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Evaluation of nitrification inhibitor 3,4-dimethyl pyrazole phosphate on nitrogen leaching in undisturbed soil columns
Chemosphere 67 (2007) 872–878 www.elsevier.com/locate/chemosphere
Evaluation of nitrification inhibitor 3,4-dimethyl pyrazole phosphate on nitrogen leaching in undisturbed soil columns Qiaogang Yu a, Yingxu Chen a
a,*
, Xuezhu Ye b, Qiuling Zhang a, Zhijian Zhang a, Ping Tian
a
Department of Environmental Engineering, Zhejiang University, Hangzhou 310029, China b Zhejiang Academy of Agricultural Sciences, Hangzhou 310021, China
Received 30 June 2006; received in revised form 5 November 2006; accepted 8 November 2006 Available online 4 January 2007
Abstract The application of nitrogen fertilizers leads to various ecological problems such as nitrate leaching. The use of nitrification inhibitors (NI) as nitrate leaching retardants is a proposal that has been suggested for inclusion in regulations in many countries. In this study, the efficacy of the new NI, 3,4-dimethyl pyrazole phosphate (DMPP), was tested under simulated high-risk leaching situations in two types of undisturbed soil columns. The results showed that the accumulative leaching losses of soil nitrate under treatment of urea with 1.0% DMPP, from columns of silt loam soil and heavy clay soil, were 66.8% and 69.5% lower than those soil columns tested with regular urea application within the 60 days observation, respectively. However, the losses of ammonium leaching were reversely increased 9.7% and 6.7% under the former treatment than the latter one. Application of regular urea with 1.0% DMPP addition can reduce about 59.3%– 63.1% of total losses of inorganic nitrogen via leaching. The application of DMPP to urea had stimulated the inhibition effects of DMPP on the ammonium nitrification process in the soil up to 60 days. It is proposed that the DMPP could be used as an effective NI to control inorganic N leaching losses, minimizing the risk of nitrate pollution in shallow groundwater. Ó 2006 Elsevier Ltd. All rights reserved. Keywords: 3,4-Dimethyl pyrazole phosphate; Nitrification inhibitor; Nitrate leaching; Nitrate pollution; Nitrogen fertilizer
1. Introduction Nitrate leaching from arable land, which causes contamination of groundwater, has become a worldwide environmental concern. In rural plain areas of Beijing, nitrate-N 1 (NO were found 3 -N) concentrations exceeding 10 mg l in above 20% of the investigated groundwater samples in 2000 (Liu et al., 2005). Excessive use of readily available conventional chemical fertilizers to agriculture land is the main source of groundwater contamination (Thomsen et al., 1993; Adams et al., 1994; Chang and Entz, 1996; Fraters et al., 1998). The nitrate concentrations of groundwater under vegetable fields were significantly higher than those under the urban land or paddy fields (Lyle and Rich*
Corresponding author. Tel.: +86 571 86971159; fax: +86 571 86971898. E-mail address: [email protected] (Y. Chen). 0045-6535/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.chemosphere.2006.11.016
ard, 1997; Groeneveld et al., 1998; Insaf et al., 2004). The vegetable fields were considered as the principal source of groundwater nitrate contamination. To reduce nitrate leaching from agriculture land, one of the proposals currently being considered for inclusion in regulations is the use of slow-release fertilizers, especially for using the fertilizer added with new-type nitrification inhibitors (NI) (Chen et al., 2003; Morihiro et al., 2003). However, little information is available on the efficacy of chemical fertilizers applying with additions of NI in order to reduce nitrate leaching to the groundwater in China. In temperate soils, ammonium is strongly adsorbed to cation exchange sites, whilst nitrate is highly mobile within the soil column. NI are compounds that delay oxidation of the ammonium ion (NHþ 4 Þ to nitrate by suppressing the activity of Nitrosomonas spp. bacteria (Hauck, 1980; Irigoyen et al., 2003). NI can, therefore, theoretically reduce nitrate leaching by retaining nitrogen (N) in a form of
Q. Yu et al. / Chemosphere 67 (2007) 872–878
low mobility (e.g. ammonium-N) (Kurtz, 1980; Shen et al., 2003). On the other hand, NI decrease nitrate concentration in soil, and as a result, they also decrease N losses through run off (Fettweis et al., 2001) and denitrification (Bronson et al., 1992; Delgado et al., 1996; Weiske et al., 2001; Zhu et al., 2003). When the N-use efficiency is improved, and N doses and the rate of fertilizing applications are decreased, both economic and environmental benefits are achieved. A lot of chemical material, both natural and synthetic, shows nitrification-inhibiting capabilities (Prasad and Power, 1995). Commercially available N fertilizers incorporate dicyandiamide (DCD) and nitrapyin (Amberger, 1989), and recently, 3,4-dimethyl pyrazole phosphate (DMPP ) has also been used in agriculture crops (Prasad and Power, 1995; Serna et al., 2000). Generally, DCD is just too expensive for large-scale use in agriculture, and its efficiency is comparatively low, even resulting in phytotoxicity problems under certain climate conditions (Zerulla et al., 2001). Moreover, nitrapyin belongs to the group of organic chlorine compounds, and the release of nitrapyin into the environment faces the increasing opposition because it poses certain toxicological problems (Zerulla et al., 2001). On the contrary, DMPP belongs to a chemical group that has been demonstrated to be very efficient in inhibiting the nitrification process in the soil, and was found no toxicological and eco-toxicological side-effect based on extensive standard toxicology and eco-toxicology tests (Zerulla et al., 2001). At present, there are few studies on the effect of DMPP on the reduction of N leaching from vegetable fields. In this study, undisturbed soil columns were used to illustrate the effect of the DMPP on inorganic N loss by simulating leaching condition of vegetable fields. 2. Materials and methods 2.1. Experimental soils Two experimental soils for this study were sampled from the southeast of China. The silt loam soil is collected from Jianggang Town (120.2E, 30.3N), Hangzhou City, Zhejiang Province where the tested soil in the site is classified as the permeable type with a texture of loam silt. Heavy clay soil is collected from the Taihu Basin Region, Jiaxing City (120.7E, 30.8N) where the tested soil is classified as the waterlogged type derived from clay loam deposit. The profile structures of these two soils were also different: the former with a relative uniform and permeable profile while the latter without this layer but with tight impermeable layer of acclimated clay. The basic properties of the experimental soil are shown in Table 1. 2.2. Experimental design The undisturbed soil columns were collected similar to the mortar encasement method of (Preibe and Blackmer, 1989). Briefly, soil was excavated from around a free-standing cylindrical soil column of 16 cm diameter by 50 cm
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Table 1 Some physical and chemical properties of the two soils used in the experiment Parameter
Silt loam soil
Soil depth (cm)
0–15
15–30
30–50
0–15
15–30
30–50
1.88 0.74 20.4 9.88 7.38 29.0 62.7 8.3
1.42 0.66 15.1 9.07 7.12 24.5 66.1 9.4
0.88 0.57 4.8 6.65 7.15 20.7 69.2 10.1
2.43 0.93 23.1 18.25 6.83 46.4 42.1 11.5
1.73 0.79 19.8 18.13 6.96 46.1 44.2 9.7
0.97 0.62 7.7 16.98 7.06 50.3 41.9 7.8
1 a
Total N (g kg ) Total P (g kg1)b Organic C (g kg1)c CEC (cmol kg1)d pHe Clay (%) Silt (%) Sand (%) a b c d e
Heavy clay soil
Bremner (1965). Bray and Kurtz (1945) and Murphy and Rilley (1962). Walkey and Black (1934). Chapman (1965). Soil to water ratio of 1:2.5.
depth. When the soil columns were properly shaped, a polyvinyl chloride (PVC) pipe of 20 cm diameter was placed around the columns, and liquefied petroleum jelly was placed in the space between the soil and the PVC, to prevent edge-flow (Julie et al., 1998). Then the encased soil columns were brought to laboratory for testing. The total pore space and water holding capacity in the silt loam soil column were 41.5% and 30.3%, while those in the heavy clay soil column were 58.6% and 38.4%, respectively. The soil in the 0–3 cm upper part of the column was also from the original field layer 0–5 cm, but was subjected to one of the following treatments with three replicates: (1) no application of fertilizer (control, designated as CK), (2) regular urea application at rate of 200 kg N ha1 only (designated as UA), and (3) application at rate of 200 kg N ha1 added with 1.0% of DMPP (w/w) (designated as DP). Each undisturbed soil column was cultivated with a common regional crop of Cabbage (Brassica campastris L. ssp. pekinesis) which was transplanted with seeding-growth before fertilizer application. The leaching experiment was conducted under the temperature of 18–22 °C and the humidity of 65% in an artificial glasshouse in Zhejiang University. During the period of leaching experiment, 70 ml of distilled water was applied daily from the top of each soil columns representing local daily rainfall, transpiration and evaporation requirements. Soil solution samples were collected from the bottom of soil column at an interval of ten days. 2.3. Sample analysis Water samples were stored in dark at 4 °C in an icebox prior to analyze. The concentrations of NHþ 4 -N and NO -N in leachate were determined by using ion chroma3 tography (IC 20, Dionex, USA), and the Ultraviolet Spectrophotomery (Norman and Stucki, 1981), respectively. The fresh soil samples were extracted by shaking with 2 M KCl at a soil/solution ratio of 1:5 for 30 min, filtering, and then determining the concentration of NHþ 4 -N and NO -N in the filtered extracts by using standard methods 3
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(Norman and Stucki, 1981; Searle, 1984). The soil moisture was detected by drying with constant weight in an oven under 105 °C for 24 h. 3. Results and discussion 3.1. Effect of DMPP on NO 3 -N concentration in leachate
Silt loam soil
35.0 30.0
UA
25.0
DP CK
-1
NO3-N (mg column )
The application of urea in the soil increased the concentrations of NO 3 -N in the leachate compared to those of CK treatment (Fig. 1). Under the UA treatment, the observed peaks of NO 3 -N in leachate appeared on day 20 in both soils, with the maximum levels of 11.4 mg l1 in the silt loam soil and 10.9 mg l1 in the heavy clay soil. Under CK treatments, the maximum levels of NO 3 -N observed in silt loam soil and heavy clay soil were less than 1.3 mg l1 and 0.3 mg l1, respectively. A slower declining tendency of NO 3 -N in both soils was found from day 20 to day 60, but the NO 3 -N concentration was still higher than 7.0 mg l1. Under the DP treatment, the concentrations of NO 3 -N in the leachate showed a declining tendency within the first 30 or 40 days, e.g. from 2.9 mg l1 on day 10 to 1.9 mg l1 on day 30 in the silt loam soil and 3.1 mg l1 on day 10 to 1.4 mg l1 on day 40 in the heavy clay soil. Thereafter, the NO 3 -N concentrations were increased slowly over time, and finally reached 4.0 mg l1 in the silt loam soil and 3.6 mg l1 in the heavy clay soil on day 60. It is obvious that the concentrations of NO 3 -N under DP
treatment in both soils were far lower than those under UA treatment consistently because of NI DMPP addition. Generally, WHO standards reveal that NO 3 -N concentration below 10 mg l1 is suitable for drinking and pose no health risk. With regard to this standard, regular urea application could increase some potential NO 3 -N pollution to shallow groundwater. However, when DMPP was used, the NO 3 -N concentrations in leachate were greatly reduced and decreased the pollution risk to shallow groundwater enormously. The accumulative losses of soil NO 3 -N in leaching over time are shown in Fig. 2. The accumulative NO 3 -N loss in the CK treatment was considerably low within the whole period observed, and 1.8 mg and 0.6 mg of NO 3 -N were lost in columns filled with the silt loam soil and heavy clay soil within 60 day, respectively. However the accumulative losses of soil NO 3 -N leaching were increased largely in soil applied with regular urea, accounting 31.6 mg and 29.8 mg losses in the silt loam soil and heavy clay soil at the end of day 60, respectively, which were 29.8 mg and 29.2 mg higher than those under the corresponding CK treatment. However, under the DP treatment, the total losses of soil NO 3 -N via leaching reached 10.5 mg and 9.1 mg in the silt loam soil and heavy clay soil, which were increased over
Silt loam soil
14.0
UA DP CK
-1
NO3-N (mg l )
12.0 10.0 8.0 6.0 4.0
20.0 15.0 10.0 5.0
2.0
0.0
0.0
10 0
10
20
30
40
50
20
30
60
Days
40
50
60
50
60
Days Heavy clay soil
-1
Heavy clay soil
UA DP CK
10.0
-1
NO3-N (mg l )
12.0
NO3-N (mg column )
35.0
8.0 6.0 4.0 2.0
30.0
UA DP CK
25.0 20.0 15.0 10.0 5.0
0.0
0.0 0
10
20
30
40
50
60
Days Fig. 1. Temporal changes of NO 3 -N concentrations in the leachate of soil columns with 50 cm depths. Data are means ± SD (n = 3). The two different soils in column received with regular urea application at rate of 200 kg N ha1 only (UA); with regular urea application of 200 kg N ha1 combined with 1.0% of 3,4-dimethyl pyrazole phosphate (DMPP) (DP); no application of fertilizer (CK).
10
20
30
40
Days
Fig. 2. The accumulation losses of NO 3 -N in the leachate of soil columns with 50 cm depths. Data are means ± SD (n = 3). The two different soils in column received with regular urea application at rate of 200 kg N ha1 only (UA); with regular urea application of 200 kg N ha1 combined with 1.0% of 3,4-dimethyl pyrazole phosphate (DMPP) (DP); no application of fertilizer (CK).
Q. Yu et al. / Chemosphere 67 (2007) 872–878
Silt loam soil
4.5
UA DP CK
4.0
-1
NH4-N (mg column )
The temporal changes of NHþ 4 -N concentrations in leachate of soil columns were shown in Fig. 3. The leaching NHþ 4 -N concentrations in the silt loam soil under CK treatment, tended to vary slightly. The observed peak of NHþ 4 -N concentrations under UA and DP treatments appeared after ten days with the maximum NHþ 4 -N concentrations of 3.4 mg l1 and 3.5 mg l1, respectively. After 30 days, there was no obvious difference of NHþ 4 -N concentrations among the treatments of CK, UA and DP. A similar trend of NHþ 4 -N concentrations was found in the heavy clay soil. The concentrations of NHþ 4 -N in the leachate decreased dramatically in UA and DP treatments over time from 2.9 mg l1, 3.1 mg l1 on day 10 to 0.4 mg l1, 0.5 mg l1 on day 20, respectively. After 20 days, there was also no remarkable difference for the NHþ 4 -N concentration among the treatments of CK, UA and DP. The accumulative losses of soil NHþ 4 -N through leaching increased over time (Fig. 4). The increasing under the CK treatment took place under very slow rate, and NHþ 4 -N losses of 1.2 mg and 0.9 mg were found in the silt
4.0 3.5
UA DP CK
Silt loam soil
3.0 2.5 2.0 1.5 1.0 0.5 0.0 10
20
30
40
50
60
50
60
Days 3.5 3.0 -1
3.2. Effect of DMPP on NH þ 4 -N concentration in leachate
4.5
NH4-N (mg column )
8.7 mg and 8.6 mg than the corresponding CK treatment, but were reduced by 66.8% and 69.5% of those in the UA treatment, respectively.
875
Heavy clay soil UA DP CK
2.5 2.0 1.5 1.0 0.5 0.0 10
20
30
40
Days
Fig. 4. The accumulation losses of NHþ 4 -N in the leachate of soil columns with 50 cm depths. Data are means ± SD (n = 3). The two different soils in column received with regular urea application at rate of 200 kg N ha1 only (UA); with regular urea application of 200 kg N ha1 combined with 1.0% of 3,4-dimethyl pyrazole phosphate (DMPP) (DP); no application of fertilizer (CK).
-1
NH4-N (mg l )
3.5 3.0 2.5 2.0 1.5 1.0 0.5 0.0 0
10
20
30
40
50
60
Days 4.0
Heavy clay soil UA DP CK
3.0
-1
NH4-N (mg l )
3.5
2.5 2.0 1.5 1.0 0.5 0.0 0
10
20
30
40
50
60
loam soil and heavy clay soil, respectively. The accumulative losses of soil NHþ 4 -N through leaching were increased with the rates of urea-N application, and 3.5 mg and 2.7 mg NHþ 4 -N were lost within 60 days from the silt loam soil and heavy clay soil with regular urea application. Under the DP treatment, the accumulative losses of soil NHþ 4 -N from leachate within 60 days were 3.9 mg and 2.9 mg for silt loam soil and heavy clay soil, respectively; and it was increased over 2.7 mg and 2.0 mg than in respective CK treatment, while it was over 0.3 mg (9.7%) and 0.2 mg (6.7%) increase than under the UA treatment. The results showed, the losses of NHþ 4 -N from leachate increased highly with the urea application, but the total losses of NHþ 4 -N from leachate was still in a low level; and there was no obvious difference between the UA treatment and DP treatment. The reason might contribute to the strong adsorption character of soil colloid for soil NHþ 4 -N, so it can’t be easily transferred with the movement of water.
Days
Fig. 3. Temporal changes of NHþ 4 -N concentrations in the leachate of soil columns with 50 cm depths. Data are means ± SD (n = 3). The two different soils in column received with regular urea application at rate of 200 kg N ha1 only (UA); with regular urea application of 200 kg N ha1 combined with 1.0% of 3,4-dimethyl pyrazole phosphate (DMPP) (DP); no application of fertilizer (CK).
3.3. Effect of DMPP on inorganic-N losses via leaching The total amounts of inorganic-N (NHþ 4 -N and NO -N) leaching during 60 days from the soil columns 3 under DP treatment were 14.3 mg and 12.0 mg in the silt
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loam soil, and the heavy clay soil, respectively. The respectively figures achieved with regular urea treatments (UA) were 35.1 mg and 32.5 mg. Compared to the regular urea application, addition of NI DMPP with urea could effectively reduce 59.3–63.1% of inorganic-N leaching loss. For both minimizing nitrate leaching and chemical fertilizer cost, regular urea applying with additions of 1.0% DMPP may be a good alternative at using large-scale chemical fertilizer. In this experiment, it was found that
the leaching losses of NHþ 4 -N were about ten times lower than those of NO 3 -N. It is implied that the potential of NHþ 4 -N leaching along the soil profile might occur, but not in large quantities, and the NO 3 -N was the predominant form which transferred by vertical water movement (Table 2). In 0–3 cm surface soil layer, treated with NI DMPP, maintained a higher level of NHþ 4 -N and lower level of NO 3 -N as compared to UA treatment during the whole
Table 2 Comparison of leaching losses of inorganic-N from two soil columns Treatments
Silt loam soil
Heavy clay soil NO 3 -N (mg)
NHþ 4 -N (mg) CK UA DP
a
Total IN (mg)
a
1.2 ± 0.6 3.5 ± 0.6a 3.9 ± 0.2a
a
1.7 ± 0.2 31.6 ± 1.7a 10.5 ± 2.3a
2.9 ± 0.2 35.1 ± 1.2a 14.4 ± 2.2a
NHþ 4 -N (mg)
%*
a
58.6 90.0 72.9
NO 3 -N (mg)
Total IN (mg)
a
0.9 ± 0.6 2.7 ± 0.2a 2.9 ± 0.2a
a
0.9 ± 0.2 29.8 ± 1.7a 9.1 ± 0.8a
1.8 ± 0.2 32.5 ± 1.5a 12.0 ± 0.6a
%* 50.0 91.7 75.8
Data are means ± SD (n = 3). The two different soils in column received with regular urea application at rate of 200 kg N ha1 only (UA); with regular urea application of 200 kg N ha1 combined with 1.0% of 3,4-dimethyl pyrazole phosphate (DMPP) (DP); no application of fertilizer (CK). a Numbers followed by a different letter in each sub-column are significantly different at the 0.01 level of probability using Duncan’s multiple range test. * The percent of NO 3 -N in Total inorganic-N.
350
Silt loam soil
400 UA
Heavy clay soil UA
350
DP
250
CK
200 150 100
DP
NH4-N (mg kg-1) (DW)
NH4-N (mg kg-1) (DW)
300
300
CK
250 200 150 100
50
50 0
0 0
10
20
30
40
50
0
60
10
20
60.0
60.0
40
50
60
Heavy clay soil
Silt loam soil
UA
UA
50.0
50.0
DP
NO3-N (mg kg-1) (DW)
NO3-N (mg kg-1) (DW)
30
Days
Days
CK
40.0
30.0
20.0
10.0
DP CK
40.0
30.0
20.0
10.0
0.0
0.0 0
10
20
30
Days
40
50
60
0
10
20
30
40
50
60
Days
Fig. 5. NHþ 4 -N and NO3 -N concentrations in surface layer (0–3 cm) soils at different periods. according to dry weigh (DW) calculation of soil. Data are means ± SD (n = 3). The two different soils in column received with regular urea application at rate of 200 kg N ha1 only (UA); with regular urea application of 200 kg N ha1 combined with 1.0% of 3,4-dimethyl pyrazole phosphate (DMPP) (DP); no application of fertilizer (CK).
Q. Yu et al. / Chemosphere 67 (2007) 872–878
cabbage growth periods (Fig. 5). These results indicated that NI DMPP could effectively retard the process of NHþ 4 -N oxidization to NO3 -N within 60 days in the silt loam soil and heavy clay soil. A lower nitrate concentration in the upper soil could effectively minimize the NO 3 -N leaching loss, and the N2O emission would also be decreased (Fettweis et al., 2001; Linzmeier et al., 2001; Weiske et al., 2001). The leachate sampled from silt loam soil column had higher concentrations of NO 3 -N and lower levels of NHþ 4 -N than those sampled from the heavy clay soil column, after application of regular urea. The similar tendencies existed in leachate after urea application with NI DMPP addition. The discrepancies in accumulaþ tion of NO 3 -N and NH4 -N were likely related to the soil properties (Table 1), which will influence the nitrification and transformation during the experiment period. Firstly, in comparison with the silt loam soil, the characteristics of the heavy clay soil possessed higher density in texture (Table 1) and higher organic C in the column experiment. The heavy clay soil might have resulted in lower redox potential, and subsequently might have retarded nitrification, compared with the silt loam soil. Secondly, the heavy clay soil has a higher cation exchange capacity than the silt loam soil, and therefore might have a higher NHþ 4 -N sorption and lower transformation of NHþ -N, but then lower 4 NHþ -N concentration in leachate of heavy clay soil. 4 Thirdly, in comparison with the silt loam soil, the characteristics of the heavy clay soil possessed higher water holding capacity in the soil column experiment. The heavy clay soil might have resulted in more water content in the column and subsequently might decrease the concentrations þ and leaching losses of NO 3 -N and NH4 -N in the leachate with the water replacement process, compared with the silt loam soil. The leaching loss of nitrate in DP treatment is not in a higher level after 60 days. Firstly, our simulations demonstrate that the cabbage uptake fractions varied considerably among the different treatments. The amount of N uptake by cabbage under the CK treatment was in a low level, and only 72.9 mg and 81.4 mg were found in the silt loam soil and heavy clay soil treatments, respectively. With regular urea application, 161.2 mg and 177.5 mg were absorbed by cabbage within 60 days under the silt loam soil and heavy clay soil treatments. Under the DP treatment, the amount of N uptake within 60 days were 230.0 mg and 295.2 mg; increased 68.8 mg (42.7%) and 117.7 mg (66.3%) than that of UA treatments in the silt loam soil and heavy clay soil, respectively. The results showed that the N uptake significantly increased with the DMPP addition, and most of the N was absorbed in the form of NHþ 4 -N by the cabbage in the DP treatment (Prasad and Power, 1995). So, from the N mass balance view, the leaching loss of inorganic N is weak, no significant leaching is expected in DP treatment after 60 days since most of N has been absorbed by the cabbage. Secondly, on day 60, the NHþ 4 -N concentration was in a low level in soil under the DP treatment (Fig. 5). Much NO 3 -N could not be
877
formed by ammonium oxidization process in soil without sufficient NHþ 4 -N, thus resulting in low nitrate concentration in soil after 60 days. Thirdly, the cabbage had strong root system in soil after 30 days, which strengthened the ability to absorb nitrate from the deep soil and decrease the vertical movement. In the present experiment, we also found that the fresh yields and dry weights of cabbage under the DP treatment were increased, the total N uptake was also increased, while the NO 3 -N level in cabbage was significantly decreased, and no phytotoxicity phenomenon appeared (data not shown). 4. Conclusions In the early stage before day 20 or 30, the concentrations of NHþ 4 -N in leachate after DMPP application were slightly high, but there were no differences in the latter periods compared with the treatments without DMPP addition. The pollution risk of NHþ 4 -N leaching to shallow groundwater could effectively be avoided under DP treatment because of the strong absorption for NHþ 4 -N by soil. The nitrate concentrations in the shallow groundwater may exceed 10 mg l1 when applying regular urea at the rate of 200 kg N ha1 to the silt loam soil and heavy clay soil, easily contributing the nitrate pollution in the early stage. But the corresponding NO 3 -N concentrations were greatly reduced and consequently lowered the NO 3 -N losses through leaching once urea applying with 1.0% content of NI DMPP. The incorporation of nitrification inhibitor to the urea-N chemical fertilizer can reduce about 59.3–63.1% of total inorganic-N losses via leaching, thus minimizing the risk of NO 3 -N pollution in shallow groundwater. Since experiments were conducted under controlled glass house conditions, it requires further testing under field conditions. Acknowledgement We are grateful for support from the Major State Basic Research and Development Program of the People’s Republic of China (Code of Program: 2002CB410807). References Adams, P.L., Daniel, T.C., Edwards, D.R., Nichols, D.J., Pote, D.H., Scott, H.D., 1994. Poultry litter and manure contributions to nitrate leaching through the vadose zone. Soil Sci. Soc. Am. J. 58, 1206–1211. Amberger, A., 1989. Research on dicyandiamide as a nitrification inhibitor and future outlook. Commun. Soil Sci. Plan. 20, 1933–1995. Bray, R.H., Kurtz, L.T., 1945. Determination of total organic and available form of P in soil. Soil Sci. 59, 39–45. Bremner, J.M., 1965. Total nitrogen. In: Black, C.A. (Ed.), Methods of Soil Analysis, . In: Part 2. Am. Soc. Agron. Madison, Wisconsin, USA, pp. 1149–1178. Bronson, K.F., Moiser, A.R., Bishnoi, S.R., 1992. Nitrous oxide emission in irrigated corn as affected by nitrification inhibitor. Soil Sci. Soc. Am. J. 56, 161–165. Chang, C., Entz, T., 1996. Nitrate leaching losses under repeated cattle feedlot manure applications in Southern Alberta. J. Environ. Qual. 25, 145–153.
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Chapman, H.D., 1965. Cation exchange capacity. In: Black, C.A., Evans, D.D., White, J.L. (Eds.), Methods of Soil Analysis, . In: Part 2. Am. Soc. Agron. Madison, Wisconsin, USA, pp. 891–901. Chen, X.M., Shen, Q.R., Pan, G.X., Liu, Z.P., 2003. Characteristics of nitrate horizontal transport in a paddy field of the Tai Lake Region in China. Chemosphere 50, 703–706. Delgado, J.A., Mosier, A.R., Follett, R.H., Westfall, D., Vermeulen, J., Klemedtsson, L., 1996. Effect of N management on N2O and CH4 fluxes and N recovery in an irrigated mountain meadow. Nutr. Cycl. Agroecosys. 46, 127–134. Fettweis, U., Mittelstaedt, W., Schimansky, C., Fuhr, F., 2001. Lysimeter experiments on the translocation of the carbon-14-labelled nitrification inhibitor 3,4-dimethyl pyrazole phosphate (DMPP) in a gleyic cambisol. Biol. Fert. Soils 34, 126–130. Fraters, D., Leo, J.M., Wim, D., 1998. Nitrogen monitoring in groundwater in the sandy regions of the Netherlands. Environ. Pollut. 102, 479–485. Groeneveld, R., Bouwman, A.F., Kruitwagen, S., Van Ierland, E.C., 1998. Nitrate leaching in dairy farming: economic effects of environmental restrictions. Environ. Pollut. 102, 755–761. Hauck, R.D., 1980. Mode of action of nitrification inhibitors. In: Meisinger, J.J., Randall, G.W., Vitosh, M.L., Stelly, M., Kroll, D.M., Cousin, M.K. (Eds.), Nitrification Inhibitors Potentials and Limitations. Am. Soc. Agron. Madison, Wisconsin, U.S.A., pp. 19–32. Irigoyen, I., Muro, J.M., Azpilikueta, M., Aparicio-Tejo, P., Lamsfus, C., 2003. Ammonium oxidation kinetics in the presence of nitrification inhibitors DCD and DMPP at various temperatures. Aust. J. Soil Res. 41, 1177–1183. Insaf, S.B., Mohamed, A.A., Mohamed, H., Terao, K.K., Keiichi, O., 2004. Assessment of groundwater contamination by nitrate leaching from intensive vegetable cultivation using geographical information system. Environ. Int. 29, 1009–1017. Julie, C., Williamson, M.D., Taylor, R.S., Torrens, M., 1998. Reducing nitrogen leaching from dairy farm effluent-irrigated pasture using dicyandiamide: a lysimeter study. Agr. Ecosyst. Environ. 69, 81–88. Kurtz, L.T., 1980. Potential for nitrogen loss. In: Meisinger, J.J., Randall, G.W., Vitosh, M.L., Stelly, M., Kroll, D.M., Cousin, M.K. (Eds.), Nitrification Inhibitors-Potentials and Limitations. Am. Soc. Agron. Madison, Wisconsin, U.S.A., pp. 1–17. Linzmeier, W., Guster, R., Schmidhalter, U., 2001. Nitrous oxide emission from soil and from a nitrogen-15 labeled fertilizer with the nitrification inhibitor 3,4-dimethyl pyrazole phosphate (DMPP). Biol. Fert. Soils 34, 103–108.
Liu, H.B., Zhang, Y.G., Li, Z.H., Zhang, W.L., Lin, B., 2005. Nitrate contamination of deep groundwater in rural plain areas of Beijing. Acta. Pedol. Sin. 42, 411–417, in Chinese. Lyle, P., Richard, G., 1997. Nitrate leaching using two potato-corn Nfertilizer plans on sandy soil. Agr. Ecosyst. Environ. 65, 1–13. Morihiro, M., Zhao, B.Z., Ozaki, Y., Tadakatsu, Y., 2003. Nitrate leaching in an Andisol treated with different types of fertilizers. Environ. Pollut. 121, 477–487. Murphy, J., Rilley, J.P., 1962. A modified single solution method for the determination of phosphate in natural waters. Anal. Chem. Acta. 27, 31–36. Norman, R.J., Stucki, J.W., 1981. The determination of nitrate and nitrite in soil extracts by ultraviolet spectrophotometry. Soil Sci. Soc. Am. J. 45, 347–353. Prasad, R., Power, J.F., 1995. Nitrification inhibitors for agriculture, health, and the environment. Adv. Agron. 54, 233–281. Preibe, D.L., Blackmer, A.M., 1989. Preferential movement of oxygen-18labelled water and nitrogen-15-labelled urea through macrospores in a Nicollet soil. J. Environ. Qual. 18, 66–72. Searle, P.L., 1984. The Berthelot or indophenol reaction and its use in the analytical chemistry of nitrogen-A review. Analyst. 109, 549–568. Serna, M.D., Banuls, J., Quifiones, A., Primo Millo, E., Legaz, F., 2000. Evaluation of 3, 4-dimentylphyrazole phosphate as a nitrification inhibitor in a Citrus cultivated soil. Biol. Fert. Soils. 32, 41–46. Shen, Q.R., Ran, W., Cao, Z.H., 2003. Mechanisms of nitrite accumulation occurring in soil nitrification. Chemosphere 50, 747–753. Thomsen, I.K., Hansen, J.F., Kjellerup, V., Christensen, B.T., 1993. Effects of cropping system and rates of nitrogen in animal slurry and mineral fertilizer on nitrate leaching from a sandy loam. Soil Use. Manage. 9, 53–58. Walkey, A., Black, A., 1934. Determination of organic matter. Soil Sci. 37, 29–38. Weiske, A., Benckiser, G., Herbert, T., Ottow, J., 2001. Influence of the 3,4-dimethyl pyrazole phosphate (DMPP) in comparison to dicyandiamide (DCD) on nitrous oxide emission, carbon dioxide fluxes and methane oxidation during 3 years of repeated application in field experiments. Biol. Fert. Soils. 34, 109–117. Zerulla, W., Barth, T., Dressel, J., Erhardt, K., Horcher von locquenghien, K., Pasda, G., Mwissemeier, Ra¨dle, 2001. 3,4-dimethyphyrazle phosphate: a new nitrification inhibitor for agriculture and horticulture. Biol. Fert. Soils. 34, 118–125. Zhu, J.G., Liu, G., Han, Y., Zhang, Y.L., Xing, G.X., 2003. Nitrate distribution and denitrification in the saturated zone of paddy field under rice/wheat rotation. Chemosphere. 50, 725–732.
Evaluation of nitrification inhibitor 3,4-dimethyl pyrazole phosphate on nitrogen leaching in undisturbed soil columns Qiaogang Yu a, Yingxu Chen a
a,*
, Xuezhu Ye b, Qiuling Zhang a, Zhijian Zhang a, Ping Tian
a
Department of Environmental Engineering, Zhejiang University, Hangzhou 310029, China b Zhejiang Academy of Agricultural Sciences, Hangzhou 310021, China
Received 30 June 2006; received in revised form 5 November 2006; accepted 8 November 2006 Available online 4 January 2007
Abstract The application of nitrogen fertilizers leads to various ecological problems such as nitrate leaching. The use of nitrification inhibitors (NI) as nitrate leaching retardants is a proposal that has been suggested for inclusion in regulations in many countries. In this study, the efficacy of the new NI, 3,4-dimethyl pyrazole phosphate (DMPP), was tested under simulated high-risk leaching situations in two types of undisturbed soil columns. The results showed that the accumulative leaching losses of soil nitrate under treatment of urea with 1.0% DMPP, from columns of silt loam soil and heavy clay soil, were 66.8% and 69.5% lower than those soil columns tested with regular urea application within the 60 days observation, respectively. However, the losses of ammonium leaching were reversely increased 9.7% and 6.7% under the former treatment than the latter one. Application of regular urea with 1.0% DMPP addition can reduce about 59.3%– 63.1% of total losses of inorganic nitrogen via leaching. The application of DMPP to urea had stimulated the inhibition effects of DMPP on the ammonium nitrification process in the soil up to 60 days. It is proposed that the DMPP could be used as an effective NI to control inorganic N leaching losses, minimizing the risk of nitrate pollution in shallow groundwater. Ó 2006 Elsevier Ltd. All rights reserved. Keywords: 3,4-Dimethyl pyrazole phosphate; Nitrification inhibitor; Nitrate leaching; Nitrate pollution; Nitrogen fertilizer
1. Introduction Nitrate leaching from arable land, which causes contamination of groundwater, has become a worldwide environmental concern. In rural plain areas of Beijing, nitrate-N 1 (NO were found 3 -N) concentrations exceeding 10 mg l in above 20% of the investigated groundwater samples in 2000 (Liu et al., 2005). Excessive use of readily available conventional chemical fertilizers to agriculture land is the main source of groundwater contamination (Thomsen et al., 1993; Adams et al., 1994; Chang and Entz, 1996; Fraters et al., 1998). The nitrate concentrations of groundwater under vegetable fields were significantly higher than those under the urban land or paddy fields (Lyle and Rich*
Corresponding author. Tel.: +86 571 86971159; fax: +86 571 86971898. E-mail address: [email protected] (Y. Chen). 0045-6535/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.chemosphere.2006.11.016
ard, 1997; Groeneveld et al., 1998; Insaf et al., 2004). The vegetable fields were considered as the principal source of groundwater nitrate contamination. To reduce nitrate leaching from agriculture land, one of the proposals currently being considered for inclusion in regulations is the use of slow-release fertilizers, especially for using the fertilizer added with new-type nitrification inhibitors (NI) (Chen et al., 2003; Morihiro et al., 2003). However, little information is available on the efficacy of chemical fertilizers applying with additions of NI in order to reduce nitrate leaching to the groundwater in China. In temperate soils, ammonium is strongly adsorbed to cation exchange sites, whilst nitrate is highly mobile within the soil column. NI are compounds that delay oxidation of the ammonium ion (NHþ 4 Þ to nitrate by suppressing the activity of Nitrosomonas spp. bacteria (Hauck, 1980; Irigoyen et al., 2003). NI can, therefore, theoretically reduce nitrate leaching by retaining nitrogen (N) in a form of
Q. Yu et al. / Chemosphere 67 (2007) 872–878
low mobility (e.g. ammonium-N) (Kurtz, 1980; Shen et al., 2003). On the other hand, NI decrease nitrate concentration in soil, and as a result, they also decrease N losses through run off (Fettweis et al., 2001) and denitrification (Bronson et al., 1992; Delgado et al., 1996; Weiske et al., 2001; Zhu et al., 2003). When the N-use efficiency is improved, and N doses and the rate of fertilizing applications are decreased, both economic and environmental benefits are achieved. A lot of chemical material, both natural and synthetic, shows nitrification-inhibiting capabilities (Prasad and Power, 1995). Commercially available N fertilizers incorporate dicyandiamide (DCD) and nitrapyin (Amberger, 1989), and recently, 3,4-dimethyl pyrazole phosphate (DMPP ) has also been used in agriculture crops (Prasad and Power, 1995; Serna et al., 2000). Generally, DCD is just too expensive for large-scale use in agriculture, and its efficiency is comparatively low, even resulting in phytotoxicity problems under certain climate conditions (Zerulla et al., 2001). Moreover, nitrapyin belongs to the group of organic chlorine compounds, and the release of nitrapyin into the environment faces the increasing opposition because it poses certain toxicological problems (Zerulla et al., 2001). On the contrary, DMPP belongs to a chemical group that has been demonstrated to be very efficient in inhibiting the nitrification process in the soil, and was found no toxicological and eco-toxicological side-effect based on extensive standard toxicology and eco-toxicology tests (Zerulla et al., 2001). At present, there are few studies on the effect of DMPP on the reduction of N leaching from vegetable fields. In this study, undisturbed soil columns were used to illustrate the effect of the DMPP on inorganic N loss by simulating leaching condition of vegetable fields. 2. Materials and methods 2.1. Experimental soils Two experimental soils for this study were sampled from the southeast of China. The silt loam soil is collected from Jianggang Town (120.2E, 30.3N), Hangzhou City, Zhejiang Province where the tested soil in the site is classified as the permeable type with a texture of loam silt. Heavy clay soil is collected from the Taihu Basin Region, Jiaxing City (120.7E, 30.8N) where the tested soil is classified as the waterlogged type derived from clay loam deposit. The profile structures of these two soils were also different: the former with a relative uniform and permeable profile while the latter without this layer but with tight impermeable layer of acclimated clay. The basic properties of the experimental soil are shown in Table 1. 2.2. Experimental design The undisturbed soil columns were collected similar to the mortar encasement method of (Preibe and Blackmer, 1989). Briefly, soil was excavated from around a free-standing cylindrical soil column of 16 cm diameter by 50 cm
873
Table 1 Some physical and chemical properties of the two soils used in the experiment Parameter
Silt loam soil
Soil depth (cm)
0–15
15–30
30–50
0–15
15–30
30–50
1.88 0.74 20.4 9.88 7.38 29.0 62.7 8.3
1.42 0.66 15.1 9.07 7.12 24.5 66.1 9.4
0.88 0.57 4.8 6.65 7.15 20.7 69.2 10.1
2.43 0.93 23.1 18.25 6.83 46.4 42.1 11.5
1.73 0.79 19.8 18.13 6.96 46.1 44.2 9.7
0.97 0.62 7.7 16.98 7.06 50.3 41.9 7.8
1 a
Total N (g kg ) Total P (g kg1)b Organic C (g kg1)c CEC (cmol kg1)d pHe Clay (%) Silt (%) Sand (%) a b c d e
Heavy clay soil
Bremner (1965). Bray and Kurtz (1945) and Murphy and Rilley (1962). Walkey and Black (1934). Chapman (1965). Soil to water ratio of 1:2.5.
depth. When the soil columns were properly shaped, a polyvinyl chloride (PVC) pipe of 20 cm diameter was placed around the columns, and liquefied petroleum jelly was placed in the space between the soil and the PVC, to prevent edge-flow (Julie et al., 1998). Then the encased soil columns were brought to laboratory for testing. The total pore space and water holding capacity in the silt loam soil column were 41.5% and 30.3%, while those in the heavy clay soil column were 58.6% and 38.4%, respectively. The soil in the 0–3 cm upper part of the column was also from the original field layer 0–5 cm, but was subjected to one of the following treatments with three replicates: (1) no application of fertilizer (control, designated as CK), (2) regular urea application at rate of 200 kg N ha1 only (designated as UA), and (3) application at rate of 200 kg N ha1 added with 1.0% of DMPP (w/w) (designated as DP). Each undisturbed soil column was cultivated with a common regional crop of Cabbage (Brassica campastris L. ssp. pekinesis) which was transplanted with seeding-growth before fertilizer application. The leaching experiment was conducted under the temperature of 18–22 °C and the humidity of 65% in an artificial glasshouse in Zhejiang University. During the period of leaching experiment, 70 ml of distilled water was applied daily from the top of each soil columns representing local daily rainfall, transpiration and evaporation requirements. Soil solution samples were collected from the bottom of soil column at an interval of ten days. 2.3. Sample analysis Water samples were stored in dark at 4 °C in an icebox prior to analyze. The concentrations of NHþ 4 -N and NO -N in leachate were determined by using ion chroma3 tography (IC 20, Dionex, USA), and the Ultraviolet Spectrophotomery (Norman and Stucki, 1981), respectively. The fresh soil samples were extracted by shaking with 2 M KCl at a soil/solution ratio of 1:5 for 30 min, filtering, and then determining the concentration of NHþ 4 -N and NO -N in the filtered extracts by using standard methods 3
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(Norman and Stucki, 1981; Searle, 1984). The soil moisture was detected by drying with constant weight in an oven under 105 °C for 24 h. 3. Results and discussion 3.1. Effect of DMPP on NO 3 -N concentration in leachate
Silt loam soil
35.0 30.0
UA
25.0
DP CK
-1
NO3-N (mg column )
The application of urea in the soil increased the concentrations of NO 3 -N in the leachate compared to those of CK treatment (Fig. 1). Under the UA treatment, the observed peaks of NO 3 -N in leachate appeared on day 20 in both soils, with the maximum levels of 11.4 mg l1 in the silt loam soil and 10.9 mg l1 in the heavy clay soil. Under CK treatments, the maximum levels of NO 3 -N observed in silt loam soil and heavy clay soil were less than 1.3 mg l1 and 0.3 mg l1, respectively. A slower declining tendency of NO 3 -N in both soils was found from day 20 to day 60, but the NO 3 -N concentration was still higher than 7.0 mg l1. Under the DP treatment, the concentrations of NO 3 -N in the leachate showed a declining tendency within the first 30 or 40 days, e.g. from 2.9 mg l1 on day 10 to 1.9 mg l1 on day 30 in the silt loam soil and 3.1 mg l1 on day 10 to 1.4 mg l1 on day 40 in the heavy clay soil. Thereafter, the NO 3 -N concentrations were increased slowly over time, and finally reached 4.0 mg l1 in the silt loam soil and 3.6 mg l1 in the heavy clay soil on day 60. It is obvious that the concentrations of NO 3 -N under DP
treatment in both soils were far lower than those under UA treatment consistently because of NI DMPP addition. Generally, WHO standards reveal that NO 3 -N concentration below 10 mg l1 is suitable for drinking and pose no health risk. With regard to this standard, regular urea application could increase some potential NO 3 -N pollution to shallow groundwater. However, when DMPP was used, the NO 3 -N concentrations in leachate were greatly reduced and decreased the pollution risk to shallow groundwater enormously. The accumulative losses of soil NO 3 -N in leaching over time are shown in Fig. 2. The accumulative NO 3 -N loss in the CK treatment was considerably low within the whole period observed, and 1.8 mg and 0.6 mg of NO 3 -N were lost in columns filled with the silt loam soil and heavy clay soil within 60 day, respectively. However the accumulative losses of soil NO 3 -N leaching were increased largely in soil applied with regular urea, accounting 31.6 mg and 29.8 mg losses in the silt loam soil and heavy clay soil at the end of day 60, respectively, which were 29.8 mg and 29.2 mg higher than those under the corresponding CK treatment. However, under the DP treatment, the total losses of soil NO 3 -N via leaching reached 10.5 mg and 9.1 mg in the silt loam soil and heavy clay soil, which were increased over
Silt loam soil
14.0
UA DP CK
-1
NO3-N (mg l )
12.0 10.0 8.0 6.0 4.0
20.0 15.0 10.0 5.0
2.0
0.0
0.0
10 0
10
20
30
40
50
20
30
60
Days
40
50
60
50
60
Days Heavy clay soil
-1
Heavy clay soil
UA DP CK
10.0
-1
NO3-N (mg l )
12.0
NO3-N (mg column )
35.0
8.0 6.0 4.0 2.0
30.0
UA DP CK
25.0 20.0 15.0 10.0 5.0
0.0
0.0 0
10
20
30
40
50
60
Days Fig. 1. Temporal changes of NO 3 -N concentrations in the leachate of soil columns with 50 cm depths. Data are means ± SD (n = 3). The two different soils in column received with regular urea application at rate of 200 kg N ha1 only (UA); with regular urea application of 200 kg N ha1 combined with 1.0% of 3,4-dimethyl pyrazole phosphate (DMPP) (DP); no application of fertilizer (CK).
10
20
30
40
Days
Fig. 2. The accumulation losses of NO 3 -N in the leachate of soil columns with 50 cm depths. Data are means ± SD (n = 3). The two different soils in column received with regular urea application at rate of 200 kg N ha1 only (UA); with regular urea application of 200 kg N ha1 combined with 1.0% of 3,4-dimethyl pyrazole phosphate (DMPP) (DP); no application of fertilizer (CK).
Q. Yu et al. / Chemosphere 67 (2007) 872–878
Silt loam soil
4.5
UA DP CK
4.0
-1
NH4-N (mg column )
The temporal changes of NHþ 4 -N concentrations in leachate of soil columns were shown in Fig. 3. The leaching NHþ 4 -N concentrations in the silt loam soil under CK treatment, tended to vary slightly. The observed peak of NHþ 4 -N concentrations under UA and DP treatments appeared after ten days with the maximum NHþ 4 -N concentrations of 3.4 mg l1 and 3.5 mg l1, respectively. After 30 days, there was no obvious difference of NHþ 4 -N concentrations among the treatments of CK, UA and DP. A similar trend of NHþ 4 -N concentrations was found in the heavy clay soil. The concentrations of NHþ 4 -N in the leachate decreased dramatically in UA and DP treatments over time from 2.9 mg l1, 3.1 mg l1 on day 10 to 0.4 mg l1, 0.5 mg l1 on day 20, respectively. After 20 days, there was also no remarkable difference for the NHþ 4 -N concentration among the treatments of CK, UA and DP. The accumulative losses of soil NHþ 4 -N through leaching increased over time (Fig. 4). The increasing under the CK treatment took place under very slow rate, and NHþ 4 -N losses of 1.2 mg and 0.9 mg were found in the silt
4.0 3.5
UA DP CK
Silt loam soil
3.0 2.5 2.0 1.5 1.0 0.5 0.0 10
20
30
40
50
60
50
60
Days 3.5 3.0 -1
3.2. Effect of DMPP on NH þ 4 -N concentration in leachate
4.5
NH4-N (mg column )
8.7 mg and 8.6 mg than the corresponding CK treatment, but were reduced by 66.8% and 69.5% of those in the UA treatment, respectively.
875
Heavy clay soil UA DP CK
2.5 2.0 1.5 1.0 0.5 0.0 10
20
30
40
Days
Fig. 4. The accumulation losses of NHþ 4 -N in the leachate of soil columns with 50 cm depths. Data are means ± SD (n = 3). The two different soils in column received with regular urea application at rate of 200 kg N ha1 only (UA); with regular urea application of 200 kg N ha1 combined with 1.0% of 3,4-dimethyl pyrazole phosphate (DMPP) (DP); no application of fertilizer (CK).
-1
NH4-N (mg l )
3.5 3.0 2.5 2.0 1.5 1.0 0.5 0.0 0
10
20
30
40
50
60
Days 4.0
Heavy clay soil UA DP CK
3.0
-1
NH4-N (mg l )
3.5
2.5 2.0 1.5 1.0 0.5 0.0 0
10
20
30
40
50
60
loam soil and heavy clay soil, respectively. The accumulative losses of soil NHþ 4 -N through leaching were increased with the rates of urea-N application, and 3.5 mg and 2.7 mg NHþ 4 -N were lost within 60 days from the silt loam soil and heavy clay soil with regular urea application. Under the DP treatment, the accumulative losses of soil NHþ 4 -N from leachate within 60 days were 3.9 mg and 2.9 mg for silt loam soil and heavy clay soil, respectively; and it was increased over 2.7 mg and 2.0 mg than in respective CK treatment, while it was over 0.3 mg (9.7%) and 0.2 mg (6.7%) increase than under the UA treatment. The results showed, the losses of NHþ 4 -N from leachate increased highly with the urea application, but the total losses of NHþ 4 -N from leachate was still in a low level; and there was no obvious difference between the UA treatment and DP treatment. The reason might contribute to the strong adsorption character of soil colloid for soil NHþ 4 -N, so it can’t be easily transferred with the movement of water.
Days
Fig. 3. Temporal changes of NHþ 4 -N concentrations in the leachate of soil columns with 50 cm depths. Data are means ± SD (n = 3). The two different soils in column received with regular urea application at rate of 200 kg N ha1 only (UA); with regular urea application of 200 kg N ha1 combined with 1.0% of 3,4-dimethyl pyrazole phosphate (DMPP) (DP); no application of fertilizer (CK).
3.3. Effect of DMPP on inorganic-N losses via leaching The total amounts of inorganic-N (NHþ 4 -N and NO -N) leaching during 60 days from the soil columns 3 under DP treatment were 14.3 mg and 12.0 mg in the silt
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loam soil, and the heavy clay soil, respectively. The respectively figures achieved with regular urea treatments (UA) were 35.1 mg and 32.5 mg. Compared to the regular urea application, addition of NI DMPP with urea could effectively reduce 59.3–63.1% of inorganic-N leaching loss. For both minimizing nitrate leaching and chemical fertilizer cost, regular urea applying with additions of 1.0% DMPP may be a good alternative at using large-scale chemical fertilizer. In this experiment, it was found that
the leaching losses of NHþ 4 -N were about ten times lower than those of NO 3 -N. It is implied that the potential of NHþ 4 -N leaching along the soil profile might occur, but not in large quantities, and the NO 3 -N was the predominant form which transferred by vertical water movement (Table 2). In 0–3 cm surface soil layer, treated with NI DMPP, maintained a higher level of NHþ 4 -N and lower level of NO 3 -N as compared to UA treatment during the whole
Table 2 Comparison of leaching losses of inorganic-N from two soil columns Treatments
Silt loam soil
Heavy clay soil NO 3 -N (mg)
NHþ 4 -N (mg) CK UA DP
a
Total IN (mg)
a
1.2 ± 0.6 3.5 ± 0.6a 3.9 ± 0.2a
a
1.7 ± 0.2 31.6 ± 1.7a 10.5 ± 2.3a
2.9 ± 0.2 35.1 ± 1.2a 14.4 ± 2.2a
NHþ 4 -N (mg)
%*
a
58.6 90.0 72.9
NO 3 -N (mg)
Total IN (mg)
a
0.9 ± 0.6 2.7 ± 0.2a 2.9 ± 0.2a
a
0.9 ± 0.2 29.8 ± 1.7a 9.1 ± 0.8a
1.8 ± 0.2 32.5 ± 1.5a 12.0 ± 0.6a
%* 50.0 91.7 75.8
Data are means ± SD (n = 3). The two different soils in column received with regular urea application at rate of 200 kg N ha1 only (UA); with regular urea application of 200 kg N ha1 combined with 1.0% of 3,4-dimethyl pyrazole phosphate (DMPP) (DP); no application of fertilizer (CK). a Numbers followed by a different letter in each sub-column are significantly different at the 0.01 level of probability using Duncan’s multiple range test. * The percent of NO 3 -N in Total inorganic-N.
350
Silt loam soil
400 UA
Heavy clay soil UA
350
DP
250
CK
200 150 100
DP
NH4-N (mg kg-1) (DW)
NH4-N (mg kg-1) (DW)
300
300
CK
250 200 150 100
50
50 0
0 0
10
20
30
40
50
0
60
10
20
60.0
60.0
40
50
60
Heavy clay soil
Silt loam soil
UA
UA
50.0
50.0
DP
NO3-N (mg kg-1) (DW)
NO3-N (mg kg-1) (DW)
30
Days
Days
CK
40.0
30.0
20.0
10.0
DP CK
40.0
30.0
20.0
10.0
0.0
0.0 0
10
20
30
Days
40
50
60
0
10
20
30
40
50
60
Days
Fig. 5. NHþ 4 -N and NO3 -N concentrations in surface layer (0–3 cm) soils at different periods. according to dry weigh (DW) calculation of soil. Data are means ± SD (n = 3). The two different soils in column received with regular urea application at rate of 200 kg N ha1 only (UA); with regular urea application of 200 kg N ha1 combined with 1.0% of 3,4-dimethyl pyrazole phosphate (DMPP) (DP); no application of fertilizer (CK).
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cabbage growth periods (Fig. 5). These results indicated that NI DMPP could effectively retard the process of NHþ 4 -N oxidization to NO3 -N within 60 days in the silt loam soil and heavy clay soil. A lower nitrate concentration in the upper soil could effectively minimize the NO 3 -N leaching loss, and the N2O emission would also be decreased (Fettweis et al., 2001; Linzmeier et al., 2001; Weiske et al., 2001). The leachate sampled from silt loam soil column had higher concentrations of NO 3 -N and lower levels of NHþ 4 -N than those sampled from the heavy clay soil column, after application of regular urea. The similar tendencies existed in leachate after urea application with NI DMPP addition. The discrepancies in accumulaþ tion of NO 3 -N and NH4 -N were likely related to the soil properties (Table 1), which will influence the nitrification and transformation during the experiment period. Firstly, in comparison with the silt loam soil, the characteristics of the heavy clay soil possessed higher density in texture (Table 1) and higher organic C in the column experiment. The heavy clay soil might have resulted in lower redox potential, and subsequently might have retarded nitrification, compared with the silt loam soil. Secondly, the heavy clay soil has a higher cation exchange capacity than the silt loam soil, and therefore might have a higher NHþ 4 -N sorption and lower transformation of NHþ -N, but then lower 4 NHþ -N concentration in leachate of heavy clay soil. 4 Thirdly, in comparison with the silt loam soil, the characteristics of the heavy clay soil possessed higher water holding capacity in the soil column experiment. The heavy clay soil might have resulted in more water content in the column and subsequently might decrease the concentrations þ and leaching losses of NO 3 -N and NH4 -N in the leachate with the water replacement process, compared with the silt loam soil. The leaching loss of nitrate in DP treatment is not in a higher level after 60 days. Firstly, our simulations demonstrate that the cabbage uptake fractions varied considerably among the different treatments. The amount of N uptake by cabbage under the CK treatment was in a low level, and only 72.9 mg and 81.4 mg were found in the silt loam soil and heavy clay soil treatments, respectively. With regular urea application, 161.2 mg and 177.5 mg were absorbed by cabbage within 60 days under the silt loam soil and heavy clay soil treatments. Under the DP treatment, the amount of N uptake within 60 days were 230.0 mg and 295.2 mg; increased 68.8 mg (42.7%) and 117.7 mg (66.3%) than that of UA treatments in the silt loam soil and heavy clay soil, respectively. The results showed that the N uptake significantly increased with the DMPP addition, and most of the N was absorbed in the form of NHþ 4 -N by the cabbage in the DP treatment (Prasad and Power, 1995). So, from the N mass balance view, the leaching loss of inorganic N is weak, no significant leaching is expected in DP treatment after 60 days since most of N has been absorbed by the cabbage. Secondly, on day 60, the NHþ 4 -N concentration was in a low level in soil under the DP treatment (Fig. 5). Much NO 3 -N could not be
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formed by ammonium oxidization process in soil without sufficient NHþ 4 -N, thus resulting in low nitrate concentration in soil after 60 days. Thirdly, the cabbage had strong root system in soil after 30 days, which strengthened the ability to absorb nitrate from the deep soil and decrease the vertical movement. In the present experiment, we also found that the fresh yields and dry weights of cabbage under the DP treatment were increased, the total N uptake was also increased, while the NO 3 -N level in cabbage was significantly decreased, and no phytotoxicity phenomenon appeared (data not shown). 4. Conclusions In the early stage before day 20 or 30, the concentrations of NHþ 4 -N in leachate after DMPP application were slightly high, but there were no differences in the latter periods compared with the treatments without DMPP addition. The pollution risk of NHþ 4 -N leaching to shallow groundwater could effectively be avoided under DP treatment because of the strong absorption for NHþ 4 -N by soil. The nitrate concentrations in the shallow groundwater may exceed 10 mg l1 when applying regular urea at the rate of 200 kg N ha1 to the silt loam soil and heavy clay soil, easily contributing the nitrate pollution in the early stage. But the corresponding NO 3 -N concentrations were greatly reduced and consequently lowered the NO 3 -N losses through leaching once urea applying with 1.0% content of NI DMPP. The incorporation of nitrification inhibitor to the urea-N chemical fertilizer can reduce about 59.3–63.1% of total inorganic-N losses via leaching, thus minimizing the risk of NO 3 -N pollution in shallow groundwater. Since experiments were conducted under controlled glass house conditions, it requires further testing under field conditions. Acknowledgement We are grateful for support from the Major State Basic Research and Development Program of the People’s Republic of China (Code of Program: 2002CB410807). References Adams, P.L., Daniel, T.C., Edwards, D.R., Nichols, D.J., Pote, D.H., Scott, H.D., 1994. Poultry litter and manure contributions to nitrate leaching through the vadose zone. Soil Sci. Soc. Am. J. 58, 1206–1211. Amberger, A., 1989. Research on dicyandiamide as a nitrification inhibitor and future outlook. Commun. Soil Sci. Plan. 20, 1933–1995. Bray, R.H., Kurtz, L.T., 1945. Determination of total organic and available form of P in soil. Soil Sci. 59, 39–45. Bremner, J.M., 1965. Total nitrogen. In: Black, C.A. (Ed.), Methods of Soil Analysis, . In: Part 2. Am. Soc. Agron. Madison, Wisconsin, USA, pp. 1149–1178. Bronson, K.F., Moiser, A.R., Bishnoi, S.R., 1992. Nitrous oxide emission in irrigated corn as affected by nitrification inhibitor. Soil Sci. Soc. Am. J. 56, 161–165. Chang, C., Entz, T., 1996. Nitrate leaching losses under repeated cattle feedlot manure applications in Southern Alberta. J. Environ. Qual. 25, 145–153.
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