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Soil Carbon and Nitrogen Dynamics in Agricultural Soils of Mymensingh, Bangladesh

Nasrin Islam
Department of Environmental Science, Bangladesh Agricultural University, Mymensingh, Bangladesh

Shahadat Hossen
Department of Environmental Science, Bangladesh Agricultural University, Mymensingh, Bangladesh

Abdul Baten
Department of Environmental Science, Bangladesh Agricultural University, Mymensingh, Bangladesh

Abstract/ Executive Summary:

This study was conducted to evaluate the effect of land uses and soil management practices on the soil organic carbon (SOC) and soil total nitrogen (STN) in different agricultural soils of Mymensigh district located in northern Bangladesh 24°45′14″N 90°24′11″E. The land use types considered were cultivated (single, double and triple cropped), agroforestry, fallow land and grass land. 32 soil samples were collected covering above land use types. SOC and STN were significantly varied in different land use pattern and soil management practices. Among all land use pattern the highest SOC and STN were found under agroforestry and the lowest was found under fallow land. Cropping pattern also influenced the SOC accumulation in soil where rice-fallow-rice cropping pattern had highest SOC accumulation and lowest was found in rice-rice-rice cropping pattern. Organic carbon dynamics highly regulated by organic fertilizer application and tillage operation. The carbon to nitrogen (C: N) ratio was affected by land use systems and the ranges obtained 4.9 to 11.6. The C: N ratio was narrows in different agricultural land use pattern and higher in agroforestry system. The contents of total nitrogen was strongly associated (R² = 0.98) with total organic carbon and decreased consistently with increasing soil depth under all land use systems. The result of this study will help to develop future plan about land use and soil management regarding soil carbon and nitrogen dynamics for better economic returns with environmental protection.

Keywords: Soil Organic Carbon, Soil Total Nitrogen, C: N Ratio, Agroforestry, Fallowland

Location: Mymensigh district

Start Date:

End Date:

Program Area: Crop-Soil-Water Management

Commodity: Soil fertility

Objectives:

To evaluate soil organic carbon and soil total nitrogen in different agricultural field with various land uses and soil management practices.

Methodology:

The location experiences a tropical monsoon-type climate, with a hot and rainy summer, and dry winter. Annual mean air temperature was 25.4°C and the highest mean temperature is reached in the month of April. Annual rainfall was 2055 mm where 70% of the annual rainfall is received during monsoon season (May to August) [14]. The relative humidity varies from 60-98% with some diurnal fluctuations in the various seasons with annual average of 56.8. The area lies within latitude 24°45′14″N and longitude 90°24′11″E of Bangladesh. The soil is darkgray non-calcareous floodplain) with a sandy loam and loam texture texture. Soil Sampling and Analysis- Thirty-six soil samples were collected from twelve different lands covering cropped land, agroforestry, fallow land and grassland. Cropping pattern means the proportion of area under various crops at a point of time in a unit area. We found eight different cropping patterns namely Rice- sunhemp-rice; Rice-fallow-fallow; Rice-Jute-rice; Rice-rice- rice; Rice-aroid-fallow; Rice-fallow-rice; Rice-mustard-rice and Rice-vegetables. In Bangladesh there is three crops growing seasons in a year namely Rabi, pre-kharif and Kharif. In a unit crop land the number of cropping season observed is known as unit cropped land as for example in triple cropped land crop grown all three seasons in a year. The soil sample was taken from the center of each quadrate by driving a core sampler up to 30 cm depth. Soil cores were sectioned into 0-10, 10-20 and 20-30 cm increments for 30 cm samples, then the soil was categorized as top soil (up to 10 cm) and sub soil (up to 30 cm). The soils were collected by an augur and kept in polythene bags so that they remain in field moist condition. Before collecting sample from particular field relevant information regarding fertilizer application and tillage practices was collected from the concern farmer of that field. After completion of collecting soil samples, the unwanted materials like stones, granules, plant parts, leaves, roots etc. were discarded from sample. The samples were dried at room temperature, crushed, mixed thoroughly and sieved with a 2 mm sieve. Composite samples were prepared by mixing the sieved soils and preserved in polythene. Walkley and Black method as modified by Allison [16] was used to determine SOC. The procedure involved the oxidation of the soil organic matter with potassium dichromate (K₂Cr₂O₇) using concentrated sulphuric acid (H₂SO₄) and the percentage OC found by titrating with IN ferrous ammonium sulphate solution. The Kjeldahl method of Bremner [17] using CuSO₄-Na, SO₄ catalyst mixture was used to determine TN. All data were analyzed using SPSS statistical software version 16.0. Analysis of variance (ANOVA) was carried out using two-factor randomized complete plot design. Significant F-values were obtained; differences between individual means were tested using the LSD (Least Significant Difference) test.

Source of Information: International Journal of Agricultural and Biosystems Engineering. Vol. 1, No. 1, 2016, pp. 1-8.

Article Link (Online Journal): http://www.aascit.org/journal/ijabe

Funding Source:

Budget:

Total Budget (Tk.) :

Achievement/Findings:

Changes in SOC stocks are directly related to atmospheric C concentration. Agricultural management practices that increase SOC stocks thus may have profound effects on climate mitigation. Most agricultural soils in the study area contain below their potential level of SOC where triple cropped area contained extremely lower level. The highest organic carbon was found under agroforestry and the lowest organic carbon was found under fallow land. Organic carbon dynamics highly regulated by organic fertilizer application. Soil organic matter contents in farmlands have influenced by changes in land use intensity and soil management effects. Conventional tillage leads to significant increase of the soil organic matter content. Soil total nitrogen followed the similar results of soil organic carbon found higher in agroforestry system and lower in fallow land. Soil organic carbon contents decreased usually with increasing soil depth. Highest organic carbon found for 0-10 cm depth and lowest organic carbon found for 20-30 cm depth. C: N ratio found ranged from 4.9 to 11.6 and total nitrogen was strongly associated (R² = 0.98) with total organic carbon. This study showed clearly that land use change and land management have direct influence SOC and STN accumulation in soil. Therefore understanding and implementation of carbon and nitrogen balance in agriculture will help to maintain climate change mitigation and environmental protection from agriculture.

Knowledge Management: Journal