Ammonium and nitrate transport during saturated and unsaturated water flow through sandy soils

Abstract

Citrus production in Florida accounts for ≈ 60% of national production in USA. The sandy soil characteristic (> 95% sand) makes water and nutrient management extremely difficult, raising concerns about environmental sustainability as a result of nutrient inputs in citrus producing regions where sandy soils dominate. Thus, laboratory column and field experiments were conducted to better understand the leaching patterns of NH4 + and NO3 - ions in Florida's sandy soils. The soil columns were first saturated from the bottom with two pore volumes of simulated Florida rain followed by pumping a pulse of fertilizer mixture at a steady Darcy flux of 14 cm h−1. Nitrate and Cl− appeared earlier in the effluent than NH4 + in the A and Bh horizons, due to cation exchange of NH4 + . Essentially identical breakthrough curves (BTCs) for NH4 + and NO3 - were observed in the E‐horizon, due to very low sorption of NH4 + . The convective and dispersive equilibrium (CDE) model simulations were in good agreement with measured breakthrough curves (BTCs) for NH4 + , NO3 - , and Cl−. However, the sorption coefficient (KD) values used in the CDE model to simulate the BTCs for NH4 + were about 10 times less than the batch isotherm KD values. This was attributed to differences in pH, cation composition, and ionic strength between batch (static) and dynamic (leaching) systems. The field experiment showed that under unsaturated flow, improved short‐pulse fertigation systems (drip and microsprinkler) limited NH4 + and NO3 - transport beyond the root zone (top 30 cm), which might have promoted nutrient and water uptake in citrus. The column study revealed that under extreme weather events such as hurricanes or storm surge in Florida, saturated soil conditions can trigger N mobility below the root zone to surficial or groundwater aquifers. In the field experiment, the use of judicious, minimal and split applications and accurate placement of N‐fertilizers reduced leaching of N especially during heavy storms in the summer rainy months of Florida. The field experiment demonstrated that it is possible to manage inorganic N forms for optimal residence time for uptake and minimal leaching concerns.

Modeling Water and Nutrient Movement in Sandy Soils Using HYDRUS‐2D

“…Nitrate and NH 4 were well predicted by the model (Fig. 3; see also Kadyampakeni et al, 2017). Potassium, despite the underpredictions, showed very good correlation at Immokalee (Fig.…”

Biological soil crusts enhance moisture and nutrients in the upper rooting zone of sandy soil agroecosystems

“…Each site was approximately 20 rows wide and 120 m in length. The soil types of the agroecosystems were similar in texture as each is primarily a fine sand with an A horizon (0–10 cm) of weak fine granular structure, and most citrus growing areas of Florida are dominated by soils that are > 90% sand content ( Kadyampakeni et al., ). Soils at SWFREC and On‐Farm are characterized as Florida Flatwoods Spodosols with an accumulation of iron, aluminum, and organic matter in the spodic horizon in the subsoil, and CREC is located on Florida Central Ridge Entisols that mostly lack diagnostic horizons ( Mylavarapu et al., ).…”

Nitrogen Sources and Algae Extract as Candidates for Improving the Growth, Yield and Quality Traits of Broccoli Plants

“…Managing N-inputs is an important factor in broccoli production (Schellenberg et al, 2009;Luna et al, 2018) especially in light textured soils (Abd-Alrahman et al, 2016). In such soils, the traditional mineral N-fertilizers are still in use for plant production; however, the extensive use of these fertilizers is associated with significant losses of N from soil through volatilization or nitrate leaching (Peng et al, 2015;Kadyampakeni et al, 2018). This probably possesses ecological hazards.…”

“…Managing N-inputs is one of the important factors affecting broccoli growth and yield development (Schellenberg et al, 2009;Luna et al, 2018) especially in light textured soils (Abd-Alrahman et al, 2016). Although, the traditional farming is still dependent on mineral Nfertilization for vegetables production because these inorganic forms are easily absorbed and utilized by vegetables (Shams, 2012); however, significant losses might occur in mineral N-forms either through ammonia volatilization or nitrate leaching (Peng et al, 2015;Kadyampakeni et al, 2018). This might contribute effectively in N-pollution of the groundwater (Smith et al, 2016) and consequently raises concerns about environmental sustainability (Kadyampakeni et al, 2018).…”

“…Although, the traditional farming is still dependent on mineral Nfertilization for vegetables production because these inorganic forms are easily absorbed and utilized by vegetables (Shams, 2012); however, significant losses might occur in mineral N-forms either through ammonia volatilization or nitrate leaching (Peng et al, 2015;Kadyampakeni et al, 2018). This might contribute effectively in N-pollution of the groundwater (Smith et al, 2016) and consequently raises concerns about environmental sustainability (Kadyampakeni et al, 2018). Thus, increasing consumer awareness has contributed in establishing food safety issues and environmental concerns (Worthington, 2001) through introducing organic and bioapproaches as substitutes for the traditionally mineral fertilization (Abbas et al, 2011;Farid et al, 2014 and.…”