| Florida citrus production is ranked number one in the nation, accounting for 63% of the 371,700 ha production area in the U.S. California, Texas, and Arizona account for 32.5%, 3.3% and 1.6%, respectively. Citrus production in Florida has declined over the past 14 years from 342,077 ha in 1998 to 232,470 ha in 2011 largely due to increased urbanization, hurricanes, citrus canker (Xanthomonas axonopodis) and citrus greening (Liberibacter asiaticus). The uneven rainfall distribution and sandy soils make water and nutrient management extremely difficult. Thus, novel practices termed advanced citrus production systems (ACPS) using higher tree density, dwarfing rootstocks and a modified open hydroponics system (OHS) were developed to accelerate tree growth and bring young trees into production so growers can break-even within a few years of establishing a grove. Several field and laboratory experiments coupled with computer simulations were conducted to compare the performance of the intensively managed drip and microsprinkler irrigation and fertigation systems with conventional grower practices on the Florida Flatwoods and Ridge soils.;The Ridge and Flatwoods field studies revealed higher but not significantly different water uptake with ACPS/OHS compared with grower practices. However, tissue nutrient concentration was greater for ACPS/OHS than the grower practices. In addition, ACPS/OHS practices, particularly on the Ridge, increased soil nutrient retention in the root zone by 60-90% compared with conventional fertigation or granular fertilization. The soil cores indicated greater root length density for ACPS/OHS than grower practice, in the irrigated zones, and in the 0-15 cm soil layer. HYDRUS-2D model, calibrated with field and laboratory data, showed reasonably good agreements between simulated and measured values suggesting that HYDRUS-2D could successfully be used as a tool for irrigation and nutrient management decision support.;Overall, the results underline the importance of using innovative and carefully managed intensive fertigation practices in promoting tree growth and root length density, increasing nutrient and water uptake, and conserving environmental quality while sustaining high citrus yields on Florida’s sandy soils. The results from the field experiments and computer simulations should allay any fears of potential groundwater contamination associated with proper use of the ACPS/OHS practices. |
