Sustainable Agriculture Literature Review - Boulder County
Sustainable Agriculture Literature Review - Boulder County
Sustainable Agriculture Literature Review - Boulder County
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6.2 Fertilizers<br />
Fertilizers provide nutrients to improve plant growth and crop yield. Nitrogen is vital to a<br />
plant’s ability to develop proteins and enzymes, which then helps the plant grow. 463<br />
Fertilizer use depends on several factors including soil type, soil fertility, climate, crop<br />
rotations, and price. Although some farmers use organic fertilizers (plant, animal, or<br />
mineral based) and animal manure, synthetic commercial fertilizers are the main type<br />
used in U.S. agriculture. 464, 465 After petroleum fuel and oils, the highest expenditure on<br />
manufactured inputs in Colorado is fertilizers (Figure 24). 466 Commercial fertilizers can<br />
be economical, but like all types of fertilizers, when the plant requirements do not<br />
balance with the amount of fertilization, excess nutrients can contribute to water<br />
contamination. 467 More information on the effects of fertilizers on water contamination<br />
can be viewed in section 4. Water Pollution.<br />
Of the total commercial fertilizer use in the U.S., nitrogen-based fertilizers comprise the<br />
largest portion, with a 56 percent share compared with 24 percent for potash, and 21<br />
percent for phosphate (Graph 11). 468<br />
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Graph 11: U.S. Commercial Fertilizer Use, 1965-2002 469<br />
The cost of commercial fertilizer is greatly increasing. Since nitrogen costs can be the<br />
largest fertilizer expense for farmers, the overall cost of inputs is rising for conventional<br />
farmers. The United States Department of <strong>Agriculture</strong> (USDA) states, “because natural<br />
gas is the main input used to produce ammonia, which, in turn, is the main input used to<br />
produce all nitrogen fertilizers, the volatile and upward-trending price of natural gas in<br />
recent years has affected the price and supply of ammonia, and, thereby, the supply and<br />
price of nitrogen fertilizers, which is a great concern to U.S. agriculture.” 470<br />
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