he called superphosphate, the first chemical fertilizer that improved soil productivity, reduced disease sources, and made the barnyard smell much better. ^{Asimov 345}

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In 1892, the boll weevil, a central American beetle, was seen in Texas and spread across the cotton-growing regions to severly damage cotton crops. ^{Carruth 361}

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