The Need for Nitrogen Use Efficiency to Reduce Environmental Impacts on the Gulf of Mexico BY Dually Bertholf BAE 4213 Spring 2003

Fun Facts Length of the Mississippi River: 3,705 kilometers (2,302 miles) Length of the Mississippi River: 3,705 kilometers (2,302 miles) Area of Basin: Area of Basin: 3.2 million square kilometers (1.2 million square miles). 3.2 million square kilometers (1.2 million square miles). 40% of the United States 40% of the United States 1/8 of North America 1/8 of North America Population along the Mississippi Corridor: 12 million people live in the 125 counties and parishes that border the Mississippi River. Population along the Mississippi Corridor: 12 million people live in the 125 counties and parishes that border the Mississippi River. Amount of water discharged to the Gulf: 612,000 cubic feet per second Amount of water discharged to the Gulf: 612,000 cubic feet per second Provides habitat for Provides habitat for 241 fish species 241 fish species 37 mussel species 37 mussel species 45 amphibians 45 amphibians 50 mammals 50 mammals 40% of the nation's migratory birds 40% of the nation's migratory birds

Mississippi River Basin The Mississippi basin, the largest river basin in the United States, forms a wedge of 1,243,000 square miles (3,220,000 sq. km.) in the center of the continent, and is made up of three major branches, the Mississippi which the middle branch drains 171,500 square miles (444,300 sq. km.), the Missouri drains approximately 530,000 square miles (1,373,000 sq. km.), and the Ohio which drains 202,000 square miles (523,000 sq. km.). Below the Ohio, the lower Mississippi gathers water from several other smaller basins, namely the Arkansas and the Red River. The Mississippi basin, the largest river basin in the United States, forms a wedge of 1,243,000 square miles (3,220,000 sq. km.) in the center of the continent, and is made up of three major branches, the Mississippi which the middle branch drains 171,500 square miles (444,300 sq. km.), the Missouri drains approximately 530,000 square miles (1,373,000 sq. km.), and the Ohio which drains 202,000 square miles (523,000 sq. km.). Below the Ohio, the lower Mississippi gathers water from several other smaller basins, namely the Arkansas and the Red River.

Mississippi River Basin Cont. In 1990, Mississippi Basin farmers applied 21 billion pounds of fertilizer. In 1990, Mississippi Basin farmers applied 21 billion pounds of fertilizer. A 12 percent reduction in nitrogen fertilizer use could have a 33 percent reduction in the nitrate flux in the Mississippi River and Gulf of Mexico. A 12 percent reduction in nitrogen fertilizer use could have a 33 percent reduction in the nitrate flux in the Mississippi River and Gulf of Mexico. Total nitrogen flux into the Mississippi river basin has been estimated to have tripled over the last 35 years. Total nitrogen flux into the Mississippi river basin has been estimated to have tripled over the last 35 years.

Mississippi River Information It drains 41 percent of the contiguous U.S. It drains 41 percent of the contiguous U.S. Covers 55 percent of U.S. agricultural lands. Covers 55 percent of U.S. agricultural lands. Includes 33 major river systems and 207 estuaries. Includes 33 major river systems and 207 estuaries. Includes 27 percent of U.S. population. Includes 27 percent of U.S. population. Includes about 80 percent of U.S. corn and soybean Includes about 80 percent of U.S. corn and soybean acreages, and much of the cotton, rice, sorghum, acreages, and much of the cotton, rice, sorghum, wheat, and forage lands. wheat, and forage lands.

Mississippi River Information Cont. Is the source of 72 percent of U.S. harvested shrimp, Is the source of 72 percent of U.S. harvested shrimp, 66 percent of the harvested oysters, and 16 percent of 66 percent of the harvested oysters, and 16 percent of the U.S. commercial fish harvest the U.S. commercial fish harvest Has fisheries valued annually at over $700 million at Has fisheries valued annually at over $700 million at dockside. Its commercial and recreational fisheries dockside. Its commercial and recreational fisheries have a combined value of $2.4 billion per year. have a combined value of $2.4 billion per year.

Definitions Hypoxia: Hypoxia refers to dissolved oxygen concentrations less than 2 mg/L (milligrams per liter). Hypoxia can cause stress or death in bottom-dwelling organisms that can not leave the zone. Hypoxia is caused primarily by excess nitrogen delivered from the Mississippi River in combination with seasonal stratification of Gulf waters. Nitrogen promotes algal and attendant zooplankton growth. The associated organic matter sinks to the bottom where it decomposes, consuming available oxygen. Stratification of fresh and saline waters prevents oxygen replenishment by mixing of oxygen-rich surface water with oxygen-depleted bottom water. Hypoxia: Hypoxia refers to dissolved oxygen concentrations less than 2 mg/L (milligrams per liter). Hypoxia can cause stress or death in bottom-dwelling organisms that can not leave the zone. Hypoxia is caused primarily by excess nitrogen delivered from the Mississippi River in combination with seasonal stratification of Gulf waters. Nitrogen promotes algal and attendant zooplankton growth. The associated organic matter sinks to the bottom where it decomposes, consuming available oxygen. Stratification of fresh and saline waters prevents oxygen replenishment by mixing of oxygen-rich surface water with oxygen-depleted bottom water.

Definitions Cont. Eutrophication—The process of being enriched in Eutrophication—The process of being enriched in dissolved nutrients, especially nitrate (NO3) and dissolved nutrients, especially nitrate (NO3) and phosphate. Eutrophication can enhance phytoplankton phosphate. Eutrophication can enhance phytoplankton (microscopic, passively floating plants) growth. (microscopic, passively floating plants) growth. This increased growth can cause an increase in This increased growth can cause an increase in organic matter deposition. As the organic matter organic matter deposition. As the organic matter from dead phytoplankton and fecal residues from from dead phytoplankton and fecal residues from zooplankton (which feed on the phytoplankton) zooplankton (which feed on the phytoplankton) drops to the bottom waters, microorganisms decompose drops to the bottom waters, microorganisms decompose it and deplete dissolved O2 from the water. it and deplete dissolved O2 from the water. drops to the bottom waters, microorganisms decompose drops to the bottom waters, microorganisms decompose it and deplete dissolved O2 from the water. it and deplete dissolved O2 from the water.

N Source N Source Short Tons Mineralized soil N 7,497,404 Fertilizer N 7,497,094 Legume N fixation 4,445,155 All manure N 3,582,911 Atmospheric wet and dry deposition of nitrate-N 1,461,656 Atmospheric deposition of ammonium-N 663,497 Municipal point sources of N 221,266 Industrial point sources of N 94,370 Hypoxia.pdf

Nflux = 0.049*F2 + 36*Q *R1 Nflux: Nitrate flux to the Gulf, in metric tons per year. Nflux: Nitrate flux to the Gulf, in metric tons per year. F2: Fertilizer use in the entire basin 2 years previous, in metric tons. F2: Fertilizer use in the entire basin 2 years previous, in metric tons. Q: Current year mean annual discharge to the Gulf, in cubic meters per second. Q: Current year mean annual discharge to the Gulf, in cubic meters per second. R1: Nitrogen residual for the previous year, in metric tons. R1: Nitrogen residual for the previous year, in metric tons.

Nflux = 0.049*F2 + 36*Q *R1 R² of

Hypoxia in the Gulf of Mexico Hypoxic waters are distributed from shallow depths near shore (4 to 5 m) to as deep as 60 m, but are present more typically between 5 and 30 m. Hypoxia occurs mostly in the lower water column but encompasses as much as the lower half to two-thirds of the column. pg.17 par.5 Hypoxic waters are distributed from shallow depths near shore (4 to 5 m) to as deep as 60 m, but are present more typically between 5 and 30 m. Hypoxia occurs mostly in the lower water column but encompasses as much as the lower half to two-thirds of the column. pg.17 par.5 Hypoxia covers broad regions of the shelf for extended periods in mid-summer. In 1985–92, the midsummer bottom areal extent of hypoxic waters (< 2 mg/l O2, or ppm) averaged 8,000–9,000 km2; in 1993– 97 it increased to 16,000–18,000 km2. The estimated extent was 12,500 km2 in mid-summer of pg.17 par.3 Hypoxia covers broad regions of the shelf for extended periods in mid-summer. In 1985–92, the midsummer bottom areal extent of hypoxic waters (< 2 mg/l O2, or ppm) averaged 8,000–9,000 km2; in 1993– 97 it increased to 16,000–18,000 km2. The estimated extent was 12,500 km2 in mid-summer of pg.17 par.3

Hypoxia in the Gulf of Mexico Cont. Hypoxia occurs not only at the bottom near the sediments, but well up into the water column (see Sections 3.2 and 3.4). Depending on the depth of the water and the location of the pycnocline(s), hypoxia may encompass from 10% to over 80% of the total water column, but normally encompasses 20–50%. Hypoxia may reach to within 2 m of the surface in a 10-m water column, or to within 6 m of the surface in a 20-m water column. Anoxic bottom waters can occur, along with the release of toxic hydrogen sulfide from the sediments. pg.24 par.2 Hypoxia occurs not only at the bottom near the sediments, but well up into the water column (see Sections 3.2 and 3.4). Depending on the depth of the water and the location of the pycnocline(s), hypoxia may encompass from 10% to over 80% of the total water column, but normally encompasses 20–50%. Hypoxia may reach to within 2 m of the surface in a 10-m water column, or to within 6 m of the surface in a 20-m water column. Anoxic bottom waters can occur, along with the release of toxic hydrogen sulfide from the sediments. pg.24 par.2

Factors That Influence Hypoxia Levels in the Gulf of Mexico Changes in precipitation patterns and quantities Changes in precipitation patterns and quantities within the Mississippi River Basin within the Mississippi River Basin Increased Mississippi River flow and fresh water Increased Mississippi River flow and fresh water stratification over salt water stratification over salt water Complex interactions among marine organisms Complex interactions among marine organisms Increased or sustained large fisheries harvests Increased or sustained large fisheries harvests Gulf storms and hurricanes Gulf storms and hurricanes Tidal currents and their characteristics (temperature, Tidal currents and their characteristics (temperature, circulation, etc.) circulation, etc.) Loss of coastal wetlands (25-35 square miles/year in Loss of coastal wetlands (25-35 square miles/year in Louisiana alone) Louisiana alone) Nutrients from re-suspended N sediments and Nutrients from re-suspended N sediments and upwelling off the Yucatan Peninsula upwelling off the Yucatan Peninsula

Thoughts Increase Nitrogen Use Efficiency by stressing the importance to the plant breeders, so they will develop more efficient breeds of plants. Increase Nitrogen Use Efficiency by stressing the importance to the plant breeders, so they will develop more efficient breeds of plants. Use site specific farming practices to only apply fertilizers, insecticides, and herbicides. Use site specific farming practices to only apply fertilizers, insecticides, and herbicides. Only apply what is needed for the specific areas and at the appropriate time. Only apply what is needed for the specific areas and at the appropriate time. With the help of new technologies and the willingness of the people we will have a safe and productive future. With the help of new technologies and the willingness of the people we will have a safe and productive future.

Questions?

References far.org/ppiweb/usams.nsf/$webindex/A265C63DD1C7B81E C22C0?o pendocument&navigator=home+page far.org/ppiweb/usams.nsf/$webindex/A265C63DD1C7B81E C22C0?o pendocument&navigator=home+page far.org/ppiweb/usams.nsf/$webindex/A265C63DD1C7B81E C22C0?o pendocument&navigator=home+page far.org/ppiweb/usams.nsf/$webindex/A265C63DD1C7B81E C22C0?o pendocument&navigator=home+page

References Cont THE-GULF-OF-MEXICO.htm THE-GULF-OF-MEXICO.htm THE-GULF-OF-MEXICO.htm THE-GULF-OF-MEXICO.htm

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References Cont far.org/ppiweb/usams.nsf/$webindex/014300E14A C40007D7 A82?opendocument&navigator=home+page far.org/ppiweb/usams.nsf/$webindex/014300E14A C40007D7 A82?opendocument&navigator=home+page far.org/ppiweb/usams.nsf/$webindex/014300E14A C40007D7 A82?opendocument&navigator=home+page far.org/ppiweb/usams.nsf/$webindex/014300E14A C40007D7 A82?opendocument&navigator=home+page

References Cont ppic.org/ppiweb/ppinews.nsf/$webcontents/A1A0DBBD5BBAF E 5E90/$file/99176-Hypoxia.pdf ppic.org/ppiweb/ppinews.nsf/$webcontents/A1A0DBBD5BBAF E 5E90/$file/99176-Hypoxia.pdf ppic.org/ppiweb/ppinews.nsf/$webcontents/A1A0DBBD5BBAF E 5E90/$file/99176-Hypoxia.pdf ppic.org/ppiweb/ppinews.nsf/$webcontents/A1A0DBBD5BBAF E 5E90/$file/99176-Hypoxia.pdf