Recipient Organization
UNIVERSITY OF FLORIDA
G022 MCCARTY HALL
GAINESVILLE,FL 32611
Performing Department
Soil and Water Sciences
Non Technical Summary
Florida is the second largest producer of vegetables in the USA (USDA-ERS, 2016). Most are grown under intensive management of nutrients and water, usually on sandy textured soils. Approximately 30,000 acres are utilized for tomato production in Florida (USDA-NASS, 2018). Optimization of nutrient and water applications and their use efficiencies is important for minimizing any potential losses of nutrients to the environment, particularly nitrogen (N), in sandy soils. Use of predictive and diagnostic scientific tools such as soil and plant tissue testing are critical for determining the crop requirements of nutrients and recommendations for supplemental nutrient applications for sustainable crop production. Several agricultural BMPs have been identified, developed and implemented for enhancing plant use efficiencies of nutrients such as N in conjunction with 4Rs principles, where soil testing is inherently the first step. For tomato production on sandy soils in Florida, BMPs include: drip irrigation, delivery of N fertilizer applications in small and 13 weekly doses (Jalpa et al., 2018), and plastic mulched beds, crop rotations between tomato seasons, etc., all of which help improve N use efficiency (NUE). This research study evaluates the suitability of controlled-release urea (CRU), applied only once, as an alternative nitrogen (N) fertilizer source to conventional urea (U), which is applied in multiple doses for tomato production. Cover crops will be grown during the intervening periods between seasons, used as N catch crops and also potential N sources for the next season. Information on the effects of controlled-release N fertilizer on a tomato-cover crop rotation system is almost non-existent for Florida soils and production systems.One of the most important BMPs is applying P fertilizer at recommended application rates. However, growers perceive that the current P fertilizer recommendation based on state-recommended soil P test (Mehlich 3, M-3) is insufficient to maximize yield. Growers are reporting positive yield responses to fertilizer P rates above the recommended rates on soils with high M-3 P and have questioned whether the M-3 soil test is appropriate for all Florida soils. Efforts are needed to address the applicability of M-3 test to South Florida by confirming reported yield responses to P application above the M-3 based recommendation and then identifying the underlying reasons and, if needed, modifying the test, interpretation and/or recommendations. These efforts need to be combined with the evolving modern technology and innovations that further improve the water and P use efficiency.Soil boron is found in four different forms- water soluble, absorbed, organically bound, and fixed in clay and mineral lattices. Water-soluble B involves in direct nutrition to the plant, and is therefore of agricultural significance. The water soluble reserves occur predominantly as undissociated, electroneutral boric acid, derived from sediments or plant material which are originally from tourmaline, which is relatively insoluble form of borosilicate.The very small quantities of B that have to be measured and the narrow range between deficiency and toxicity make instrumental determination of B very critical. The high precision required to be able to detect very small differences in the B contents make the method employed very important. Biological methods have no place when a large number of samples are to be analyzed in a limited amount of time. Methods that require a series of operations and lots of handling lead to error magnification and should not be recommended for determining small quantities of B. Therefore, study on use of universal soil extraction method, Mehlich-3 in combination with ICP-OES instrumentation as the most efficient method for soil boron determination becomes critical for high through-put and high volume laboratories where soils can be analyzed with accuracy and consistency.
Animal Health Component
80%
Research Effort Categories
Basic
(N/A)
Applied
80%
Developmental
20%
Goals / Objectives
Both nitrogen (N) and phosphorus (P) are major nutrients required for sustainability of agricultural production. At the same time both these nutrients can potentially have a negative impact on the environment, when not managed scientifically. So, employing effective field management techniques such as principles of 4Rs, application of P-Index as risk assessment tool for P are as equally critical as the determination of the crop requirements of N and P for optimal production using scientific tools such as soil and tissue testing. Crop response to applied N is usually determined through research studies correlating the response to yields. However, information on accurate N requirement of various crops is generally limited. Assessment of crop uptake, inefficiencies and environmental losses are required to ensure a realistic N recommendation to the crops grown in different regions of Florida. Using controlled relases N fertilizers as sources is another key element in this process to enhance uptake and minimize losses. Similarly, tools such as the Florida P-Index (PI) should be field validated and revised for preventing P losses to the environment through runoff and leaching. Following are the major objectives of this project-1. to determine N and P and other requirements of agronomic and horticultural crops for optimum economic yields,2. to improve field management techniques through controlled or slow release sources, managing timing, amount and method of application,and3. to determine effects of cover crops in enhancing soil health and productivity4. Determine soil B using optimized analytical method for consistency and accuracy for commercial and high through-put labs for efficiency and automation.
Project Methods
1.Nitrogen Efficiency Using Controlled-Release Sources and Cover Crops in Drip Irrigated Tomato Cropping Sequence Under Plastic MulchThe proposed project will be conducted over two years at the UF/IFAS Plant Science Research and Education Unit in Citra, Florida. Both years will have acrop sequence of fall tomato-winter rye-spring tomato-sorgum-sudan. CRU fertilizers with different release durations of 60 (CRU-60), 75 (CRU-75) and 90 (CRU-90) days will be used in order to establish the optimum N release rate for determining crop N requirement. These will be compared to traditional soluble-U applied through fertigation at 13 equal doses throughout the crop season. The study will be laid out in a randomized complete block design with three replications of 10 fertilizer treatments: Control (no N fertilizer application); U (applied at N rates of 140, 168, and 224 kg N ha-1); CRU-60 and 75 (control release fertilizer with a release duration of 60 or 75 days, applied at N rates of 140, 168, and 224 kg N ha-1); CRU-90 (control release fertilizer with a release duration of 90 days, applied at N rates of 140, 168, and 224 kg N ha-1). The plots are 9.1 meters (m) long with 6 beds, with each bed 1.8 m wide. The CRU fertilizer treatments will be broadcast before bed formation. The plots will be rototilled in order to incorporate the CRU fertilizer into the soil. The beds will be formed, fumigated, and a single line of drip irrigation tape will be laid. Beds will then be covered with a white plastic mulch. Tomatoes will be planted at 0.6 m spacing.2.Phosphorus Bioavailability Analyses for Improved Use Efficiency and Sustainability of Fresh ProduceThe present study is designed to evaluate the effects of P fertilizer application rates on alkaline soils of south Florida and bed geometry on plant growth and yield while probing pertinent soil, hydrologic and management-related factors that could elucidate any discrepancies observed between M-3-based recommendations and crop response. The proposed study will help answer the following questions: 1) is there a statistically significant yield response to P fertilization above the M3P-based recommended rates; 2) is P primarily associated with Ca rather than Al in these soils, possibly resulting in high M3-P/total P ratio, lack of WEP-PSR relation, and a crop response to P at high M3-P values?; 3) can compact beds increase bioavailability of P and its use efficiency due to reduced flooding (runoff, soil saturation) and leaching of P below the bed?; 4) can compact beds sustain yields with M3P based recommendation?; and 5) is it feasible to develop alternative soil, water, and nutrient management practices, using study results, to sustain yields on conventional and/or compact beds without increasing environmental P losses? Tomato response to a range of P application rates applied on compact and conventional beds will be assessed on a poorly drained "flatwoods" soil area that has been determined to have high pH, Ca, and M-3 P. The soils in the area (mainly Aquods, Aqualfs, and Aquents) are prevalent in Florida and are used extensively for vegetable production. We will examine the correlation between water and nutrient dynamics (P transformations and flux) and crop response at this site.3. Soil boron determination will be made using Mehlich-3 and boiling water and extraction methods and analyzing on ICP instrument. The soils for this study will be assembled from a pool of soils from the national proficiency testing and archived soil samples post-analyses at the extension soil testing laboratory. Soils will be divided into calibration and validation groups at approx. 70:30 respectively. Initially, the proficiency samples will be used to verify the method and the steps for consistency and accuracy. Laboratory QA/QC will be implemented for duplicates, blanks, blinds, spikes, LCS, etc. Parameters such as water, filter paper and labware (glass and plastic) will be studied for potential contamination and will be removed. Once the background noise is successfully minimized, the extraction methods and the instrument will be studied for consistency and accuracy. Once confirmed, random extension soil samples received directly from the clients will be used for testing- calibration and validation.