Greenhouse gas emission and soil carbon stock as efected by soil acidity amelioration and management system

Author(s)

Moniki Campos Janegitz

• Document type: Doctoral Thesis
• Press: Botucatu. 2016-04-07.
• Institution: Universidade Estadual Paulista (Unesp). Faculdade de Ciências Agronômicas. Botucatu
• Defense date: 2016-02-12
• Advisor: Ciro Antonio Rosolem

Abstract

Economically viable options to mitigate emissions of greenhouse gases include increasing the stocks of croplands. The use of liming acid soils is essential to correct soil acidity and contributes to high production resulting in carbon emission in the atmosphere. The use of lime or silicate application with gypsum may improve the balance of soil carbon through increased root growth compared to the use of lime only. The main objective of this work is to study changes in the carbon storage in the soil profile as well as changes in carbon emission affected by soil acidity amelioration. The experiment was carried out in an Oxisol in Botucatu, São Paulo at the Lageado Experimental Farm under no tillage and another in a conventional system area. Crop cultivation was soybean in the summer and corn+Urucloa in the winter in the first year, and millet+Urocloa in second year cultivation. The experimental design was a randomized block with five treatments and four replications. The treatments were: control, lime, silicate, gypsum+ lime and gypsum+ silicate. Deformed and under formed soil samples of both experimental areas were taken at a depth of one meter before treatment applications and in soybean sown in November. In the first year, soil samples were collected at depths from 0 to 0.6 m. Soil fertility, carbon content, organic matter physical fractionation and bulk density were evaluated. Contribution and the persistence of the amount of straw produced in each crop and input of carbon was also evaluated. Leaf analysis, root quantification, grain yield and carbon content in the grains and roots were also analyzed. CO2, CH4 and N2O fluxes were determined from the soil using static chambers and were measured after the treatment applications, soybean planting in the summer and winter crops, in March 2013 and 2014 under corn+Urochloa and millet+Urochloa. Gas fluxes were measured for 22 months, totaling 80 sampling periods. We evaluated the CO2-C/[residue- C+soil-C]; the carbon emission quotient was proposed as C retention index (CRI), in which low values indicate a high capacity of the management system to store C in the soil. According to the IPCC in CO2- equivalent factors, nitrogen oxide and the methane emission should be adjusted. The annual average emission was 7,8 Mg ha-1of C-CO2- equivalent. Soil amendments were equally efficient in soil acidity amelioration. Cultivation systems influenced the soil fertility, carbon stock, carbon fractions in soil and greenhouse gases. Conservation systems, such as no till, contributed to the improvement of the soil-plant environment compared to the conventional system. The lime use associated or not with gypsum increased the initial CO2 emission, while N2O emission was decreased in the presence of silicate. For CH4 inflow into the ground, no difference between treatments was observed after 35 days of treatment applications, with no plants in the soil. However, we concluded that soil acidity amelioration did not increase the C-CO2 equivalent emission from biosphere to atmosphere compared to the treatment control after 22 months of trial. Data on lime-contributed to atmospheric CO2 and the effect stabilized over time. Limed treatments increased soil organic carbon confirming priming effect of liming. Accumulated C-CO2 emission was similar by the both soil management systems. It is not possible to analyze the soil tillage system with a study on greenhouse gas emissions only. Regarding adopting no-till, it is still the main conservation management practice having direct effects on the carbon mitigation in the system. Chemical soil characteristics were influenced with gypsum use as soil carbon stock and soybean yields also increased with this treatment. (AU)

• FAPESP's process: 12/09550-0 - Green house gas emissions as affected by soil management and acidity amelioration
• Grantee: Moniki Campos Janegitz
• Support Opportunities: Scholarships in Brazil - Doctorate