D. J. Banks

Nitrogen mineralization and transformation from composts and biosolids during field incubation in a sandy soil.

Field evaluation of nutrient release from composts is important to estimate nutrient contribution to crops, potential leaching of nutrients, and, ultimately, to determine optimum application rates, timing, and placement of composts. Field incubation and laboratory analyses were conducted to evaluate

AMMONIA VOLATILIZATION FROM DIFFERENT FERTILIZER SOURCES AND EFFECTS OF TEMPERATURE AND SOIL pH1

Improved understanding of nitrogen sources, environmental factors, and nitrification effects on NH 3 volatilization is needed for optimal management of nitrogen in crop production systems. In the laboratory, a sponge-trapping and KCl-extraction method was modified for measuring NH 3 volatilization from different N sources as affected by temperature and soil pH. The kinetics of NH 3 volatilization from four N sources surface applied to an Alfisol (a Riviera fine sand, pH 7.9) followed an initial rapid reaction, and then a slow reaction, which was adequately described by a Langmuir kinetic model. The potential maximum NH 3 volatilization (q m ) under the experimental conditions, as predicted by the Langmuir equation, decreased in the order: NH 4 HCO 3 (23.2% of applied NH 4 -N) > (NH 4 ) 2 SO 4 (21.7%) > CO(NH 2 ) 2 (21.4%) > NH 4 NO 3 (17.6%). With an increase in NH 4 -N application rate, NH 3 volatilization increased significantly for (NH 4 ) 2 SO 4 , CO(NH 2 ) 2 , and NH 4 HCO 3 but decreased for NH 4 NO 3 . Ammonia volatilization was minimal at the initial soil pH of 3.5 and increased rapidly with increasing pH up to 8.5. The potential maximum NH 3 volatilization increased by 2- and 3-fold, respectively, with an increase in the incubation temperature from 5 to 25 °C, and from 25 to 45 °C, respectively. The greatly enhanced NH 3 volatilization at 45 °C, compared with that at 25 °C, was related to the inhibition of nitrification at the high temperature, which increased the availability of NH 4 for NH 3 volatilization over a prolonged period of time.

Clinoptilolite zeolite and cellulose amendments to reduce ammonia volatilization in a calcareous sandy soil

Leaching of nitrate (NO3−) below the root zone and gaseous losses of nitrogen (N) such as ammonia (NH3) volatilization, are major mechanisms of N loss from agricultural soils. New techniques to minimize such losses are needed to maximize N uptake efficiency and minimize production costs and the risk of potential N contamination of ground and surface waters. The effects of cellulose (C), clinoptilolite zeolite (CZ), or a combination of both (C+CZ) on NH3 volatilization and N transformation in a calcareous Riviera fine sand (loamy, siliceous, hyperthermic, Arenic Glossaqualf) from a citrus grove were investigated in a laboratory incubation study. Ammonia volatilization from NH4NO3 (AN), (NH4)2SO4(AS), and urea (U) applied at 200 mg N kg−1 soil decreased by 2.5-, 2.1- and 0.9-fold, respectively, with cellulose application at 15 g kg−1 and by 4.4-, 2.9- and 3.0-fold, respectively, with CZ application at 15 g kg−1 as compared with that from the respective sources without the amendments. Application of cellulose plus CZ (each at 15 g kg−1) was the most effective in decreasing NH3 volatilization. Application of cellulose increased the microbial biomass, which was responsible for immobilization of N, and thus decreased volatilization loss of NH3–N. The effect of CZ, on the other hand, may be due to increased retention of NH4 in the ion-exchange sites. The positive effect of interaction between cellulose and CZ amendment on microbial biomass was probably due to improved nutrient retention and availability to microorganisms in the soil. Thus, the amendments provide favorable conditions for microbial growth. These results indicate that soil amendment of CZ or CZ plus organic materials such as cellulose has great potential in reducing fertilizer N loss in sandy soils.

Nitrogen Transformation and Ammonia Volatilization From Biosolids and Compost Applied to Calcareous Soil

One benefit of the use of composts and biosolids in agriculture is their nitrogen supplying capacity. Redeposition of ammonia volatilized from surface applied composts and biosolids may contaminate surface water and sandy soils. Laboratory incubation studies were conducted to quantify NH3 volatilization from a West Palm cocompost (WPCC) and biosolids (BSD) either surface applied or soil incorporated and to determine the relationship between NH3 volatilization and nitrogen mineralization. Such information is required to formulate guidelines for field application of composts or biosolids. Ammonia volatilization from the WPCC- or BSD amended soil was closely related to nitrogen mineralization and application method. More NH3 was volatilized from the BSD than the WPCC, which likely resulted from higher total N concentration and lower C/N ratio of the BSD. Nitrogen volatilization losses were greater with surface application than with soil incorporation. The amounts of NH3-N volatilized during an 180-d incubation period accounted for 18% and 23% of the total mineralized N for the surface applied BSD and WPCC, respectively. Soil incorporation increased nitrogen mineralization by more than 60% in the BSD and by 8-fold in the WPCC, but reduced NH3 volatilization by 5- and 150-fold, respectively for the BSD and WPCC.

Nutrient Availability and Changes in Microbial Biomass Of Organic Amendments During Field Incubation

Field evaluation of release and availability of nutrients and potentially toxic elements from composts is necessary to estimate their nutrient contribution to crops, potential effect on soil and environmental quality. A biosolids (BSD), a yard waste (YW), and a West Palm Beach cocompost (WPCC) were incubated under field conditions in a citrus grove on an Oldsmar fine sandy soil (sandy, siliceous, hyperthermic Alfic Arenic Haplaquods). The incubation columns and the soil underneath each column were sampled on 0, 240, and 360 days after incubation and analyzed for KCl extractable NH4-N and NO3-N, 0.5 M NaHCO3 extractable P, and Mehlich 3 extractable K, Fe, Mn, Zn, Cu, and microbial biomass. The total concentration and extractable proportion of each element greatly varied among the three organic amendments. Approximately 34-73% of K, 1-14% of Fe, 7-68% of Zn, 7-47% of Mn, and 2-34% of Cu in the three organic amendments were extractable by the Mehlich 3 reagent at the beginning of incubation. Incubation of these amendments under field conditions for a period of 1 yr increased the availability of N, P, K, and several micronutrients including Fe, Cu, Zn, and Mn. Microbial biomass-C and -P were markedly increased during the field incubation. However, the BSD, containing high total C and other nutrients, produced less microbial biomass-C than the two composts. The rapid increase in concentrations of available metals including Cu, Zn, and Mn in the BSD during the incubation may have adverse effects on microbial biomass growth and proliferation in this compost. A combination of BSD and YW improved conditions for the microbial biomass growth as evidenced by the increase in microbial biomass C and P of this combination during the course of incubation.

Nutrient leaching potential of mature grapefruit trees in a sandy soil

There has been increasing concern over nutrient loss from agricultural practices that may contribute to the accelerated contamination of groundwater and surface waters. This concern is greater in sandy soils, which have minimal nutrient retention capacity. Both field- and column-leaching studies were conducted to examine the leaching of NO - 3 , PO 3- 4 , and K in a Riviera fine sand (loamy, siliceous, hyperthermic, Arenic Glossaqualf) under grapefruit production that received 0 to 168, 0 to 30, and 0 to 168 kg ha -1 yr -1 of N, P, and K, respectively. The concentrations of NO 3 -N, PO 4 -P, and K were measured in soil solution sampled using suction lysimeters installed above (120 cm) and below (180 cm) the hardpan. Column leaching was conducted using soil collected from 0 to 30, 30 to 60, 60 to 90, 90 to 120, 120 to 150, and 150 to 180 cm of the profile, and the amounts of N, P, and K applied to the leaching column were equivalent to the application rates in the field. The concentrations of NO 3 -N, PO 4 -P, and K in soil solution at both 120- and 180-cm depths increased with increasing fertilizer rates. Fertigation tended to enhance leaching of NO 3 -N, PO 4 -P, and K compared with dry soluble granular application. The concentrations of NO 3 -N and PO 4 -P in soil solution were much higher at the 120 cm depth than at the 180 cm depth, whereas the reverse was true with respect to K solution concentrations. The average concentrations of NO 3 -N in soil solution at both the 120- and 180-cm depths over 3 years were well below 10 mg L -1 , the U.S. Environmental Protection Agency (U.S. EPA) drinking water quality standard, even at the highest rate of fertilizer application. Solution K concentrations at the 180-cm depth were close to or slightly higher than 12 mg L -1 , the maximum level for drinking water set by the European Community. Solution PO 4 -P concentrations at the 120-cm depth (average 0.25 to 0.70 mg L -1 over 3 years for plots receiving various amounts of fertilizer) were much higher than the U.S. EPA criteria for fresh waters (0.025 mg L -1 in lakes and 0.05 mg L -1 in streams) and may constitute a P source for surface waters as soil solution above this depth is likely to seep into water furrows through lateral movement and be discharged into drainage water. A column leaching study demonstrated that the argillic horizon in the Riviera fine sand effectively reduced downward movement of PO 4 -P and K because it had a much greater sorption capacity for phosphate and K, but it had much less effect on the vertical transport of NO 3 -N along the soil profile. The results indicate that best management practices in this sandy soil region should be directed to minimizing the leaching of PO 4 -P and K in addition to NO 3 -N.

Leaching Behavior of Heavy Metals In Biosolids Amended Sandy Soils

Use of biosolids in agriculture to improve crop production and soil quality have created concerns due to content of heavy metals that may affect surface or ground water quality. A column leaching study was conducted to evaluate the leaching potential of copper (Cu), lead (Pb), zinc (Zn), cdmium (Cd), cobalt (Co), chromium (Cr), and nickel (Ni) from two typical agricultural sandy soils in South Florida (Spodosol and Alfisol) with increasing application of pelletized biosolids (called PB) at the rates of 0, 1.25, 5.0, 10.0 g kg−1, respectively together with chemical fertilizer (CF). Elevated PB rate resulted in reduced leaching loss of Cu, Pb, Zn, Cd, Co, Ni from Spodosol, but resulted in increased loss of Pb, Zn, Cd, and Co from Alfisol. Significant reduction in Cu loss occurred in both soils, which can be attributed to the strong binding of Cu with organic matter from the applied PB. Percentage of Cd loss as of total Cd was 13% – 41%, the highest in all the heavy metals, whereas loss of Pb as of total Pb was less than 6.6%, though the concentrations of Pb, Cd, Co, and Ni in leachate were mostly above the limits of U.S. EPA drinking water standards or the national secondary drinking water standards. These results indicate that soil properties, PB application rates, and chemical behavior of elements jointly influence the leachate total loads of heavy metals in sandy soils applied with biosolids. Application of CF together with BP at a rate higher than 10.0 g kg−1 for sandy soils may pose potential threats to water quality due to enhanced leachate loads of Cr and Ni in Spodosol and Pb, Zn, Cd, Co and Ni in Alfisol.

Effects of leaching solution properties and volume on transport of metals and cations from a riviera fine sand

Abstract A column leaching study was conducted using a Riviera fine sand (Loamy, siliceous, hyperthermic, Arenic Glossaqualf), sampled at 30 cm increments to 150 cm depth, from a commercial grapefruit grove to evaluate the effects of leaching solution properties on the leaching of Zn, Cu, Mn, Fe, Ca, and Mg in seven pore volumes of leachate. The concentration of Cu in the leachate was highest in the surface horizon (0–30 cm), indicating its limited transport down the soil profile. The concentration of Zn was significantly greater in the 30–60 cm depth sample than at the other depths. The peak concentrations of Fe and Mn were found in the 60–90 cm depth while those of Ca and Mg were in the 120–150 cm depth. The concentrations of the above metals and cations were significantly correlated with those of Mehlich 3 extractable elements in the soil. The addition of N, P, and K to the leaching solution increased the Zn, Mn, Ca, and Mg concentrations, but decreased Fe and Cu concentrations in the leachate. The concentrations of Ca, Mg, and Mn in the leachate were positively correlated, while those of Cu and Fe were negatively correlated with electrical conductivity of the leachate. The cumulative amounts of metals in the leachate increased with an increase in the pore volume of the leachate. The leaching solution pH was negatively correlated with concentrations of Zn, Mn, Fe, and positively correlated with concentration of Ca in the leachate.

Adsorption and transport of nitrate and bromide in a Spodosol

Spodosols are important soil types throughout much of the citrus belt in the south and east coast regions of Florida. The spodic horizon in these soils may play a role in restricting the transport of contaminants; hence, it could minimize the contamination of groundwater by agrichemicals applied to soils. In this study, adsorption and leaching of nitrate and bromide in soil samples taken from three horizons of a Spodosol (Oldsmar sand; sandy, silicious, hyperthermic Alfic Arenic Haplaquods) were evaluated with batch equilibration and leaching column experiments. Adsorption of nitrate and bromide was negligible by the A (surface soil, 0-20 cm) and E (sand layer, 25-50 cm) horizon samples. The spodic horizon (Bh, 55-70 cm), by comparison, retained a small amount of nitrate and bromide. In a leaching column study, the quantity of nitrate, applied on the surface of the soil column, recovered in 4.5 pore volumes of leachate was lower by 15% when the soil sample from the spodic horizon was used compared with using the surface or the sand horizon samples. A 2-fold increase in rate of application of either nitrate or bromide had a negligible effect on the cumulative leaching of the ions in relation to the quantity applied.