Ammonia Loss Mitigation from Urea Amended Sandy and Calcareous Soils Using Zeolite

Introduction

Nitrogen is an essential element of plants amino acids which are the building blocks of plant proteins, the important components in the growth and development of vital plant cells and tissues such as membranes and chlorophyll (Xia et al., 2011). The ammonium and urea-based fertilizers are susceptible to nitrogen loss as an ammonia (NH₃) gas, especially when they are left on the soil surface. Ammonia volatilization is one of the main factors that are responsible for the low efficiency of nitrogen fertilizer and the significant economic loss (Alberto, 2014).  Urea is considered the cheapest nitrogen fertilizer and widely used in plant nutrition. Urea produces excessive amounts of ammonium carbonate by the biological hydrolysis in soil within 4 days after application. The presence of (NH₄)₂CO₃ raises the soil pH to more than 9.0 which favors the production of NH₃ and its loss into the atmosphere (Gameh, 1991).  The proportion of nitrogen lost from nitrogen fertilizers due to NH₃ volatilization may reach to 50%, depending on fertilizer type, environmental conditions (temperature, wind speed, and rain), and soil properties (calcium content, cation exchange capacity and acidity) (Sommer et al., 2004).

Zeolite minerals are crystalline hydrated aluminosilicates (tectosilicates) of alkali or alkaline earth cations, structured in three dimensional rigid crystalline network and formed by the silica and alumina tetrahedral which come together to compose a system of canals, cavities and pores (Ming and Mumpton,1989). Kaduk and Faber (1995) characterized the pore structure as cages of approximately 1.2 nm in diameter, which are interlinked through channels of about 0.8 nm in diameter and composed of rings of 12 linked tetrahedra. The honeycomb micro-porous structure of zeolite is generally very open, containing pores, long wide channels and cavities, which are filled with cations and water molecules (Karapinar, 2009). Natural zeolite is highly selective for NH⁺₄ and K⁺ relative to Na⁺ or divalent cations such as Ca⁺² and Mg⁺² due to the negative charge location and density in the structure and the dimension of interior channels (0.40 – 0.72 nm diameter) (Ming and Boettinger, 2001). It is clear that the zeolite can retain ammonium ions which are produced during urea hydrolysis and release these ions timely to minimize the rate of converting ammonium to NH₃ (Palanivell et al., 2015). He et al. (2002) indicated that the application of zeolite with nitrogen fertilizer to fine sandy soil significantly reduced NH₃ volatilization compared to the fertilized soil without zeolite addition because of its high cation exchange capacity (CEC) and great affinity for NH₄. In a study, mixing zeolite with dairy slurry reduced ammonia volatilization (Lefcourt and Meisinger, 2001), Moreover, Ahmed et al. (2006 a,b) indicated that zeolite mixed with triple superphosphate and humic acids controlled the ammonia loss from urea in non-waterlogged soils. Also in waterlogged soils, mixing zeolite with peat water decreased ammonia loss from urea and ensured N, P, K uptake and their use efficiency and at the same time causing soil NH₄, K, Ca, Mg, P, and NO₃ ions to be available for plant use (Omar et al., 2010; Latifah et al., 2011). Sandy soil amended with clinoptilolite zeolite (CZ) showed lower NO⁻₃ and NH⁺₄ concentrations in the leachate and to increase the moisture retention in the soil due to the increased soil surface area and CEC (Huang and Petrovic, 1994). In addition, application of (NH₄)₂SO₄ with clinoptilolite to sandy soils was found to minimize N leaching and increase N utilization by crops compared to adding (NH₄)₂SO₄ alone (Perrin et al., 1998).This study aims to evaluate the effect of zeolite application on the NH₃ volatilization loss from sandy and calcareous soils fertilized with urea.

Materials and Methods

Soil sampling

Two soil samples were used in this study. The first sample was sandy soil which collected from uncultivated area (26̊.27ˋ.38.1ˋˋ N and 31̊.39ˋ.50.6ˋˋ E) near El-Kawamel farm, Sohag University, Sohag, Egypt (Table 1). The second soil sample was calcareous soil which collected from the cultivated area (26̊ 35ˋ 27.6ˋˋ N and 31̊ 48ˋ11ˋˋ E) in El-Kawsar farm, Sohag University, Sohag , Egypt  (Table 1). The soil samples were air-dried, passed through 2 mm sieve, mixed thoroughly and kept for this study. The naturally occurring zeolite (clinoptilolite) mineral powder used in this study was obtained from Alex-Zeolite Company, Giza, Egypt (Table 1).

Soil and zeolite analysis

The particle-size distribution of the soil samples was determined using the pipette method (Richards, 1954).The pH of the soil samples and zeolite was measured using a pH meter with a glass electrode (pH 211,Microprocessor pH meter, HANNA Instruments) in a 1:2.5 water suspension (Jackson, 1973). The electrical conductivity of the soil samples was estimated in the soil saturated paste extract and in 1:5 water extract for zeolite using an electrical conductivity meter (Orion model 150) according to Hesse (1998) as well as the soluble cations and anions in these extracts were determined according to Jackson, 1973. The cation exchange capacity (CEC) of soil and zeolite samples was determined using 1 M ammonium acetate at pH 7.0 (Chapman and Pratt, 1961). The calcium carbonate (CaCO₃) was estimated using a volumetric calcium carbonate calcimeter (Jackson, 1973).The total N content of the soil samples was determined by micro-kjeldahl method (Jackson, 1973). The specific surface area of zeolite (S_Bet) was measured using the N₂ adsorption/desorption analysis by micromeritics (ASAB 2000, USA), in the Department of Chemistry, Faculty of Science, Sohag University. The X-ray diffraction (XRD) analysis of zeolite powder was carried out to determine its mineral composition using a Philips X-ray diffraction equipment model PW/1710, Department of Physics, Faculty of Science, Assiut University (Table 2).

Table (1). Some selected properties of the two soils and zeolite mineral

Table (2).  Philips X-ray diffraction analysis of Zeolite sample

The laboratory experiment

A laboratory incubation experiment was carried out in the soil and water Dep., Faculty of Agriculture, Sohag University to study the effect of four levels of zeolite as a soil conditioner on NH₃ loss from urea amended sandy and calcareous soils under room temperature using the system described by Gameh (1987) consisted of an air compressor which pumped the air to pass through distilled water container to produce filtered and humidified air which was distributed through a manifold into soil chambers connected to the system. The soil chambers were glass bottles of 400 cm³ in volume, 6.5 cm in diameter and 14 cm in height. The outgoing air was immersed in 25 ml of 2% boric acid mixed with bromo-cresol green and methyl red indicators which were placed in Bochner flasks to capture the NH₃ gas. The flasks were periodically replaced every 24 hours and titrated using 0.01 N H₂SO₄ for 29 days of incubation.  Four hundred grams of air dried sandy (S) or calcareous (C) soil samples were placed in each glass bottle. Zeolite powder was added to the soil samples at four levels (0, 5, 10 and 20 g/bottel). These levels were equivalent 0, 12.5, 25 and 50 g Kg^-1 soil (0, Z1, Z2 and Z3, respectively) which mixed thoroughly with the soil samples. The soil sample in each bottle was moistened to the field capacity level, and then urea fertilizer (46.5 % N) was added to the soil surface at two levels of 0.1 g (U1) and 0.2 g (U2) per bottle. These respective urea levels were equal to 250 and 500 kg urea fed^-1 (w/w) then, the bottles were immediately closed, and connected to the system. All treatments were arranged in a completely randomized design with three replications (Table 3). The amounts of evolved NH₃ were calculated and daily recorded and the cumulative loss was estimated as a percentage of the applied urea-N. The nitrogen (N) recovery was plotted as a function of the time and fitted through an exponential decay model according to Cohen et al. (2010):

[N]_t = [N]₀ e^-kt

Where:

[N]₀  , [N]_t = N amount (mg) at time 0 and t  days, respectively. 

K = constant, i.e. depletion rate of   N. 

Table (3). The treatments of both sandy and calcareous soils

 U1 and U2 = 250 and 500 kg fed^-1 urea.  Z0, Z1, Z2 and Z3 = 0, 12.5, 25 and 50 g zeolite Kg, respectively.

Results and Discussion

• Ammonia loss from the urea amended sandy soil

1. Daily ammonia loss

The daily ammonia (NH₃) loss from the urea treated sandy soil that was recorded during the incubation time was greater at the high urea level (U2) than that of the low one (U1). However, it decreased with increasing the zeolite applied level (Figures 1 and 2).  The highest daily NH₃ loss for the sandy soil treated with 250 kg fed^-1 of urea (U1) occurred between the 8^th to 11^th days of incubation period. It was 0.81, 0.61 and 0.38% for Z1, Z2 and Z3, respectively, compared to 2.59% for the control (Z0) (Figure 1). However, for the soil amended with 500 kg urea fed^-1 level (U2), the maximum daily NH₃-N loss (%)  was between the 8^th to 10^th day of incubation period (Figure 2) and recorded 1.14, 0.63 and 0.51% for Z1, Z2 and Z3, respectively, compared to 2.74% for the control (Z0) (Figure 2). Then, the daily NH₃ loss decreased gradually with the incubation time.

1. Cumulative ammonia loss

The cumulative volatilized NH₃ from the sandy soil fertilized with urea and amended with different zeolite levels at the end of incubation period is present in Table 4. For the sandy soil amended with urea at a level of 250 kg urea (U1), the application of zeolite significantly reduced the total NH₃ loss from 24.79% in the control treatment (Z0) to 10.18, 5.80 and 4.08% of the total applied urea-N for Z1, Z2 and Z3 respectively at the end of incubation period (29 days) (Table 5). Moreover, for the soil fertilized with urea at 500 kg fed^-1 level (U2), zeolite applications exhibited a reduction in the total NH₃ loss from 27.35% for the control treatment (Z0) to 11.67, 7.75 and 6.05% of the total applied urea-N for Z1, Z2 and Z3 respectively (Table 5).

Figure (1).  Daily NH₃ loss (%) from the sandy soil treated with 250 kg fed^-1 of urea (U1) and amended with Z0, Z1, Z2 and Z3 levels of zeolite

Figure (2).  Daily NH₃ loss (%) from the sandy soil treated with 500 kg fed^-1 urea (U2) and amended with Z0, Z1, Z2 and Z3 levels of zeolite

Table (4). Effect of zeolite levels (Z0, Z1, Z2 and Z3) on the cumulative ammonia loss (%) from urea fertilizer levels (U1 and U2)

 amended sandy soil

U1 and U2 = 250 and 500 kg urea fed^-1  Z0, Z1, Z2 and Z3 = 0, 12.5, 25 and 50 g kg^-1 soil, respectively.

Table (5). Effect of zeolite levels (Z0, Z1, Z2 and Z3) on total volatilized NH₃ (%) from the sandy and calcareous soils fertilized with 250 (U1)   and 500 kg fed^-1 (U2) after 29 days of incubation.

Z0, Z1, Z2, Z3 = 0, 1.25, 2.5 and 5.0 % zeolite.

Different letters indicate statistically significant differences between variables according to their least significant difference (LSD) at 0.05 probability level.

2-Ammonia loss from urea amended calcareous soil

Daily and cumulative NH₃-N losses (%) of the applied urea-N to the calcareous soil during the incubation period (29 days) are present in Figures 3, 4 and Table 6.

1. Daily ammonia loss

The highest daily values of NH₃ loss from urea treated calcareous soil were recorded between the 3^th and 8^th day of incubation (Figures 3 and 4). The highest daily NH₃ loss from U1 amended calcareous soil was 3.46, 2.12 and 1.38 % for Z1, Z2 and Z3, respectively, compared to 10.27 % for the control (Z0) (Figure 3). In addition, in the U2 treated calcareous soil, the respective daily NH₃ loss showed maximum values of 7.22, 2.40 and 1.76% for Z1, Z2 and Z3, respectively, compared to 11.30% for Z0 treatment (Figure 4). After reaching the maximum loss, the daily volatilized ammonia (%) gradually decreased until the end of incubation period.

1. Cumulative ammonia loss

The cumulative ammonia loss (%) from urea amended calcareous soil which was treated with zeolite (Z0, Z1, Z2 and Z3) levels is present in Table 6. For the lower urea level (U1), the addition of zeolite significantly minimized the total NH₃ loss (%) in the calcareous soil at the end of experiment from 61.73% for the control (Z0) to 33.04, 21.83 and 12.13% of the added urea-N for Z1, Z2 and Z3, respectively (Table 5). However, for the higher urea level (U2), zeolite showed a significant effect in reducing the total NH₃ loss from 72.45% for the control (Z0) to 45.67, 26.33 and 19.16% of the total applied urea-N for Z1, Z2 and Z3, respectively (Table 5).

Figure (3). The daily NH₃ loss (%) from the calcareous soil fertilized with 250 kg urea fed^-1 (U1) and amended with Z0, Z1, Z2 and Z3 levels of zeolite

Figure (4). The daily NH₃ loss (%) from the calcareous soil treated with 500 kg urea fed^-1 (U2) and amended with Z0, Z1, Z2 and Z3 levels of zeolite

   Table (6). Zeolite effect on the cumulative ammonia loss (%) from urea fertilized calcareous soil            

U1 and U2 = 250 and 500 kg urea fed^-1  Z0, Z1, Z2 and Z3 = 0, 12.5, 25 and 50 g kg^-1 soil, respectively.              

It is noticeable that nitrogen volatilization loss from the calcareous soil is higher than that from the sandy soil. It may be attributed to the higher pH value and the higher CaCO₃ content of the calcareous soil. Calcium carbonate (CaCO₃) increases (NH₄)₂CO₃ production from urea that hydrolyzed into NH₃ gas, CO₂ gas and H₂O (Gameh, 1991; Jones et al., 2013). The results also indicate that increasing the applied urea-N level results in more NH₃ loss in both soils leading to a reduction in the nitrogen use efficiency as the amount of applied urea fertilizer increases (Ibrahim, 1999; El-Mamlouk, 2006 ; Rochette et al., 2013). It is obvious that the NH₃ loss from the soil decreases as the applied level of zeolite increases. The effective role of zeolite in reducing the volatilization loss of NH₃ may be due to the presence of clinoptilolite which is the most dominant mineral in the used zeolite ore. Clinoptilolite zeolite is a mineral with a unique structure which allows trapping or releasing various cations due to its high cation exchange capacity (Kamarudin et al., 2003). It can be used to control N loss from urea because of its small molecular size of the open-ring structure which physically protects NH₄⁺ ions against microbial nitrification (Ferguson and Pepper, 1987). The slow retention and liberation ability of NH⁺₄ ions that have been incorporated in the channels forming crystalline structure is generally attributed to zeolites, and particularly clinoptilolite (Allen et al., 1996; Kithome et al., 1998). Adsorption of ammonium by clinoptilolite zeolite reduces the NH₃ volatilization loss, maximizes N use efficiency and water use efficiencies and may decrease the excessive and unbalanced use of N fertilizers in agriculture (McGilloway et al., 2003).

3-Kinetics of NH₃ loss from urea amended sandy and calcareous soils

The average values of N recovery (mg) from urea fertilizer applied to the sandy and calcareous soils as a function of the incubation time are present in Figures 5,6 ,7 and 8 respectively. The higher ammonia volatilization loss from the calcareous soil resulted in higher nitrogen depletion rate (k) compared to those of the sandy soil. Amending the sandy soil with zeolite reduced  the depletion rate (k value) from  0.010 for the control (Z0) to 0.004, 0.002 and  0.001 in Z1, Z2 and Z3, respectively for the U1 (250 kg urea fed^-1) treatment, and from 0.012  for the control (Z0) to 0.005 ,  0.003 and 0.002 in Z1, Z2 and Z3, respectively, for U2 (500 kg urea fed^-1) treatment (Table 7). However, for the zeolite amended calcareous soil, the nitrogen depletion rate (k) reduced from 0.027 for the control (Z0) to 0.013, 0.08 and 0.004 in Z1, Z2 and Z3, respectively for the U1 (250 kg urea fed^-1) treatment, and from 0.041 in the control (Z0) to 0.019, 0.011 and 0.008 in Z1, Z2 and Z3, respectively for that fertilized at the U2 (500 kg urea fed^-1) treatment (Table 7). Similar results were showed by Ibrahim (1999) who recorded an increase in the depletion rate (k) of ammonium as the zeolite level increased and a decrease in that rate as the fertilization level increased for sandy soil.

Figure (5).  Nitrogen recovery (average values) from the sandy soil treated with 250 kg urea fed^-1 (U1) after zeolite additions as a function of the incubation time

Figure (6). Nitrogen recovery (average values) from the sandy soil treated with 500 kg urea fed^-1 (U2) after zeolite additions as a function of the incubation time

Figure (7).  Nitrogen recovery (average values) from the calcareous soil amended with 250 kg fed^-1 urea (U1) after zeolite additions as a function of the incubation time

Figure (8). Nitrogen recovery (average values) from the calcareous soil treated with 500 kg urea fed^-1 (U2) after zeolite additions as a function of the incubation time

Table (7). Nitrogen reduction rate constant (k) and coefficient of determination (R²) of the sandy and calcareous soils fertilized with 250   (U1), 500 kg urea fed^-1 (U2) and amended with zeolite (Z0, Z1, Z2 and Z3)

           Z0, Z1, Z2 and Z3 = 0, 12.5, 25 and 50 g zeolite kg^-1 soil respectively.              

Conclusion

The present study indicates that using zeolites as soil amendment in the sandy or calcareous soils reduces the volatilization loss of ammonia as well as increases the nitrogen recovery efficiency as a result of remaining the N nutrient in the form of NH⁺₄ or NO^-₃ in the soil.