Elsevier

Geoderma

Volume 115, Issues 3–4, August 2003, Pages 161-175
Geoderma

Nitrogen mineralization in paddy soils of the Taihu Region of China under anaerobic conditions: dynamics and model fitting

https://doi.org/10.1016/S0016-7061(02)00358-0Get rights and content

Abstract

The processes and characteristics of nitrogen mineralization in paddy soils of the Taihu Region of China were studied with 120-day anaerobic incubation at 25 and 35 °C. Results showed that the organic nitrogen mineralized ranged from 4.0% to 9.4% of total N (60–241 mg kg−1) and that the mineral N was only correlated with total N (partial correlation analysis). The pH changed greatly and was related to the mineral nitrogen contents during mineralization. Temperature was one of the main factors influencing the mineralization of nitrogen. Four models, (1) effective cumulated temperature model; (2) a one-component, first-order exponential model (one-pool model); (3) a two-component, first-order exponential model (two-pool model); and (4) a two-component, mixed first- and zero-order exponential model including a constant term (special model), were fitted to the observed mineral N vs. incubation days using a non-linear regression procedure. The exponential models were significantly better than the effective cumulated temperature model, and the two-pool model and the special model gave the best fits among the four models. The special model was the unique one that could appropriately reflect the responses of organic nitrogen mineralization to incubation temperature in all studied paddy soils. All results showed that the special model made a better prediction of nitrogen mineralization under flooded conditions than the other models.

Introduction

As the country with the largest population, China takes its food supply as the most important matter. As population increases, there is little likelihood that an adequate food supply under the limited arable land resources can be maintained unless fertilizers are used (Zhu et al., 2000). In 1999, China consumed 2.18×107 mg N of chemical fertilizer (China Agricultural Yearbook, 1999), which accounted for one-fourth of the world's total. However, the N nutrient uptake efficiency by plants was very limited. In general, the plants used only 28–41% of the N fertilizer (Zhu and Wen, 1992). Most of the rest was lost or remained in soil, resulting in direct economic loss to farmers and exerting a negative impact on the atmospheric environment and water quality. In order to make more efficient use of N fertilizers, many kinds of methods and techniques have been used; for example, deciding on an appropriate kind of fertilizer and timing of application (Chu et al., 1978), modifying the application methods by deep placement (Cao and DeDatta, 1983), using slow-release N fertilizer Islam and Person, 1979, Sun et al., 1986 and so on. But the effects of all the methods and techniques were made on the same basis: understanding the N mineralized from soil. So an accurate prediction of the amount of inorganic N released from soil organic matter is essential for the development of farming practices that maximize N use efficiency and minimize adverse impacts of N on the environment (Wang et al., 2001).

In the complex nitrogen turnover in the soil–plant system, mineralization is a key process to be fully understood and taken into account when meeting the N demand of crops (Smith et al., 1977). This process has been studied extensively. In 1972, a one-component, first-order exponential model was used to simulate the dynamics of aerobic long-term mineralization (Stanford and Smith, 1972). Thereafter, other exponential models in different forms were used, such as the double exponential (two-pool) model (Molina, 1980, Richter et al., 1980, Richter et al., 1982, Aviva, 1983; Kazuyuki et al., 1985; Fisher and Parkey, 1987, Rasiah, 1995, Povira and Vallejo, 1997) and the special model Lindemann et al., 1988, Cabrera, 1993, Dou et al., 1995, Roelcke et al., 2002. In the last 30 years, many other models have been used, such as logarithmic models (Narteh and Sahrawat, 2000), parabolic models Broadbent, 1986, Marion and Black, 1987, hyperbolic models (Donald and Mohammas, 1998) and others. However, the exponential models have been used the most frequently. Mineralization is the process of decomposition of organic matter, mediated by soil microbes. Since soil microbial activity is determined by enzyme dynamics, which is often described by an exponential equation (Gao et al., 1984), mineralization should theoretically be described with an exponential equation.

However, all these models were usually used for the upland soils, and only few studies were made with flooded soils. In China, where paddy soils amount to 25% of the total arable land, the study of N mineralization in this type of soils has been an important work. Up until now, only the effective cumulated temperature model has been used to describe the mineralization of flooded soils Yoshino and Die, 1977, Cai et al., 1979, Zhu, 1982, Wang et al., 1983, Tao et al., 1993. This equation has not found international acceptance. Moreover, we found that in the common incubation experiments and analysis methods of nitrogen mineralization in paddy soils, the processes of coupled nitrification and denitrification were ignored, which makes us doubt the accuracy of the description of the mineralization dynamics and of this model as a whole.

The objectives of this study were (1) to study the process and characteristics of organic N mineralization of typical paddy soils with modified anaerobic incubation and (2) to compare the effective cumulated temperature equation with the commonly used exponential equations.

Section snippets

Materials and methods

The Taihu Region (30–31°N, 120–121°E) is one of China's most ancient agricultural regions with a rice cultivation history of several thousand years. It is also one of its most economically developed areas. The climate is warm and moist and has a long growing season. The annual precipitation is 1100–1400 mm, and the mean temperature is approximately 16 °C. The frost-free period is over 230 days. Current agricultural practice in this region is an intensive double-cropping system with irrigated

Results

The mineralized N was dominated by NH4+-N. Some NO3-N was found on days 0 and 1 of incubation only. This initial NO3-N amounted to 30% of inorganic N in all soils except for sample F, in which NO3-N amounted to 60% of the inorganic N. This might have been due to the presence of fertilizer N in the soil at sampling. After 1 day, the NO3-N decreased to 0, meaning the reduction of NO3-N occurred quickly under the incubation conditions.

The cumulative nitrogen mineralization over incubation

Mineral N and mineralization rate

Among the six soils, sample S had the highest amount of mineral N, almost two times that of the other five samples. This phenomenon could be explained by the differences in the physical and chemical properties of the soils. There are many reports on the relationship between mineral capacity and soil properties. In general, the amount of N mineralized is correlated with total N, total C and microbial N Marion et al., 1981, Kafkafi et al., 1983, Dalal and Mayer, 1987, Ireneo et al., 1996,

Conclusions

Because only the effective cumulated temperature model has been used in flooded soil previously, we compared it to the special model in theory and practice. Firstly, the concept of effective cumulative temperature is based on the theory that mineralization is affected by temperature; it does, however, not reflect the essential characteristics of mineralization. The special model explains the process and characteristics of mineralization of two different types of organic matter, and it reflects

Acknowledgements

This research was funded by a grant (G19990118) from the National Natural Science Foundation of China. The comments to the manuscript by Dr. Marco Roelcke, TU Braunschweig, Germany, are gratefully acknowledged.

References (60)

  • G.X. Cai et al.

    Experimental conditions for determining the nitrogen mineralization process during anaerobic incubation of paddy soil

    Turang (Soils)

    (1979)
  • Zh.H. Cao et al.

    Effect of fertilization methods on properties of the water in rice fields and recovery of applied N (15N labeled urea) by lowland rice

    Acta Pedol. Sin.

    (1983)
  • H.D. Chapman

    Cation exchange capacity

  • China Agricultural Yearbook (1999). Agriculture Press, Beijing (in...
  • B.T. Christensen

    Physical fractionation of soil and organic matter in primary partical size and density separates

  • Ch.L. Chu et al.

    Soil nutrition status under “rice–rice–wheat” rotation and the response of rice to fertilizers in Suchow District

    Acta Pedol. Sin.

    (1978)
  • D. Curtin et al.

    Organic matter fractions contribution to soil nitrogen mineralization potential

    Soil Sci. Soc. Am. J.

    (1999)
  • R.C. Dalal et al.

    Long-term trends in fertility of soils under continuous cultivation and cereal cropping in southern Queensland: VII. Dynamics of nitrogen mineralization potentials and microbial biomass

    Aust. J. Soil Res.

    (1987)
  • J.R. Deans et al.

    Models for predicting potentially mineralization nitrogen and decomposition rate constants

    Soil Sci. Soc. Am. J.

    (1986)
  • S. DeNeve et al.

    Temperature effects on C- and N-mineralization from vegetable crop residues

    Plant Soil

    (1996)
  • R.C. Donald et al.

    Nitrogen mineralization in soils from Michigan's Saginaw valley and Thumb region

    Commun. Soil Sci. Plant Anal.

    (1998)
  • R.Z. Donald et al.

    Soil temperature, matric potential and the kinetics of microbial respiration and nitrogen mineralization

    Soil Sci. Soc. Am. J.

    (1999)
  • Zh.X. Dou et al.

    Soil nitrogen mineralization during laboratory incubation: dynamics and model fitting

    Soil Biol. Biochem.

    (1995)
  • B.H. Ellert et al.

    Temperature dependence of net nitrogen and sulfur mineralization

    Soil Sci. Soc. Am. J.

    (1992)
  • F.M. Fisher et al.

    Nitrogen mineralization in a desert soil: interacting effects of soil moisture and nitrogen fertilizer

    Soil Sci. Soc. Am. J.

    (1987)
  • J.H. Gao et al.

    Nitrogen mineralization pattern and nitrogen efficiency in paddy soil

    Acta Pedol. Sin.

    (1984)
  • Y. Han et al.

    Development of an advisory model to reduce nitrogen losses in double-cropping systems in the Taihu Region of China

  • Y. Han et al.

    A deterministic model of the nitrogen cycle in double-cropping systems in the Chinese Taihu Region

  • J.M. Ireneo et al.

    Nitrogen mineralization in tropical wetland rice soils: I. Relationship with temperature and soil properties

    Soil Sci. Plant Nutr.

    (1996)
  • M.S. Islam et al.

    Mineralization of urea and urea derivatives in anaerobic soils

    Plant Soil

    (1979)
  • Cited by (79)

    • Dynamic assessment of the impacts of global warming on nitrate losses from a subsurface-drained rainfed-canola field

      2020, Agricultural Water Management
      Citation Excerpt :

      First, the lack of organic matter (OM) lmits the mineralization process in mineral soils (i.e., soils with OM < 3% in the upper horizon, Huang et al., 2009 cronologically.), as in our study, the lack of OM limits the mineralization process (Li et al., 2003; Deenik, 2006; Wijanarko, 2015). Second, mineralization mainly occurs in coarse-textured soils with low clay content, while it decreases considerably as soil clay content increases (Karandish and Šimůnek, 2017).

    • Two-dimensional modeling of nitrogen and water dynamics for various N-managed water-saving irrigation strategies using HYDRUS

      2017, Agricultural Water Management
      Citation Excerpt :

      Mineralization (N supply) and immobilization (N removal from the mineral N pool) (M&I) are highly dependent on the soil organic matter (OM) and the amount of clay in a soil. Soils with less than 3% of OM in the upper horizon, as in our study, are classified as mineral soils (Huang et al., 2009), in which the M&I processes are often limited due to the lack of OMs (Wijanarko, 2015; Deenik, 2006; Herrmann, 2003; Li et al., 2003). Moreover, mineralization tends to be greater in coarse-textured soils with the low clay content and smaller as the soil clay content increases.

    View all citing articles on Scopus
    View full text