Impacts of long-term tillage on carbon storage and crop yields

Abstract

In Brazil, the agricultural activities nowadays represent an important contribution for green house gases emissions (GEE), with 75% of carbon dioxide (CO2) and more than 90% of methane (CH4) and nitrous oxide (N2O). The main objective of the clean development mechanism (CDM) is to assist the developing countries to reach sustainable growth. These objectives may be reached through projects using biofuels to contribute to reduce GEE in developing countries. Amongst the biofuels, ethanol has been the most popular being produced already in large amounts both in Brazil and USA. Brazil has soil and climate adequate for the agricultural production of biofuel raw materials. Sugar cane is the main source of alcohol production because it already has a very well developed agricultural and industrial system. On the other hand, it is wise to consider the biofuel production potential from other sources of plants such as soybean, castor oil plant, maize, cassava, jatroba and sunflower. The rapid growth of sugar cane production in Brazil (357 Mt in 2003 to 425 Mt in 2006, and an estimation of 728 Mt in 2012) in addition to the legal restrictions to burn the sugar cane straw (which is being substituted by the mechanical harvesting) affects both the energy production as well as the GEE emissions from sugar cane. In this sense, it important to consider the carbon fixation potential for biofuel crops, mostly aiming at sustainable development and to maintain environmental quality. The effect of agricultural practices on GEE emissions is a headline subject, specially for CO2, the main component on green house effect resulting from human activities. Agricultural activities involving soil management, such as soil tillage, have a large effect on these emissions. The CO2 production inside the soil profile is related to the biological activity including root respiration and organic matter decomposition by microbes. Thus, the CO2 emission results from the production and transport processes for this gas inside the soil, which are strongly affected by soil moisture and temperature as well. In these way, the knowledge of the GEE emission dynamics in biofuel production systems involving long term experiments is very important in order to appropriately evaluate the GEE balance. The present project aims at quantifying the GEE in three experimental conditions: one long term (24 years) no tillage grain production, one 12 years long no tillage sugar cane production with mechanical harvesting without burning, and one 13 years long no tillage sugar cane production with manual harvesting after burning. All three experiments will have reference areas close by at which the GEE emissions will also be measured for comparison. (AU)