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SL 241 Characterizing Agriculture in Floridas Lower Suwannee River Basin Area 1 Tom Obreza and Greg Means2 Introduction The Suwannee River is a major aquatic resour ce that begins in Georgia and flows through north Florida until it empties into the eastern Gulf of Mexico. About two-thirds of the river basin is in Georgia, while the other one-third, known as the Lower Suwannee Basin, is in Florida (Figure 1). The Lower Suwannee Basin forms the central portion of the Suwannee River Water Management District (SRWMD) (http://www.srwmd.s tate.fl.us), which encompasses all or parts of 15 counties (Figure 2). Figure 1. Florida's Lower Suwannee River Basin (in green) and surrounding area. The Lower Suwannee Basin is designated as a Showcase Watershed by the U.S. Environmental Protection Agency. It contai ns the highest concentration of firstmagnitude freshwater springs in the world. (A first magnitude spring is one that 1. This document is SL 241, a fact sheet of the Soil and Wate r Science Department, Florida C ooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Original publication date: May 2006. Visit the EDIS Web Site at http://edis.ifas.ufl.edu 2. Tom Obreza, professor, and Greg Means, biological scientist, Soil and Water Science Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, FL 32611-0290. The Institute of Food and Agricultural Sciences is an equal o pportunity/affirmative action emplo yer authorized to provide resea rch, educational information and other services only to individuals and institutions that function without regard to race, color, se x, age, handicap, or national origin. For information on obtaining othe r extension publications, contact your county Cooperative Extens ion Service office. Florida Cooperative Extension Service, Institute of Food and Agricu ltural Sciences, University of Florida. Larr y R. Arrington, Dean.
2 discharges at least 100 cubic feet of water per second, or about 64.6 million gallons per day.) During the last 20 years, the nitrat e-N concentration of some of the basins rivers and springs has increased to the point of envir onmental concern. In response, the states of Florida and Georgia, the Federal government, and other local organiza tions have identified the Suwannee River Basin as an ecosystem in need of protection because of its unique biota and important water resources. Figure 2. Boundary of the Suwannee River Water Management District. Objective of this Publication The Suwannee River Partnership (http://www.suwannee.org) was formed in 1999 to determine the sources of nutrient loads in the ri ver basin, and to work with local land users to minimize future nutrient loading through voluntar y, incentive-based programs. Agriculture and forestry are the dominant land uses in the waters hed. While the environmental impact of forestry is usually low, intensive agri cultural production has th e potential to aff ect water quality if nutrients and water are not carefully managed. Agriculture in the Lower Suwannee Basin is diverse--beef, dairy, poultry, field crop, forage, vegetable, and nursery production are all found there. Nutrient and water management issues important to environmental protection vary between these agricultural segments, so it is imperative to understand how they are spatially distributed throughout the 7,640 square mile area of the SRWMD. Therefore, the objective of this publication is to characterize agriculture in Floridas Lower Suwannee Basin Area so that Be st Management Practice educational programs can be appropriately developed and effici ently delivered to key target audiences.
3 Data Sources and Collection Method Data sources Agricultural production data: Florida Agri cultural Statistics Service (FASS) (http://www.nass.usda.gov/Statistics_by_State/Florida/index.asp) Pine plantations: Florida Geographic Data Library (http://www.fgdl.org) Soil characteristics: USDA-NRCS county soil surveys Population: U.S. Census Bureau (http://quickfacts.census.gov/qfd/states/12000.html) Fertilizer consumption: Florida Dept. of Agriculture and Consumer Services (FDACS), Fertilizer Section (http://www.doacs.s tate.fl.us/onestop/aes/fertilizer.html) Irrigation: U.S. Geological Survey Data collection Data were obtained on a county-by-county ba sis. The SRWMD includes all of Columbia, Dixie, Gilchrist, Hamilton, Lafayette, Madison, Su wannee, Taylor, and Union counties, and parts of Alachua, Baker, Bradford, Jefferson, Levy, and Putnam counties. Since the District includes only portions of six counties, this report covers an area slightly larger than the entire Lower Suwannee River basin. The portions of Baker and Putnam counties within the District boundary are small and were deemed insignificant for the pu rpose of this report, so they were not included in the summaries. However, the reader is cautioned t hat the reported data for Alachua, Bradford, Jefferson, and Levy counties represent the en tire county, not all of which falls within the SRWMD or the Lower Suwannee River Basin watershed In some cases, agricultural production data were not available from FASS for particular counties where the number of farms for a given operation type were small, possibly compromising anonymity of the farms. In these cases, data could not be included in the overall summary, so severa l of the analyses are incomplete Characterizing the Basin Population The population of the 13 counties representing Floridas Lower Suwannee Basin area was 507,155 in 2004, but 44% of the total (223,090) was in Alachua county. The remaining counties had considerably lower population density (Fi gure 3) and remained rural in nature, although counties immediately north and west of Alachua were roughly twice as densely-populated as the rest due to influence of population centers like Live Oak, Lake City, Gainesville, and Jacksonville.
4 Figure 3. Population density (persons per square mile) in 2004. Landscape and soil characteristics The basin is generally flat with occasiona l rolling topography. Elevation ranges from sea level at the Gulf coast to around 180 ft in parts of Jefferson, Madison, Hamilton, Suwannee, Columbia, and Alachua counties (Figure 4). Soil er osion can be a localized problem in some sloping agricultural fields, but in general it is not a major issue across the basin. Most rain and irrigation water infiltrates the soil unless soil crusting has occurred, which can increase runoff to ditches and streams. Figure 4. Land elevation in Florida's Lower Suwannee Basin area.
5 Most of the soils used for agricultural production are classified as Entisols, Ultisols, or Spodosols. These soil orders cannot be differentiated from one another by observing only the surface soil (plow layer) because they are similar. One must look deeper in the profile to find differences. Entisols (Figure 5, top) have little or no evidence of so il formation, and the entire profile is sandy throughout. The reason for th is is that not enough time has elapsed for soil-forming processes to act following depos ition of the sandy material by the ocean. Ultisols (Figure 5, middle) have a sub-surf ace layer of loamy material (Bt horizon) due to the downward movement and accumulati on of clay. This clay is acidic and low in plant nutrient content. Spodosols (Figure 5, bottom) have a black, brown, or reddish-brown subsoil layer called a spodic (Bh) horizon. This layer is often overlain by a light-gray to whitish layer (E horizon). The spodic horizon is an accumulation of organic matter, aluminum, and iron compounds that leached from a surface litter layer. Sometimes a Bt horizon is found below the Bh horizon, but a Bh never occurs below a Bt.
6 Figure 5. Distribution of three major soil orders used for agricultural production in north Florida, and examples of their profiles.
7 Regardless of soil order, the root zone (A horiz on) texture in the basi n is usually sand or fine sand. Some Ultisols can have a slightly more loamy texture (e.g. loamy sand) at the surface. Compared with agricultural soils in other parts of the USA, the water-holding capacity of north Florida soils is low (Table 1). Water-holding capacity of a typical Midwestern corn belt soil is two to three times higher th an a sandy Florida soil. Table 1. Soil texture eff ect on water-holding capacity. Water-holding capacity, inches/foot Texture Low High Average Sand, Fine sand 0.24 1.20 0.75 Loamy sand, Loamy fine sand 0.36 1.44 1.00 Sandy loam, Fine sandy loam 0.90 1.80 1.40 Soil nutrient-holding capacity as measured by soil cation exchange capacity (CEC) and organic matter content is also low (Table 2). Although Ultisols and Spodosols have higher CEC in the Bt and Bh horizons, these layers do not support root growth due to high acidity, compaction, or low oxygen content. The organi c matter accumulated in a Bh horizon does not contribute to soil fertility because of high acidity and aluminum toxicity associated with it. Table 2. Nutrient-holding capacity factors for three north Florida soil orders. Soil order Property Depth Entisol Ultisol Spodosol Plow layer (A horizon) 3 5 4 Cation exchange capacity (meq/100 g) Sub-surface 1 (C horizon) 15 (Bt horizon) 19 (Bh horizon) Plow layer (A horizon) 0.8 1.0 1.2 Organic matter (%) Sub-surface 0.2 (C horizon) 0.1 (Bt horizon) 4.5 (Bh horizon) Of the three soil orders, Entisols are most vulnerable to leaching of nutrients and agrichemicals because they are sandy throughout, contain little organic matter, are highly conductive to water flow, and have no sub-surface layer that can slow wa ter drainage through the profile. Six of the thirteen counties in the Lo wer Suwannee Basin area have more than 20% of their area mapped as Entisols (Figure 5). The highest concentration runs along a straight line through Hamilton, Suwannee, and Gilchrist coun ties, increasing from north to south. Extent of farmland and planted pineland Most counties in the Lower Suwannee Basin ar ea had between one-quarter and one-third of their land area devoted to pine plantations (Figure 6). Taylor county contained the largest acreage of commercial pine forest by a wide margin, followed by Columbia and Levy counties (Table 3). Counties with the largest per centage of total land area devo ted to farms were Alachua, Suwannee, Union, Gilchrist, Jefferson, and Madi son (Figure 6). Alachua had the most farm
8 acres, followed by Levy, Suwannee, Madison, and Jefferson (Table 3). Taylor had the largest average farm size, followed by Lafayette, Jefferson, and Madison. Figure 6. Relative amount of land occupied by farms and pine plantations. Table 3. Land area devoted to farming and pine plantations by county. County Pine plantation acreage (1995) Farm acreage (2002) Number of farms Average farm size (ac) Alachua 156,759 222,728 1,493 149 Bradford 60,725 44,819 378 119 Columbia 179,210 90,227 688 131 Dixie 155,593 31,249 215 145 Gilchrist 54,435 81,489 408 200 Hamilton 103,873 52,027 239 218 Jefferson 119,297 132,727 418 318 Lafayette 94,695 91,988 195 472 Levy 179,993 180,314 897 201 Madison 111,455 156,995 529 297 Suwannee 105,400 170,149 1,054 161 Taylor 237,435 53,720 101 532 Union 56,944 59,635 275 217 Market value of farm production Suwannee County had the highest market value of farm production by a wide margin compared with other counties (Figure 7). Following Suwannee were Levy, Alachua, Lafayette, Columbia, and Gilchrist.
9 Figure 7. Market value of total farm production in millions of dollars (2002). Field crops Floridas Lower Suwannee Basin is a ma jor field crop producti on area. Field crop distribution was determined for all crops combin ed, and for three crop sub-categories (Table 4). Table 4. Sub-division of field crops and specific crops within each category. Grains, Grain Silage and other Field Crops Hay, Forage, & Seeds Vegetables & Melons Corn Field & grass seeds Beans (snap) Oats Alfalfa hay Broccoli Rye Small grain hay Cabbage (Chinese and head) Sorghum Other tame hay Cantaloupes Wheat Wild hay Collards Cowpeas Haylage, all Cucumbers Peanuts Eggplant Potatoes Lettuce Soybeans Mustard greens Tobacco Okra Peas Peppers Radishes Squash Sweet corn Tomatoes Watermelons
10 Field crop production was grea test in Alachua, Levy, and Suwannee counties (Fig. 8). Levy had the most acreage devoted to major (non -vegetable) row crops, Al achua had the greatest hay and forage acreage, and Suwannee had the mo st acreage of vegetables and melons. In 2002, of Floridas 67 counties: Alachua ranked no. 1 in land area devoted to forage and hay production, and no. 2 in silage corn. Gilchrist ranked no. 4 in silage corn and no. 1 in silage sorghum. Hamilton ranked no. 4 in grain corn and no. 3 in cowpeas. Jefferson ranked no. 2 in grain corn and no. 4 in cowpeas. Levy ranked no. 2 in peanuts and no. 1 in silage corn. Madison ranked no.1 in grain corn, grain rye, cowpeas, and soybeans. Suwannee ranked no. 4 in forage and hay, no. 5 in peanuts, no. 3 in silage corn, no. 3 in sweet corn, and no. 7 in all vegetables harvested. Figure 8. Cropland acreage in Florida's Lower Suwannee River Basin area (2002). *Some crop data in these counties was excluded from the ag census to avoid disclosing individual farms.
11Animal agriculture Floridas Lower Suwannee Basin area contains significant animal agriculture (Fig. 9). For example, in 2002, of Floridas 67 counties: Suwannee ranked no. 1 in sales value of poultry and eggs. Columbia ranked no. 1 in laying hen inve ntory (although the actua l number of birds was protected by FASS). Suwannee ranked no. 7. Suwannee and Lafayette ranked no. 1 and no. 4, respectively, in broiler inventory. Levy, Gilchrist, Lafayette, and Su wannee ranked 2nd, 3rd, 4th, and 6th, respectively, in dairy production sales value. Figure 9. Animal agriculture in Florida's Lower Suwannee River Basin area (2002). *Animal numbers for these counties were excl uded from the ag census to avoid disclosing data for individual farms.
12Pastureland Pastureland is widespread throughout Floridas Lower Suwa nnee Basin area, and is the most common agricultural land use in each county (Fig. 10). Statewide, in 2002, Alachua ranked no. 12 for land area devoted to pasture. Figure 10. Pastureland acreage in Florida's Lower Suwannee River basin area (2002). Outdoor nurseries Levy County dominated in land area devoted to outdoor nursery production in 2002, with about half of the Lower Suwannee Basin area total (Fig. 11). Alac hua had 17% of the total, and the rest was distributed among 9 other counties for which data were available. No data were reported for Lafayette and Union. Figure 11. Outdoor nursery acreage in Florida's Lower Suwannee River Basin area (2002).
13Irrigation Although the Lower Suwannee Basin averages 50 inches of rainfall per year, uneven distribution can lead to drought periods in the spring and fall. Spring crops are particularly susceptible to water stress, so all vegetable cr ops and many other row crops are irrigated. Both overhead and low-volume (drip) irrigation system s are used, and the primary water source is groundwater. The top three counties in irrigated acreage are Levy, Suwannee, and Alachua (Fig. 12), which is no surprise because these are also th e top three counties in field crop production. These counties plus Gilchrist are the top four agricultural water us ers in terms of freshwater withdrawals (Fig. 12). When comp aring the two maps in Fig. 12, the reader is cautioned that while irrigated acreage is for the entire county, wa ter use data represent on ly the land area within the Suwannee River Water Management District boundary. Therefore, the two maps are not directly comparable for Alachua, Bradford, Je fferson, and Levy counties. Also, the water use data is 2 years older than the irrigated acreage data. Figure 12. Agricultural irrigation water use in Florida's Lower Suwannee River Basin area. *Values shown for Alachua, Bradford, Jefferson, and Levy counties represent only the portion of the county within the SRWMD boundary. Fertilizer consumption Fertilizer application is necessary to ach ieve maximum economic crop yields in the Lower Suwannee Basin. Nitrogen and phosphorus ar e two macronutrients commonly applied in fertilizers. These nutrients provide a positive crop response, but can also degrade water quality if, over the long term, they are transported by leaching or runoff from the application site to surface or groundwater.
14 Nitrogen fertilizer consumption by count y fell into four groups (Fig. 13): Suwannee and Levy consumed more than 3,700 tons of N per year. Gilchrist, Alachua, Union, and Jefferson used between 2,000 and 2,500 tons per year. Madison, Columbia, and Lafayette used between 1,000 and 1,500 tons per year. Hamilton, Bradford, Dixie, and Taylor used less than 1,000 tons per year. Phosphate fertilizer consumption fell into three groups (Fig. 13): Levy and Union consumed 1,000 or more tons of P2O5 per year. Jefferson, Suwannee, Gilchrist, and Alachua used between 600 and 900 tons per year. Columbia, Madison, Hamilton, Lafayette, Brad ford, Dixie, and Taylor used less than 400 tons per year. The amount of fertilizer used within a county is influenced by the amount and type of crops grown, and by the availability of animal manures that may be applied as an alternative source of N and P. It is no surprise that Levy, Suwannee, and Alachua counties are among the largest N and P fertilizer users since they are th e counties with the greatest field crop acreage. Although Union county is small in land area, it is the fourth largest in terms of vegetable production within the Lower Suwannee Basin area. Fe rtilizer use there is relatively high because vegetable crops are intensively fertilized. Figure 13. Nitrogen and phosphorus fertilizer consumption (July 2002 through June 2003) in Florida's Lower Suwannee River Basin area.
15Summary Floridas Lower Suwannee Basin area contains: A population just above one-half million th at is skewed towards Alachua county. Topography ranging from flat to gently rolling. Sandy soils vulnerable to nutrient and agrichemical leaching, especially under conditions of excessive rainfall or irrigation. Mostly rural land that supports pine plan tations, numerous small to medium-sized farms, and a few large farms. Forest, field crop, forage, animal, and nur sery production that is economically important both locally and statewide. More than 75,000 acres of irrigated agriculture. Soils low in natural fertility that require high fertilizer rates to achieve maximum economic yield. Groundwater, surface water, and an ecosy stem in need of environmental protection. Therefore, educating the region s agricultural producers and other citizens about the best ways to manage water and nutrients will be essen tial to maintain water availability and improve its quality in the years to come.