Soil Organic Carbon Thresholds and Nitrogen Management in Tropical Agroecosystems: Concepts and Prospects

Abstract

Soil organic carbon (SOC) is a potential soil fertility indicator for regulating nitrogen application in tropical farming systems. However, there are limited studies that have discussed SOC thresholds above or below which crop production could be diminished, or at which no or high response to nitrogen (N) application can be realized. This review explores the drivers of SOC concentration relevant for the establishment of thresholds. We further evaluate existing SOC thresholds for provoking no yield response or significant response to added N fertilizer. Key drivers for SOC concentration relevant in establishing thresholds are mainly climate, topography, texture, and land use management. Soil organic carbon threshold for sustaining soil quality is widely suggested to be about 2% below which deterioration may occur. For added N fertilizer management, specific SOC thresholds seem quite complex and are only valid after assuming other factors are non-limiting. In some soils, SOC levels as low as 0.5% result in fertilizer responses and soils as high as 2% SOC also respond to small N doses. Minimum SOC thresholds can be identified for a given soil type, but maximum thresholds depend on crop N requirements, crop N use efficiency and amount of N applied. However, there seem to exist critical total SOC ranges that could be targeted for optimal indigenous N supply and integrative soil functional benefits. These can be targeted as minimum levels in soil fertility restoration. In all, it is still difficult to establish a single minimum or maximum SOC threshold value that can be universally or regionally accepted.

Effects of enhancing soil organic carbon sequestration in the topsoil by fertilization on crop productivity and stability: Evidence from long-term experiments with wheat-maize cropping systems in China

“…Moreover there could be potential hazards of adding too much C to soils, such as surface crusting, increased detachment by raindrops, decreased hydraulic conductivity (Haynes and Naidu, 1998) and water-repellency (Olsen et al, 1970). Addition of excessive amounts organic materials to soils could also lead to losses in soil nitrogen (N) and/ or phosphorus (P), resulting in surface and ground-water pollution (Patrick et al, 2013).…”

Using DSSAT-CENTURY Model to Simulate Soil Organic Carbon Dynamics Under a Low-Input Maize Cropping System

“…Soil Organic Carbon (SOC) is a key soil fertility indicator in heterogeneous tropical farming systems in Sub-Saharan Africa (Woomer, Martin, Albretch, Resck, & Scharpenseel, 1994;Musinguzi et al, 2013). Maintenance of high SOC has benefits such as increased cation exchange capacity, moisture storage and mineralizable nutrients; improved soil structure and aggregate stability (Reeves, 1997;Karlen, Andrews, & Doran, 2001).…”

Organic Carbon Stocks, Dynamics and Restoration in Relation to Soils of Agroecosystems in Ethiopia: A Review

“…Management of agroecosystems is an important approach to restore SOC pools. SOC storage is a universal indicator to assess the status and improvement of land management and soil fertility (Lal, 2007;Patrick et al, 2013). It has been addressed through improvement of degraded agroecosystems, enhancement of organic carbon pool and assisting soil quality (Lal, 2011).…”