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

Abstract

To study the effect of temperature on the soil organic N mineralization of tropical flooded rice soils, laboratory incubation experiments using 30 flooded rice soils from the Philippines, Indonesia, Malaysia, and Thailand were conducted under flooded conditions at 25 and 30°C. The rate of N mineralization was determined every week, but the data at 56 and 112 d were presented and statistically analyzed in this paper. Eleven soil physico-chemical properties were analyzed for correlating with N mineralization. At 112-d incubation, averages of N mineralization were 33 mg N kg−1 at 25°C and 47 mg N kg−1 at 30° C. Average ratios of N mineralization at 30 to 25°C were 1.7 at 56 d, and 1.5 at 112 d. The ratios, however, varied from less than 1 to more than 2. The percentages of N mineralization at 30°C and at 112 d to soil total N content ranged from less than 1 to more than 5, but in two thirds of the cases the values ranked between 2 and 4. Simple correlation coefficients of N mineralization were significant with the properties related to organic matter and soil N (contents of total C, total N, dilute acid soluble carbohydrates, initial NH4+, and microbial biomass N), and to a lesser extent with CEC. Dilute acid-soluble carbohydrate contents was most positively correlated with N mineralization for both temperatures and incubation periods. Contents of soluble carbohydrates, total N, organic C, and sand were introduced into the regressions to predict N mineralization at 25 and 30°C. Predicted values for averages of each independent variable were 16.3±10.4 at 56 d-25°C, 26.7±13.1 at 56 d-30°C, 33.5± 16.8 at 112 d-25°C, and 47.5±18.8 mg N kg−1 at 112 d-30°C. Standard deviations were estimated by the Jackknife method. © 1996, Taylor and Francis Group, LLC.

Source or Periodical Title

Soil Science and Plant Nutrition

ISSN

380768

Page

229-238

Document Type

Article

Subject

Microbial biomass N, Multiple regression, Organic n mineralization, Temperature effects, Tropical wetland rice soil

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