A 25-year record of carbon sequestration and soil properties in intensive agriculture

Abstract

-As a major carbon pool on earth, soil organic carbon may act either as a sink or a source of atmospheric CO 2 , a greenhouse gas. Soil organic carbon is also impacting fertility, and, in turn, crop yields. However, knowledge of the impact of cropping techniques on the long-term behavior of soil carbon is scarce. Several studies have shown that continuous cropping decreases soil organic carbon stocks, rapidly in the initial years then at a slower rate, approaching a new equilibrium after 30 to 50 years. For instance, a study of intensive corn cropping for 35 years on temperate soils showed a 50% decrease in soil organic carbon. Our study is located in the North Indian state of Punjab. It is the most intensively cultivated region in the country with a cropping intensity of 190%, predominantly of a rice-wheat system. Due to high nutrient demand and its continuous cultivation, the cropping system is presumed to adversely affect soil organic carbon and other soil properties. However, this has been postulated without any real-time data analysis on a regional scale. Therefore, we evaluated soil data for 25 years from 1981/82 to 2005/06 to investigate the impact of intensive agriculture on C sequestration and soil properties on a regional scale. The results showed that, unexpectedly, intensive agriculture has resulted in improved soil organic carbon (SOC) status. As a weighted average for the whole state, SOC increased from 2.9 g kg −1 in 1981/82 to 4.0 g kg −1 in 2005/06, an increase of 38%. Increased productivity of rice and wheat resulted in enhanced C sequestration in the plough layer by 0.8 t C ha −1 per ton of increased grain production. Soil pH declined by 0.8 pH units from 8.5 in 1981/82 to 7.7 in 2005/06. This pH decline has positive implications for availability of phosphorus and micronutrients such as Zn, Fe and Mn. Changes in plant-available P in soil were related to the amount of fertilizer P applied. The status of available P in soils increased from 19.9 kg ha −1 in 1981/82 to 29.2 kg P ha −1 during 2005/06. The status of plant-available K in soil remained almost unaltered and averaged 106 and 123 mg kg −1 soil in 1981/82 and 2005/06, respectively. The analysis showed that intensive cultivation of a rice-wheat system unexpectedly resulted in improved C sequestration, a favorable pH environment and amelioration of the soil salinity.carbon sequestration / soil quality / soil pH / available nutrient status / intensive agriculture / rice-wheat sustainability / yield

Agricultural carbon flux changes driven by intensive plastic greenhouse cultivation in five climatic regions of China

“…4) after the conversion. The average soil carbon sequestration rate following the conversion from CVC to PGVC is about six times greater than that of the conversion from conventional cropland to no-till (in China, 0.16e0.39 Mg C ha À1 yr À1 , Lu et al, 2009 and in USA, 0.34 Mg C ha À1 yr À1 , West and Marland, 2002;respectively), and about 3.5-fold greater than that of rice-wheat intensive agriculture (0.62 Mg C ha À1 yr À1 , Benbi and Brar, 2009). This may be primarily attributed to the higher organic fertilizer carbon inputs (1.3-to 3.0-fold that of CVC, Fig.…”

“…4). This is attributed to greater carbon input through root exudates and organic fertilizer input in the colder regions (Benbi and Brar, 2009;Qiu et al, 2010;Wang et al, 2011). The PGVC in colder regions received more organic fertilizers than that in warmer regions because of a greater economic return from PGVC in colder regions.…”

Soil carbon sequestration: an innovative strategy for reducing atmospheric carbon dioxide concentration

“…Furthermore, SCS is natural, cost-effective and environmental friendly process and it is also helpful to achieve food security by improving soil fertility (Lal 2004a). Literature provides ample evidence on the mechanisms and processes of C-sequestration especially in soils (Kögel-Knabner et al 2008;Lal 2009;Benbi and Brar 2009;Sigua and Coleman 2009;Jones et al 2009;Morra et al 2010). However, the present review was aimed to critically analyze SCS as a carbon mitigation option and its role in agricultural productivity, wasteland reclamation, increment in biological diversity and its future perspectives.…”

Soil carbon pools under poplar-based agroforestry, rice-wheat, and maize-wheat cropping systems in semi-arid India

“…There are reports of stagnating or declining rice and wheat yields in the IGP (Ladha et al 2003), which have presumably been related to declining soil organic matter (SOM) content and decreased soil fertility (Bhandari et al 2002;Regmi et al 2002). However, temporal analysis of 25-years data on organic C content of the regional soils showed that the stagnating productivity was not related to SOC (Benbi and Brar 2009). So far there is no information available on the quality of SOM under ricewheat system in comparison to other agroecosystems.…”