Florida is located in a subtropical climate zone that normally receives 48 to 60 inches of rainfall annually. This rainfall amount is adequate to meet the requirements of most citrus cultivars. However, annual rainfall distribution does not usually satisfy peak seasonal demands during critical fruit set and early fruit development. During these phenological periods, good irrigation management is critical to reduce stress and the associated young fruit drop resulting in yield reduction. Historically, irrigation types used for tree fruit production have been water wagons, surface flood, subsurface or seepage, perforated pipe, and overhead high-volume sprinkler. Over the past 20 years, nearly all Florida citrus and other tree fruit irrigation have been converted from high-volume sprinkler to low-volume under-tree microsprinkler irrigation (Boman, 2002).
World production of all citrus cultivars totaled 82 million tons in the 2007 crop year (Florida Agricultural Statistics Service, 2007). The main centers of citrus production in the United States are located in Florida (67%), California (28%), Texas (4%), and Arizona (1%) and total 9.4 million tons or 13% of world production. Florida citrus production in 2006–2007 was orange (Citrus sinensis) (80%), grapefruit (C. paradisi) (17%), and tangerine (C. reticulata) (3%). Citrus area in Florida was highest at over 941,000 acres in 1970 and then declined to less than 624,000 acres in 1985 as a result of the effect of three successive freezes (Florida Agricultural Statistics Service, 2007). Since the mid-1980s, the Florida citrus area has rebounded to nearly 857,000 acres in 1998. Citrus area has declined over the past 8 years to 621,373 acres as a result of control of citrus canker (caused by Xanthamonus axonopodis), greening (huanglongbing caused by Laberibacter asiaticus) diseases, and urbanization.
With a crop value of $1.362 billion in 2006–2007, citrus is one of the most important horticultural crops in Florida. Just over 75% of Florida citrus production is on sandy Spodosols or Alfisols with a spodic or argillic horizon at less than 1 m below the soil surface (Florida Agricultural Statistics Service, 2007). These “flatwood soils” are found in the southwest flatwoods (Hendry, Collier, Desoto, Hardee, Manatee, and Hillsborough counties) and eastern county (St. Lucie, Indian River, Okeechobee, and Martin counties) citrus production areas. Because these soils are sandy, nutrient and water-holding capacities are quite low (Obreza and Collins, 2002; Obreza et al., 1997). Many of these soils have a hardpan composed of aluminum (Al) and iron (Fe) “cemented” together with organic matter or a subsurface layer of loamy material (a mixture of mostly clay and sand with little silt) that have higher water-holding capacity and lower saturated hydraulic conductivity, thus increasing drainage time required. The reduction in drainage caused by these soil horizons can lead to temporary increases in soil water content after rain or excessive irrigations, limiting nutrient leaching. Drainage, the presence or absence of impermeable soil diagnostic horizons, and whether the citrus grove is bedded all have considerable influence on citrus root distribution. Because of the need for adequate drainage, these soils are bedded for commercial citrus production, often with additional ditching to remove excess water. The shallow root system is restricted to the upper 30 to 45 cm of soil with approximately one-third of the root system extending out to the edge of the bed (Bauer et al., 2005). The remainder of the root system is located toward the center of the bed.
Approximately 25% of Florida citrus is grown in the central Florida ridge area (Polk, Highlands, and Lake counties) on Entisols, which are characterized by uncoated sand (i.e., sands striped of Al or Fe compounds that increase nutrient-holding capacity) with low organic matter content, therefore have very limited water- and nutrient-holding capacities (Obreza and Collins, 2002; Obreza et al., 1997). These “ridge soils” are deep and well-drained. Root zones on these Entisols are not restricted by soil horizons and are typically 90 cm deep or greater (Morgan et al., 2007).
Tropical tree fruit crop production [e.g., avocado (Persea americana) and mango (Mangifera indica)] is restricted to ≈3116 ha in Dade and Brevard counties as a result of frost potential elsewhere in the state (Florida Agricultural Statistics Service, 2005). Soils in these lower coastal counties of Florida are dominated by rocky calcareous soils or thin sand soils overlying limestone. These soils are highly porous with low water-holding capacities during periods of low rainfall but can be poorly drained during Florida's summer rainy season because of the proximity to the water table. Temperate fruit crops [e.g., peach (Prunus persica) and blueberry (Vaccinium corymbosum)] production is located in north–central Florida centered in Marion County. Soils here are sandy Alfisols with higher clay contents and thus water-holding capacities than the soils described thus far; however, irrigation management remains key to optimum productivity.
Nutrient and agricultural chemical movement into surface water and groundwater has become a greater concern in Florida over the past two decades. To preserve water quality within the state, best management practices (BMPs) have been developed for irrigation. Irrigation schedules should focus on optimum crop productivity by encouraging deep rooting and reducing leaching impacts on water quality. The remainder of this review illustrates many irrigation BMPs for citrus production in Florida; however, the application of the BMPs may be applied to perennial fruit crops cultivated in Florida.
Allen, R.G., Pereira, L.S., Raes, D. & Smith, M. 1998 Crop evapotranspiration—Guidelines for computing crop water requirements United Nations, Food Agr. Organization, Irr. Drainage Paper No. 56
Baker, J.M. & Allmaras, R.R. 1990 System for automating multiplexing soil moisture measurement by time-domain reflectometry J. Soil Sci. Soc. Amer. 54 1 6
Bauer, M., Castle, W.S., Bowman, B.J. & Obreza, T.A. 2005 Economic longevity of citrus trees on Swingle citrumelo rootstock and their suitability for soils in the Indian River region Proc. Florida State Hort. Soc. 118 15 18
Boman, B.J. 1990 Clogging characteristics of various microsprinkler designs in a mature citrus grove Proc. Florida State Hort. Soc. 103 327 330
Boman, B.J. 2002 Efficiency, uniformity, and system evaluation 399 414 Boman B.J. Water and Florida citrus: Use, regulation, systems, and management Univ. Florida Inst. Food Agr. Sci. Press Gainesville, FL
Bouyoucos, G.J. & Mick, A.H. 1948 A comparison of electric resistance units for making a continuous measurement of soil moisture under field conditions Plant Physiol. 23 532 543
Castel, J.R., Bautista, I., Ramos, C. & Cruz, G. 1987 Evapotranspiration and irrigation efficiency of mature orange orchards in ‘Valencia’ (Spain) Irrig. Drain. Syst. 3 205 217
Castel, J.R. & Buj, A. 1992 Growth and evapotranspiration of young, drip-irrigated clementine trees Proc. Intl. Citriculture 2 651 656
Dean, T.J., Bell, J.P. & Baty, J.B. 1987 Soil moisture measurement by an improved capacitance technique. Part I. Sensor design and performance J. Hydrol. (Amst.) 93 67 78
Florida Agricultural Statistics Service 2005 Commercial citrus inventory 2005 Florida Department of Agriculture and Consumer Services Tallahassee, FL
Florida Agricultural Statistics Service 2007 Commercial crop statistics 2007 Florida Department of Agriculture and Consumer Services Tallahassee, FL
Florida Department of Environmental Protection 2005 Reuse inventory report 22 Oct. 2008 <http://www.dep.state.fl.us/water/reuse/inventory.htm>.
Haman, D.Z., Smajstrla, A.G. & Pitts, D.J. 2005 Efficiencies of irrigation systems used in Florida nurseries Inst. Food Agr. Sci., Univ. Florida. Bul. 312
Hoffman, G.J., Oster, J.D. & Alves, W.J. 1982 Evapotranspiration of mature orange trees under drip irrigation in an arid climate Trans. Amer. Soc. Agr. Eng. 25 992 996
Jia, X., Swancar, A., Jacobs, J.M., Dukes, M.D. & Morgan, K.T. 2007 Comparison of evapotranspiration rates for flatwoods and ridge citrus Trans. Amer. Soc. Agr. Eng. 50 83 94
Koo, R.C.J. 1978 Response of densely planted ‘Hamlin’ orange on two rootstocks to low volume irrigation Proc. Florida State Hort. Soc. 91 8 10
Martin, E.C., Hla, A.K., Waller, P.M. & Slack, D.C. 1997 Heat unit-based crop coefficient for grapefruit trees J. Appl. Eng. Agr. 13 485 489
Martínez-Cob, A., Playán, E., Asce, M., Zapata, N., Cavero, J., Medina, E.T. & Pulg, M. 2008 Contribution of evapotranspiration reduction during sprinkler irrigation to application efficiency J. Irrig. Drain. Eng. 134 745 756
Maurer, M.A., Davies, F.S. & Greatz, D.A. 1995 Reclaimed wastewater irrigation of reset ‘Marsh’ grapefruit trees Proc. Florida State Hort. Soc. 108 93 99
Morgan, K.T., Obreza, T.A., Scholberg, J.M.S., Parsons, L.R. & Wheaton, T.A. 2006a Citrus water uptake dynamics on a sandy Florida Entisol Soil Sci. Soc. Amer. J. 70 90 97
Morgan, K., Beck, H., Scholberg, J. & Grunwald, S. 2006b In-season irrigation and nutrient decision support system for citrus production Proc. World Congr. Computers Agr. Natural Resources 1 649 654
Morgan, K.T., Obreza, T.A. & Scholberg, J.M.S. 2007 Characterizing orange tree root distribution in space and time J. Amer. Soc. Hort. Sci. 132 262 269
Morgan, K.T., Parsons, L.R., Wheaton, T.A., Pitts, D.J. & Obreza, T.A. 1999 Field calibration of a capacitance water content probe in fine sand soils Soil Sci. Soc. Amer. J. 63 987 989
Morgan, K.T., Wheaton, T.A., Castle, W.S. & Parsons, L.R. 2008 Effects of reclaimed municipal waste water on horticultural ratings, fruit quality, and soil and leaf mineral content of citrus grown in central Florida HortScience 43 459 464
Morgan, K.T., Wheaton, T.A., Castle, W.S. & Parsons, L.R. 2009 Response of citrus to irrigation, nitrogen rate and application method HortScience 44 145 150
Obreza, T.A. 2004 Maintenance guide for Florida microirrigation systems Coop. Ext. Serv., Inst. Food Agr. Sci., Univ. Florida Cir. 1449 22 Oct. 2008 <http://edis.ifas.ufl.edu/SS436>.
Obreza, T.A. & Collins, M.E. 2002 Common soils used for citrus production in Florida Inst. Food Agr. Sci., Univ. Florida. Sl.193 19 Nov. 2008 <http://edis.ifas.ufl.edu/pdffiles/SS/SS40300.pdf>.
Obreza, T.A., Pitts, D.J., Parsons, L.R., Wheaton, T.A. & Morgan, K.T. 1997 Soil water-holding characteristic affects citrus irrigation scheduling strategy Proc. Florida State Hort. Soc. 110 36 39
Parsons, L.R. & Morgan, K.T. 2002 Management of microsprinkler systems for Florida citrus Coop. Ext. Serv., Inst. Food Agr. Sci., Univ. Florida HS204 19 Nov. 2008 <http://edis.ifas.ufl.edu/HS204>.
Parsons, L.R., Wheaton, T.A. & Castle, S.W. 2001 High application rates of reclaimed water benefit citrus tree growth and fruit production HortScience 36 1273 1277
Parsons, L.R., Wheaton, T.A., Castle, W.S., Morgan, K.T., Scholberg, J.M.S., Rockwood, D.L., Snyder, G.H. & Jackson, J.L. 1999 Water Conserv II annual report 1998–99 Univ. Florida, Citrus Res. Educ. Ctr Immokalee, FL
Rogers, J.S., Allen, L.H. & Calvert, D.V. 1983 Evapotranspiration from a developing citrus grove in a humid climate Trans. Amer. Soc. Agr. Eng. 26 1778 1783
Rogers, J.S. & Bartholic, J.F. 1976 Estimated evapotranspiration and irrigation requirements for citrus Soil Crop Sci. Soc. Florida Proc. 35 111 117
Scholberg, J.M.S., Parsons, L.R., Wheaton, T.A., McNeal, B.L. & Morgan, K.T. 2002 Soil temperature, nitrogen concentration, and residence time affect nitrogen uptake efficiency in citrus J. Environ. Qual. 31 759 768
Smajstrla, A.G. & Koo, R.C. 1986 Use of tensiometers for scheduling of citrus trickle irrigation Proc. Florida State Hort. Soc. 99 51 56
Smajstrla, A.G. & Koo, R.C.J. 1984 Effect of trickle irrigation methods and amount of water applied on citrus yield Proc. Florida State Hort. Soc. 97 3 7
Smajstrla, A.G. & Pitts, D.J. 1997 Tensiometer service, testing and calibration Inst. Food Agr. Sci., Univ. Florida, Coop. Ext. Serv. Bul. 319
Thomson, S.J. & Ross, B.B. 1996 Model-based irrigation management using a dynamic parameter adjustment method Comput. Electron. Agr. 14 269 290
Water Reuse Work Group 2003 Water conservation initiative 22 Oct. 2008 <http://www.dep.state.fl.us/water/waterpolicy/docs/WCI_2002_Final_Report.pdf>.
Wheaton, T.A., Parsons, L.R., Castle, W.S., Morgan, K.T. & Jackson, J.L. 1998 Water Conserv II annual report 1997–98 Univ. Florida, Citrus Res. Educ. Ctr Immokalee, FL