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This new 7-page publication of the UF/IFAS Food and Resource Economics Department explores the potential of using bagasse, a dry and fibrous residue of sugarcane left after the sugar juice extraction, as a nutrient source to potentially reduce inorganic fertilizer inputs in the sugarcane production system. Information provided in this article will be useful to commercial sugarcane growers, crop consultants, and fertilizer manufacturers in helping them explore alternative fertilizer options. This paper provides important and timely information for the target audiences, considering the recent, rapid rise in fertilizer prices. Written by Jehangir H. Bhadha, Nan Xu, Naba R. Amgain, Abul Rabbany, Trent D. Blare, Fredy H. Ballen, and Stewart Swanson.https://edis.ifas.ufl.edu/fe1121

To trace the phosphorus (P) and potassium (K) content in flooded rice (Oryza sativa L), 14 rice cultivars commonly grown in the Southern United States were evaluated for their P and K concentration in tissue and grain. Field experiments were conducted at two locations in Everglades Agriculture Area (EAA), where flooded rice was cultivated on organic Histosols. Soil pH and Mehlich-3 phosphorus (M3P) were significantly different between locations. At Site I, soil pH, M3P, and Mehlich-3 potassium (M3K) varied in the range of 6.8–7.1, 21.4–36.4 mg kg−1, and 53.9–151.0 mg kg−1, respectively. At Site II, soil pH, M3P and M3K varied in the range of 6.9–7.3, 11.2–20.5 mg kg−1, and 64.8–104.1 mg kg−1, respectively. Stem potassium was the only measured parameter that was significantly different among rice cultivars at both sites. At Site I and Site II, stem K ranged from 14.2–26.6 mg kg−1 and 10.4–19.4 mg kg−1, respectively. No significant difference in yield among cultivars was observed at Site I, whereas Site II had a significant difference in yield among cultivars. At Site I and Site II, yields ranged from 3745–7587 kg ha−1 and 2627–6406 kg ha−1, respectively. None of the cultivars ranked consistently in the same top and bottom position for each measured parameter. Total phosphorus (TP) concentration was highest in grain, whereas total potassium (TK) concentration was highest in the stem. Results suggest incorporation of rice stem into the soil could potentially add fertilizer back to the soil which helps in fertility management.

The addition of organic byproducts to soils is a vital source of essential nutrients for plant uptake. To reuse the nutrients effectively, there is a need to estimate the release patterns of nutrients from the byproducts. This study aimed to investigate the release patterns of nutrients [nitrogen (N), phosphorus (P), and potassium (K)] from bagasse, a sugarcane milling byproduct, at two soil depths (surface at 0 cm vs. buried at 15 cm) in sugarcane and fallow fields on two soil types (Histosols vs. Spodosols) in Florida. In addition, field incubation studies were conducted using the mesh bag technique for one year of sugarcane production. The nutrient release patterns and bagasse decomposition rates were determined under each scenario. The results indicated that bagasse decomposed faster when buried (totally decomposed after approximately 450 days) than when placed on the soil surface (about 50% remained after 450 days) in both sugarcane and fallow fields on Spodosols and Histosols. Bagasse decomposed faster in Histosols compared to Spodosols. N and P showed net immobilization after approximately one month of bagasse application when buried, which indicated additional N and P fertilizers should be considered to meet crop demand. K presented no immobilization, with a rapid initial release in Spodosols and a gradual release in Histosols.

The global demand for P fertilizers has been significantly increasing, resulting in higher costs and environmental concerns associated with eutrophication. Fertilizer expenses and environmental risks can be reduced through the implementation of sustainable strategies. This new 6-page publication of the UF/IFAS Horticultural Sciences Department compiles several strategies to improve the utilization of P fertilization in lettuce grown in the Everglades Agricultural Area.https://edis.ifas.ufl.edu/hs1423

The efficient use of phosphorus (P) fertilizers is very important in South Florida so that the environmental impact is minimal while meeting crop demand. To ensure that this is accomplished, an upd...

Sustainable production in the Everglades Agricultural Area (EAA) is confounded by decreasing soil depth and high annual rainfall. Formerly a sawgrass marsh, Histosols predominate much of the EAA an...

In South Florida, approximately 11,000 ha of rice is grown every summer on highly organic histosols. With no added fertilizer inputs of phosphorus (P) or nitrogen (N) as part of the cultivation program, growing flooded rice has the potential to reduce nutrient fluxes from soils to surface water and limit its losses to the water column. Changes in soil redox potential (Eh) will play an important role in the availability of P and nitrate (NO3−) concentration within the groundwater, which ultimately drives the direction of diffusive fluxes across the soil–water interface. The objective of this study was to measure vertical Eh and groundwater concentrations of P and NO3− from commercial flooded rice fields and estimate diffusive fluxes across the soil–water interface. Results indicate that Eh was depth dependent, where deeper soils (30 cm deep) were slightly more anaerobic (mean − 162 mV) than shallow soils (15 cm deep) (mean − 144 mV). Groundwater P concentrations ranged between 0.38 and 1.09 mg L−1 in deep soils (up to 60 cm) and 0.018–0.608 mg L−1 in shallow soils (up to 40 cm). Groundwater NO3− concentrations ranged between 0.065 and 0.64 mg L−1 in deep soils (up to 60 cm) and 0.055–0.499 mg L−1 in shallow soils (up to 40 cm). Diffusive fluxes were mostly positive, which meant they flowed from shallow groundwater to the water column. Phosphorus fluxes were as high as 0.134 mg m−2 d−1 observed in 60-cm deep soils, whereas NO3− fluxes were as high as 0.12 mg m−2 d−1 observed in 40-cm shallow soils. Diffusive fluxes of P and NO3− from flooded rice fields were relatively lower compared to other hydrologic systems.

Soil loss due to subsidence is a major concern in the Everglades Agricultural Area (EAA) of South Florida. Summer is typically the fallow season in the EAA, and soil loss due to oxidation and erosion is significant. Flooding and cover cropping are common practices being adopted to conserve soil, reduce weed pressure, and enhance soil health in the EAA. Cover crops also increase the microbial biomass which are the key drivers of soil function. The objective of this study was to determine the effect of (i) fallow, (ii) dry rice as a cover crop, (iii) flooded fallow, and (iv) flooded rice as a cover crop on soil health indicators and microbial community and diversity within the EAA. Baseline (pre-planting) soil samples were collected from all fields before the application of different treatments and post-harvest soil samples were collected after rice was cut and tilled into the soil surface. Microbial community composition was determined using 16S rRNA gene amplicon and fungal ITS gene amplicon sequencing. Soil bulk density decreased, and cation exchange capacity (CEC) increased in all farming practices including fallow fields. Results showed flooded fallow, flooded rice, and rice planting increased maximum water holding capacity (MWHC) and soil protein and decreased total potassium (TK). Bulk soil microbial communities responded surprisingly quickly to the applied treatments. Taxonomic composition of prokaryotic and fungal communities at the phylum level revealed visible shifts in microbial communities in response to the treatments. Instead of leaving field fallow, planting rice or flooding is a better strategy to improve soil health.

The addition of agricultural by-products to mineral soils has the potential to improve crop production. This study aimed to determine the effects of the readily available sugarcane (Saccharum officinarum) milling by-product bagasse as a soil amendment on yields of sugarcane grown on a sandy Entisol of South Florida. The field trial was conducted on a commercial sugarcane farm for three annual crop cycles (plant cane and two ratoons). Four treatments including 5 cm bagasse (85 ton ha−1), 10 cm bagasse (170 ton ha−1), 10 cm bagasse (170 ton ha−1) plus 336 kg ha−1 ammonium nitrate, and a control (without bagasse and ammonium nitrate) were evaluated. Results indicate that one single application of bagasse increased sugarcane biomass and sugar yield by approximately 23% in the plant cane year. A higher application rate of bagasse (10 cm of bagasse) was recommended since it had a longer effect on increasing sugarcane biomass and sugar yield. Bagasse application enhanced silicon (Si) supply and increased Si plant nutrition. However, the effects of bagasse on the other leaf nutrients were not significant.

Most agricultural soils worldwide present limited availability of phosphorus (P) and crops require supplemental application of P fertilizers. Due to the economic and environmental concerns derived from the use of P fertilizers, identifying and breeding P-efficient lettuce (Lactuca sativa L.) cultivars is imperative for the reduction of production costs and implementation of more sustainable practices. Phosphorus use efficiency (PUE) remains unexplored in lettuce. In this research, 66 lettuce genotypes of six morphological types were evaluated between standard recommended P rate (202 kg·ha–1 of P2O5) and half-P rate (101 kg·ha–1 of P2O5). Lettuce genotypes were tested in two field experiments conducted during the 2017-2018 and 2019-2020 growing seasons in the organic soils (Histosols) within the Everglades Agricultural Area of South Florida. Head weight, marketability, tissue P concentration, soil total-P concentration, and soil extractable P were measured. Genetic variation was detected for PUE within romaine, crisphead, butterhead, Latin, and loose leaf. Eight genotypes were found to produce similar or higher head weight and good marketability when grown in the half-P rate compared to the standard P rate. No correlations were detected between head weight and tissue P concentration, indicating possible variation in P uptake and utilization on the tested lettuce genotypes. A significant, positive correlation was observed for soil total-P and soil extractable P, indicating that the increase in total P concentration of Histosols resulted in higher availability of P to plants. Lettuce genetic variation for PUE may allow further development of P-efficient cultivars for conventional and alternative production systems. More comprehensive investigations must be conducted to elucidate the genetic mechanisms controlling PUE in lettuce.

Stormwater treatment areas (STAs) are constructed wetlands established to capture phosphorus (P) from agricultural runoff before reaching the Florida Everglades. Retained P is primarily stored in wetland soils and sediments generated through a collection of interrelated physical, chemical, and biological processes. The amount of P and other elements (Al, Ca, Cu, Fe, Mg, Mn, Pb, and Zn) retained in the flocculent (floc) and recently accreted soil (RAS) horizons from a relic agricultural ditch within Cell 4S of STA-1E were compared with the surrounding marsh soils (upstream and downstream sites of the ditch). The amount of P retained in the ditch was significantly greater than the surrounding marsh soils and for all the elements in the floc horizon and five of the nine elements in the RAS horizon, suggesting that different processes or process rates influenced accumulation. Phosphorus species in the floc and RAS sediment horizons were identified and quantified using 31 P nuclear magnetic resonance (NMR) spectroscopy and total P determined by microwave plasma-optical emission spectroscopy. In general, P forms were dominated by orthophosphate, sugar phosphates, nucleotides, DNA, and pyrophosphate, with varying relative abundances of species. Total P concentration significantly decreased from upstream to downstream of the ditch by an average of 28 and 35% for floc and RAS soils, respectively. The relatively high P accrual rate within the ditch suggested that relic ditches perpendicular to flow could reduce P transport to downstream soils and sediments and, in turn, help maintain low P levels in overlying water.

The Florida Everglades ecosystem represents a significant wetlands area and serves as a terrestrial carbon reservoir mediated in large part by microorganisms. Shotgun metagenome sequencing provides a snapshot of microbial diversity and the frequency of metabolic and functional gene content. Here, we present an analysis of 20 sediment samples collected from the Arthur R. Marshall Loxahatchee National Wildlife Refuge to characterize the taxonomic and functional potential of the microbial and viral communities, and reconstructed metagenome-assembled genomes. A total of 122 medium-quality and 6 high-quality MAGs are reported, three of which likely represent a novel species within the class Dehalococcoidia.The most abundant phyla of bacteria and archaea were Proteobacteria and Euryarchaeota, respectively. Caudovirales was the most abundant viral order. Significant differences in taxonomic composition and diversity were observed among collection sites. Additionally, water samples were analyzed for pH, total nitrogen, total organic carbon, elements (P, K, Mg, Fe, Mn, Pb, Ca, S), chloride, electric conductivity, orthophosphate, nitrate, and ammonia, while the sediment samples were analyzed for carbon, nitrogen, and pH. Differences in measured aquatic and sediment analytes revealed significant correlations with numerous phyla. Significant correlations were observed between estimated gene frequencies of both aquatic and sediment analytes, most notably between kup/kdpB and dsrA/cysC with potassium and sulfur, respectively, as well as phoD/phnX and cysC with pH. Together, these data provide an important view into the functional and metabolic potential encoded within the sediment microbial communities in the Florida Everglades.

Evaluating changes in soil properties associated with flooded fields during the summer months in the Everglades Agricultural Area (EAA) provides us an opportunity to assess the effect of soil management associated with flooded versus dry-fallow field conditions on Histosols. This information will be beneficial to current and potential growers farming flooded rice in south Florida, as well as Extension agents who work on rice and soil conservation agencies such as the USDA Natural Resources Conservation Service (NRCS). This new 6-page publication was written by Jehangir H. Bhadha, Jay Capasso, Abul Rabbany, Nan Xu, and Matthew VanWeelden, and published by the UF/IFAS Department of Soil and Water Sciences.https://edis.ifas.ufl.edu/ss697

Phosphorous (P) loads from anthropogenic sources increase eutrophication and reduce water quality. This study tested the management of two floating aquatic vegetation (FAV) species—water hyacinth (Eichhornia crassipes (Mart.) Solms)) and water lettuce (Pistia stratiotes L.)—and introduced flow facilitated by hydraulic pumps in reducing P loads exiting agricultural drainage ditches. The experimental design consisted of four treatment ditches equipped with hydraulic pumps to circulate farm canal water through the ditches prior to discharge. Treatment ditches 2 and 3 contained FAV that was physically introduced while treatment ditches 1 and 4 did not. In addition, two control ditches (ditches 5 and 6) were managed without hydraulic pumps or introduced FAV. Introduced flow was found to cause significant differences in total P, total dissolved P, and soluble reactive P concentration (p

Phosphorus is a critical water quality indicator of farm drainage systems. In South Florida, rice (Oryza sativa L.) cultivation has the potential to reduce phosphorus concentration in drainage water through crop uptake under varying flooding systems. A two-year study was conducted to assess drainage water quality under four different flooding systems conventionally used for rice production – 15 cm continuous flood; 5 cm continuous flood; 15 cm with midseason drawdown; and 5 cm with midseason drawdown. In the first growing season, 15 cm continuous flood treatment had the highest reduction of total phosphorus and particulate phosphorus concentrations in drainage water. However, in the second growing season, we did not observe significant differences among water treatments, which was likely due to the release of phosphorus from other sources like soil and rice straw to the water column which masked treatment effects. On average, in both years, all flood treatments reduced total phosphorus concentrations by 42 ± 8% between inflow and outflow water. No phosphorus fertilizer was added and with each harvest, rice grain potentially removed 15.7 ± 3 kg phosphorus ha−1. The results indicate that rice cultivation in fertile soils can successfully reduce phosphorus concentrations in drainage water under well managed water-flow conditions.

Agricultural by-products applied as soil amendments have the potential to improve crop production on low organic matter (OM) soils. This two-year study investigated the use of two readily available...

The addition of organic residues to sand soils can improve soil properties and sugarcane productivity. However, biochar use can have variable effects on crops, and few studies have evaluated the effect of mill ash applications on sand soils. This study aimed to determine the effect of mill ash, and three biochars on yields of sugarcane grown on sand soils of South Florida near the Everglades Agricultural Area (EAA). Nine treatments and a control were evaluated. Treatments consisted of mill ash (AS) and biochars produced from hardwood yard waste (HY), horse barn shavings (HM), and rice hulls (RH) incorporated at 1% and 2% (by weight) prior to the plant-cane crop of a lysimeter experiment that extended for two crop cycles. A standard practice treatment of mill ash applied at 6% was also included. Results show that mill ash applied at 6% and 2% (AS6 and AS2), and rice hulls biochar applied at 2% (RH2) produced significantly greater biomass and sucrose yields compared with the control in the plant-cane and the first-ratoon crops. Soil silicon concentrations increased with AS and RH in the plant-cane crop, which may have contributed to improved yields. Treatments AS6 and RH2 may have also increased sugarcane yields through improved soil properties. Our results show that mill ash and rice hulls biochar amendments can potentially improve sugarcane yields on sand soils near the EAA.

This 5-page document describes the main features of tapegrass and summarizes important habitat requirements for its growth and restoration. Written by Mohsen Tootoonchi, Lyn A. Gettys, and Jehangir H. Bhadha, and published by the UF/IFAS Agronomy Department, September 2019. http://edis.ifas.ufl.edu/ag437

The purpose of this study was to evaluate the influence of suspended particulates on P loading captured during a single storm event. The Everglades Agricultural Area of Florida comprises 280,000 ha of organic soil farmland artificially drained by ditches, canals, and pumps. Phosphorus (P)-enriched suspended particulates in canals are susceptible to transport and can contribute significantly to the overall P loads in drainage water. A settling tank experiment was conducted to capture suspended particulates during tropical storm Isaac in 2012 from three farms approximately 2.4 to 3.6 km2 in size. Farm canal discharge water was collected in a series of two 200-L settling tanks over a 7-day drainage period, during tropical storm Isaac. Water from the settling tanks was siphoned through Imhoff settling cones, where the suspended particulates were allowed to settle and collected for P fractionation analyses, and compared to intact sediment cores collected from the canals. The discharged suspended particulates contained higher organic matter content, total P, and labile P fractions compared to the drainage canal sediments. Based on the equilibrium P concentrations, drainage canal sediments behave as a source of P to the water column. A 7-day continuous drainage event exported 4.7 to 11.1 t of suspended solids per farm, corresponding to 32 to 63 kg of particulate P being lost to downstream ecosystems. Drainage associated to this single 7-day storm event exported up to 61 % of the total annual farm P load. It is evident from this study that short-term, high-intensity storm events can skew annual P loads due to the export of significantly higher suspended particulate matter from farm canals. Exported particulates rich in P, if captured and replenished back on farmlands, would be a sustainable farming practice that can provide a supplemental source of nutrients.

Conventional cropping systems on sandy soils require continuous application of large amounts of external nutrients and irrigation water yet remain vulnerable to loses of these inputs. Within the state of Florida, need exists to provide farmers with economically viable alternatives that harness ecological processes and improve soil health and biodiversity. Cover crops are proving to be vital in the development of soil health. As part of this study we conducted a comprehensive on-farm assessment involving nine collaborative growers (ten farms) across the state; with each individual farm following its unique cover-cropping practice. Our goal was to shadow their practice and determine its effect on soil health indicators such as soil pH, bulk density (BD), maximum water holding capacity (MWHC), organic matter (OM), active carbon, cation exchange capacity, soil protein, Total Kjeldahl nitrogen (TKN), total phosphorus (TP), Mehlich-3 P (M3P) and potassium (M3K). Compared to fallow, soil OM, MWHC, and soil protein showed increases in cover crop fields for most farms, which presented a positive change towards building up soil health. Although soil TKN level was significantly decreased due to cover crops, soil protein level building up over time was the most positive change for soil health. M3K decreased in cover-crop fields, which indicated that supplementary K would be necessary prior to planting subsequent cash crops.

The debates about the extent to which phytoplankton in freshwater ecosystems are regulated by top-down or bottom-up forces have been ongoing for decades. This study examines the effects of bottom-up and top-down factors on the phytoplankton functional groups in a eutrophic lake. Phytoplankton and zooplankton were sampled and physical-chemical variables measured from May 2019 to October 2019 in Lake Hulun, China. Approximately 43 phytoplankton species were observed and grouped into 23 functional groups. For the zooplankton, about 27 species were observed and classified into 8 functional groups. The study revealed that the bottom-up effects of physical-chemical variables on some phytoplankton functional groups was stronger than the top-down effects of zooplankton. Water temperature (WT), total phosphorus (TP), total nitrogen (TN), conductivity (Cond), water transparency (SD), and dissolved oxygen (DO) significant influence the biomass of the phytoplankton functional groups. The biomass of phytoplankton functional groups was influenced positively by nutrient availability likely because nutrients influence the growth and reproduction of phytoplankton in freshwater. WT and DO had a positive influence on biomass of phytoplankton functional groups. Conversely, phytoplankton biomass revealed a decreasing trend when SD and Cond significantly increased. This study showed that zooplankton functional groups were positively correlated with phytoplankton biomass implying that the top-down control of phytoplankton by the zooplankton in the lake is not strong enough to produce a negative effect. It is evident that the zooplankton functional groups in Lake Hulun are controlled more by bottom-up force than top-down.

Bagasse is an agricultural by-product derived from the sugarcane milling process. It is a dry and fibrous residue left after the extraction of sugar juice from sugarcane. Over 2 million metric tons of bagasse is generated each year in South Florida, and need exists to find environmentally sustainable, yet economically viable use for it. Application of bagasse as a potential soil amendment on mineral soils to grow sugarcane seems like a good option to utilize the product. This factsheet explores the feasibilty of using bagasse as a organic soil amendment to grow sugarcane on mineral soils in South Florida.

Particle size is one factor affecting phosphorus (P) dynamics in soils and sediments. This study investigated how flow facilitated by hydraulic pumps and aquatic vegetation species water lettuce (Pistia stratiotes) and water hyacinth (Eichhornia crassipes) affected particle size and P-dynamics in organic sediments in agricultural drainage ditches. Sediments with finer particle size (>0.002 mm) were hypothesized to contain greater total P (TP) and less labile P than sediments with coarser particle size. Particle size was determined using a LS 13 320 Laser Diffraction Particle Size Analyzer. Sediments were tested for pH, TP, and organic matter. Fractions of P were determined using a sequential fractionation experiment and 31P Nuclear Magnetic Resonance (NMR) Spectroscopy. Larger average particle size and lower average total P concentrations were found in the inflows of the field ditches compared to the outflows. Presence of flow and aquatic vegetation did not have a significant impact on particle size, TP, or labile P fractions. Median (p = 0.10) particle size was not significantly correlated to TP. Overall, there was an average trend of coarser particle size and lower P concentrations in the inflow compared to the outflow. The presence of inorganic limerock could have affected results due to increased P adsorption capacity and larger average particle size compared to the organic fraction of the sediment.

The rice water weevil, Lissorhoptrus oryzophilus Kuschel, is an important pest of rice (Oryza sativa L.) grown in Florida. Reports on the effect of flood depth on rice water weevil populations have been inconsistent. Our objective was to determine if flood depth has any significant effect on rice water weevil populations and other arthropods in rice grown in Florida. Sampling was conducted using adult foliar damage scars, core samples for larvae, and sweep nets for arthropods above the water. Results showed that shallow flooding reduced rice water weevil populations in Florida. Sweep net data showed that flood depth had little, if any, effect on populations of damselflies (Odonata), leafhoppers (Cicadellidae), spiders (Arachnida), or stink bugs (Oebalus spp.).

The purpose of this study is to describe the methods used to capture flow-weighted water and suspended particulates from farm canals during drainage discharge events. Farm canals can be enriched by nutrients such as phosphorus (P) that are susceptible to transport. Phosphorus in the form of suspended particulates can significantly contribute to the overall P loads in drainage water. A settling tank experiment was conducted to capture suspended particulates during discrete drainage events. Farm canal discharge water was collected in a series of two 200 L settling tanks over the entire duration of the drainage event, so as to represent a composite subsample of the water being discharged. Imhoff settling cones are ultimately used to settle out the suspended particulates. This is achieved by siphoning water from the settling tanks via the cones. The particulates are then collected for physico-chemical analyses.

This article highlights the importance of raising soil organic matter in sandy and calcareous soils as it relates to increasing the water holding capacity of the soil. Farming in Florida on sandy soils has numerous limiting factors; one of which is it's low water holding capacity. By raising the soil organic matter content by just 1% can have a significant increase in soil water holding capacity. This would mean that soil would be able to hold more water for long durations. The prospect of increasiong water holding capacity in soils is great for agricultural productivity, and can have a significant impact on water conservation and usage.

The addition of organic amendments and cover cropping on sandy soils are regenerative farming practices that can potentially enhance soil health. South Florida mineral soils present low soil quality due to their sandy texture and low organic matter (OM) content. Few studies have focused on evaluating the effects of farm-based management regenerative practices in this region. The objective of this study was to evaluate changes in soil properties associated with two regenerative farming practices - horse bedding application in combination with cover cropping (cowpea, Vigna unguiculata), compared to the practice of cover cropping only for two years. The soil quality indicators that were tested included soil pH, bulk density, water holding capacity, cation exchange capacity, OM, active carbon, soil protein and major nutrients (N, P, K). Results indicated no significant changes in soil pH, but a significant reduction in soil bulk density and a significant increase in maximum water holding capacity for both practices. Cation exchange capacity and the amounts of active carbon increased significantly after 1.5-year of the farming practices. Horse bedding application with cover cropping showed a significant 4% increase in OM during a short period. A significant increase in plant-available P was also observed under these two practices. Based on this study, horse bedding application as an organic amendment in conjunction with cover cropping provides an enhanced soil health effect compared to just cover cropping. As local growers explore farming option to improve soil health particularly during the fallow period using regenerative farming practices on sandy soils, these results will assist in their decision making.

Wetlands are often referred to as "nature's kidneys" because of their ability to remove pollutants from water via storage in the soil and vegetation, as well as through losses to the atmosphere. This 7-page fact sheet written by Jay Capasso, Lisa Krimsky, and Jehangir Bhadha and published by the UF/IFAS School of Forest Resources and Conservation provides a general overview of the function and structure of large-scale treatment wetlands and the services they provide. http://edis.ifas.ufl.edu/fr419

This 5-page document pertains to the UF/IFAS Extension programs related to rice production in the EAA and focuses on the steps that comprise postharvest processing of rice (drying, tempering, milling, and storage). It aims to highlight the physiology of the rice kernel and define some of the common terms used in the rice industry, elaborate on the steps in postharvest processing, and provide a brief overview of rice products and their market potential. Written by Jehangir H. Bhadha, Sangeeta Mukhopadhyay, Charlene Andrews, and Matthew VanWeelden, and published by the UF/IFAS Agronomy Department, September 2019. http://edis.ifas.ufl.edu/ag438

The Everglades Agricultural Area (EAA), USA, comprises nearly 280,000 ha of organic soil farmlands that are drained by a network of farm canals. During the wet summer season, the water-table in the farmlands is maintained by moving water from farm canals via low-fit, high-volume drainage pumps. The drainage pumping creates a hydraulic pressure gradient, which has the potential to deliver particulate and dissolved substrates from surrounding farmlands into farm canals. This study investigated the role that seasonal drainage plays on the fate and transport of farm canal water including nutrients and metals, plants, and sediments. Intact sediment cores were collected from eight farm canals during the months of November and June, sectioned into two depth intervals (0–2.5 and 2.5–5 cm), and tested for organic matter (OM), phosphorus (P), iron (Fe), and aluminum (Al). In addition, water from the canal (core-water) was also collected and tested for total P, total dissolved P, soluble reactive P, particulate P, dissolved organic carbon, and calcium (Ca). Oxalate extractable Fe, Al, and P were used to estimate sediment P storage capacity. In order to evaluate the seasonal variability in aquatic vegetation coverage in the farm canals, spatial assessment of coverage was conducted every 2 months over a 2-year period. Significant increases in Fe and Al concentrations were observed in the sediment in November compared with June, possibly derived from surrounding soils. The source of OM to the sediments was directly associated with aquatic plants, following a seasonal trend. Total P and Ca were significantly higher in the water during June compared with November. The seasonal trends in sediment and core-water concentrations can be explained by groundwater inputs, surface runoff, and plant coverage within farm canals. High concentrations of Fe and Al in the sediments did not reflect a high P storage capacity, due to the presence of high OM content and seasonal fluctuations in redox potential. The discharge of groundwater from surrounding farmlands is seasonal and has the potential to deliver nutrients, OM, and metals into adjacent farm canals. During summer, primary productivity is at its peak, and this has a direct effect on the percent aquatic plant coverage, nutrient cycling, and P storage capacity within the farm canals. Within the EAA farm canals, the presence of Ca-carbonate may have a greater influence on P storage capacity of the sediments than Fe and Al.

Purpose Excess nutrients such as phosphorus (P) transported from the Everglades Agricultural Area (EAA) in South Florida, USA, to downstream water bodies have been identified as contributing to trophic imbalances within the Florida Everglades. Decades of farming drainage from the EAA has led to accumulation of sediments in regional canals which may be transported to downstream ecosystems and act as potential internal source of P.

Equilibrium phosphorus concentration (EPC) is the aqueous phosphorus (P) concentration at which no net adsorption or desorption occurs when a soil is in contact with water; and are typically determined experimentally by plotting the measured amount of sorption versus initial concentration of P. In this study we evaluated the effect experimental parameters such as equilibration time, soil:solution ratio (SSR), and solution electrolyte may have on EPC values for two distinctly different soil types, (i) organic muck soil, and (ii) loamy mineral soil. Results indicate that there is a significant difference in emerging EPC values with changing equilibrium time, SSR, and electrolyte. For the muck soil, we observed up to 97% decrease in EPC while increasing equilibration time from 1 to 8 h using 1:10 SSR. For the same soil the most profound effect of SSR was observed for 1 h equilibration where EPC value decreased from 0.19 mg L− 1 using 1:2 SSR to 0.03 mg L− 1 using 1:20 SSR, corresponding to an 84% change. The EPC of the loamy soil decreased by 94% while increasing equilibration time from 24 to 72 h using 1:20 SSR, whereas the same soil change in SSR was highly variable. Overall there was a 38% increase in EPC values using 0.01 M CaCl2 compared to KCl as the solution electrolyte in the experiment. These results indicate that experimental conditions can significantly affect EPC values (besides other factors) and therefore need to be standardized especially when used as a tool to assess P loading in natural systems.

Two aluminum water treatment residuals (Al-WTRs) from water treatment plants in Manatee County, FL and Punta Gorda, FL were evaluated as potential permeable reactive barrier (PRB) media to reduce groundwater phosphorus (P) losses. Short-term (24h) P sorption kinetics and long-term P sorption capacity were determined using batch equilibration studies. Phosphorus desorption was characterized following P loadings of 10, 20, 30, 40 and70 g kg(-1). Sorption and desorption studies were conducted on the2.0mm material and three size fractions within the2.0mm material. The effect of dissolved organic carbon (DOC) on P retention was determined by reacting Al-WTRs with P-spiked groundwater samples of varying initial DOC concentrations. Phosphorus sorption kinetics were rapid for all size fractions of both Al-WTRs (98% P sorption effectiveness at shaking times ≥2 h). The effect of DOC was minimal at150 mg DOCL(-1), but modest reductions (22%) in P sorption effectiveness occurred at 587 mg DOC L(-1). The P sorption capacities of the Manatee and Punta Gorda Al-WTRs (2.0mm) are ∼44 g kg(-1) and75 g kg(-1), respectively, and the lifespan of an Al-WTR PRB is likely many decades. Desorption was minimal (2% of the P sorbed) for cumulative P loadings40 g kg(-l), but increased (9% of the P sorbed) at cumulative P loads70 g kg(-1). The2.0mm Manatee and Punta Gorda Al-WTRs are regarded as ideal PRB media for P remediation.

Internal loading is a critical component of the phosphorus (P) budget of aquatic systems that can control trophic conditions. While diffusion across the soil–water interface is generally considered the dominant process controlling P load to the water column, advection due to water table fluctuations can also be significant. Our objective was to evaluate the role of diffusive and advective fluxes in relation to the total P (TP) loads entering and exiting an impacted wetland in the Lake Okeechobee drainage basin. The average diffusive flux of TP was 0.32 ± 0.14 mg m−2 day−1 and occurred for 240 days out of 314, while advective flux was 1.31 ± 4.03 mg m−2 day−1 and occurred for only 57 days. Phosphorus load to the wetland via internal modes was estimated to be 2.3 and 4.0 g day−1 from diffusion and advection respectively, accounting for 18% of the total P input, while overland flow (51%) was the major input pathway to the wetland. Ditch flow and groundwater outflow accounted for 49% (18.0 g day−1) and 14% (5.0 g day−1) of the total P output, respectively. This study shows the importance of advective flux in addition to diffusive flux and that the former should not be neglected when estimating internal P load of transiently flooded isolated wetlands. The monthly P budget-based retention and release patterns were consistent with previous findings, showing that intermittent flooding and drying cycling significantly reduces the P retention capacity of a wetland.