2019_cvr_spine_letter_final_July16.indd

Chapter 2. Fertilizer Management for Vegetable Production in Florida G. D. Liu, E. H. Simonne, K. T. Morgan, G. J. Hochmuth, Shinsuke Agehara, and Rao Mylavarapu BEST MANAGEMENT PRACTICES With the passage of the Federal Clean Water Act (FCWA) in 1972, states were required to assess the impacts of agricultural fertilizer use on surface and ground waters. The FCWA also requires states to identify impaired water bodies and establish the amount of fertilizer nutrient that can enter �� uses) called total maximum daily loads (TMDLs). Water quality TMDLs involving vegetable production are concentrations of nitrate, phosphate, �� entering ground and surface water, while maintaining or increasing economical yields. BMPs are intended to be economically sound, cost effective, �� recognize that BMPs do not aim at becoming an obstacle to vegetable production. Instead, they should be viewed as a means to balance economical vegetable production with environmental responsibility. The BMPs that will apply to vegetable production in Florida are described in the “Agronomic and Vegetable Crop Water Quality/Water Quantity BMP Manual for Florida” produced by the Florida Department of Agriculture and Consumer Services (FDACS). This manual was developed through a cooperative effort between state agencies, water management districts and �� Florida Institute of Food and Agricultural Sciences (UF/IFAS). The manual was adopted by reference in 2006 and by rule in Florida Statutes (5M-8 Florida Administrative Code) and was revised in 2015 (��- waterpolicy.com/ PDFs/BMPs/vegetable&agronomicCrops.pdf). Vegetable �� BMP program, 2) how to join it, 3) how to select the BMPs that apply to their operation and 4) how to meet the requirements, by getting in contact with their UF/IFAS Extension county agent. The vegetable BMPs have adopted all current UF/IFAS-recommended including those for fertilizer and irrigation management (see the new BMP �� fertilizer rates should be used together with proper irrigation scheduling techniques and crop nutritional status monitoring tools (leaf analysis, petiole sap testing). In the BMP manual, adequate fertilizer rates may be achieved by combinations of UF/IFAS recommended basal rates and supplemental fertilizer applications added after leaching by rainfall, when tissue analyses suggest a need for more fertilizer, or when the harvesting season is prolonged. SOILS Vegetables are grown in various soil types throughout the state. These soil types include sandy soils, sandy loam soils, Histosols (organic muck), and calcareous marl soils. Sandy soils make up the dominant soil type for vegetable production in Florida. Vegetables are produced on sandy soils throughout the Florida peninsula and on sandy soils and sandy loams in the panhandle. Sandy soils have some advantages: ease of tillage; production of the earliest vegetable crops; timely production operations but disadvantages as well: leaching mobile nutrients such as nitrogen, potassium and even phosphorus by heavy rain or excessive irrigation. Therefore, sandy soils must be managed carefully regarding fertilization programs and irrigation scheduling. Histosols, calcareous rocky, and marl soils are also important for Florida’s vegetable production. For more information, please see “Soil and Fertilizer Management for Vegetable Production in Florida” at <��>. SOIL PREPARATION A well-prepared planting bed is important for uniform stand establishment of vegetable crops. Previous crop residues and weeds should be plowed down well in advance of crop establishment. A 6- to 8-week period between plowing down of green cover crops and crop establishment is recommended to allow the decay of the residues. Freshly incorporated plant material promotes high levels of damping-off organisms such as Pythium spp. and Rhizoctonia spp. Turning under plant residue well in advance of cropping reduces damping-off disease organisms. Land should be kept disked if necessary to keep new weed cover from developing prior to cropping. �� - cayed roots may create problems in preparing good beds over which mulch will be applied. For more information about soil preparation for commercial vegetable production, see “Soil Preparation and Liming for Vegetable Gardens” at <��. LIMING Current UF/IFAS recommendations call for maintaining soil pH between 6.0 and 6.5 (Table 1); further discussion is in “Soil pH Range for Optimum Commercial Vegetable Production” at <��. If soil pH is too low, liming is needed. A common problem in Florida has been over-liming, resulting in high soil pH tying up micronutrients and phosphorus causing a restriction of their uptake by plants. Over-liming can also reduce the accuracy with which a soil test can predict the fertilizer component of the Crop Nutrient Requirement (CNR). For more information about liming, see “Liming of Agronomic Crops” at <��. Liming can not only adjust soil pH but also provide calcium and magnesium if dolomite, i.e., calcium magnesium carbonate, is used. Irrigation water from wells in limestone aquifers is an additional source of liming material. The combination of liming and use of alkaline irrigation water has resulted in soil pH greater than 7.0 for many sandy soils in Florida. To measure the liming effect of irrigation, have a water sample analyzed for total bicarbonates and carbonates annually, and the results converted to pounds of calcium carbonate per acre. Liming (Table 2), fertilization (Table 3), and irrigation programs are closely related to each other. To maximize �� be made a part of any fertilizer management program. Additionally, using ammoniacal fertilizers can neutralize alkalinity (Table 3) but nitrate fertilizers can increase pH in the root zone due to selective uptake of differentiations by plants. Fertigation with ammonium-N (such as ammonium sulfate) is effective for decreasing soil pH but volatilization may be a concern. /waterpolicy.com