Available carbon and nitrate increase greenhouse gas emissions from soils affected by salinity

Soil Research ◽  
2017 ◽  
Vol 55 (1) ◽  
pp. 47 ◽  
Author(s):  
Duy Minh Dang ◽  
Ben Macdonald ◽  
Sören Warneke ◽  
Ian White

Sea-level rise and saline water intrusion have caused a shortage of fresh water and affected agricultural areas globally. Besides inundation, the salinity could alter soil nitrogen and carbon cycling in coastal soils. To examine the effect of salinity, an incubation experiment was used to investigate soil nitrogen and carbon cycling from an acid sulfate soil and an alluvial soil with and without additional nitrogen and carbon sources. Four levels of saline solution of 0.03, 10, 16 and 21dSm–1 were used to submerge acid sulfate and alluvial soil samples in a 125-mL jar. The experimental jars were incubated in the dark at 25°C. Gas samples were collected over 4 weeks and analysed for nitrous oxide (N2O), carbon dioxide (CO2) and methane (CH4). The results showed that salinity significantly decreased N2O emissions from the acid sulfate soil but did not affect emissions from the alluvial soil. Addition of glucose and nitrate enhanced N2O production in both salt-affected soils. Emissions of CO2 were not different among the salinity treatments, whereas available carbon and nitrate promoted soil respiration. Changes in CH4 fluxes over the 4-week incubation were the same for both soils, and substrate addition did not affect emissions in either soil. The findings indicate that salinity has altered carbon and nitrogen cycles in the acid sulfate soil, and future fertiliser and crop management will need to account for the changed nutrient cycling caused by saline water intrusion and climate change.

2016 ◽  
Vol 5 (3) ◽  
pp. 505 ◽  
Author(s):  
Rachmansyah Rachmansyah ◽  
Akhmad Mustafa ◽  
Mudian Paena

Kota Pekalongan memiliki lahan tambak yang produktivitas tambaknya masih tergolong relatif rendah. Oleh karena itu, dilakukan penelitian untuk mengetahui karakteristik lahan dalam upaya menentukan kesesuaian dan pengelolaan lahan untuk budidaya tambak demi peningkatan produktivitas tambak di Kota Pekalongan. Faktor yang dipertimbangkan dalam mengetahui karakteristik lahan adalah: tanah, topografi, hidrologi, vegetasi, dan iklim. Analisis spasial dalam Sistem Informasi Geografis digunakan dalam penentuan kesesuaian lahan untuk budidaya tambak. Pengelolaan lahan ditentukan berdasarkan karakteristik lahan yang disesuaikan dengan teknologi dan komoditas yang dapat diaplikasikan di tambak. Tanah tambak di Kota Pekalongan tergolong tanah aluvial non-sulfat masam yang tidak memiliki potensi kemasaman tanah yang tinggi dan sebagian kecil tanah sulfat masam. Sumber air laut untuk tambak tergolong agak keruh dan salinitas air tambak cukup bervariasi sebagai akibat adanya sumber air tawar yang berasal dari Sungai Pekalongan dan sodetan. Vegetasi bakau adalah jenis vegetasi yang dominan di kawasan tambak sebab adanya Program GERHAN (Gerakan Nasional Rehabilitasi Hutan dan Lahan) di Kota Pekalongan. Curah hujan di Kota Pekalongan sebesar 2.300 mm/tahun di mana curah hujan yang rendah dijumpai pada bulan Juli sampai Oktober. Di kawasan pesisir Kota Pekalongan dijumpai tambak, sawah, sawah terintrusi, dan pemukiman yang luasnya masing-masing 332,29; 372,53; 183,83; dan 619,73 ha. Dari luas tambak yang ada di Kota Pekalongan, yaitu 331,292 ha ternyata tidak ada tambak yang tergolong sangat sesuai (kelas S1), 191,856 ha tergolong cukup sesuai (kelas S2) dan 140,436 ha tergolong kurang sesuai (kelas S3). Pada areal yang mengandung unsur atau senyawa penyebab kemasaman yang tinggi disarankan untuk melakukan upaya perbaikan tanah terlebih dahulu berupa remediasi, pemberian pupuk yang mengandung nitrogen pada areal yang memiliki rasio C:N tanah yang tinggi serta pemberian pupuk kandang pada tanah yang mengandung liat lebih besar 60% dan bahan organik kurang dari 8%.Pekalongan City has brackishwater ponds with low productivity. Hence, a survey was conducted to know land characteristics as an effort to determine land suitability and land management to increase the productivity of brackishwater ponds in Pekalongan City, Central Java Province. Factors considered to determine the characteristics of land were soil, topography, hydrology, vegetation, and climate. Spatial analysis in Geographical Information System was used to determine land suitability for brackishwater ponds. Land management was determined based on the characteristics of land conditioned to the types of technology and commodity applied in the brackishwater ponds. Soil of brackishwater ponds in Pekalongan City was dominated by alluvial non-acid sulfate soil in large areas and acid sulfate soil in small areas. Source of sea water for brackishwater ponds has high turbidity and high variation of salinity due to presence of freshwater supply from Pekalongan River and man made canals. Mangrove vegetation is dominant in the coastal area of Pekalongan City, because the presence of GERHAN (National Action for Forest and Land Rehabilitation) Program. The average of rainfall in Pekalongan City is 2,230 mm/year, where low of rainfall occurrs in July until October. The result revealed that the coastal area of Pekalongan City had brackishwater ponds, paddy field, paddy field intruded saline water and settlement of 332.29 ha; 372.53 ha; 183.83ha; and 619.73 ha, respectively. From the total brackishwater ponds in Pekalongan City i.e. 331.292 ha, there were no brackishwater ponds classified as highly suitable (S1 class), but it was found moderately suitable or S2 class (191.856 ha) and marginally suitable or S3 class (140,436 ha). It is suggested to conduct improving soil quality first, including remediation of the areas that contain elements or compounds causing the high acidity of soil, fertilizing with fertilizer containing nitrogen in the areas that have high C:N ratio and applying manure in the soils that contain clay more than 60% and organic matter less than 8%. 


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