Organic Amendments Influence Soil Organic Carbon Pools and Rice–Wheat Productivity

Abstract

Soil organic C (SOC) pools under long‐term management practices provide information on C sequestration pathways, soil quality maintenance, and crop productivity. Farmyard manure (FYM), paddy straw (PS), and green manure (GM) along with inorganic fertilizers were used in a 19‐yr‐old rice (Oryza sativa L.)–wheat (Triticum aestivum L.) cropping system in subtropical India to evaluate their impact on SOC stock, its different pools—total organic C (Ctot); oxidizable organic C (Coc) and its four fractions of very labile (Cfrac1), labile (Cfrac2), less labile (Cfrac3), and nonlabile C (Cfrac4); microbial biomass C (Cmic); and mineralizable C (Cmin). Cropping with only N–P–K fertilization just maintained SOC content, while N–P–K plus organics increased SOC by 24.3% over the control, their relative efficacy being FYM > PS > GM. A minimum of 3.56 Mg C ha−1 yr−1 was required to be added as organic amendments to compensate for SOC loss from cropping. The passive (Cfrac3 + Cfrac4) pool and Cmin constituted about 39 and 11.5%, respectively, of Ctot Organics contributed toward the passive pool in the order FYM > PS > GM. Most of the pools were significantly (P = 0.005) correlated with each other. Yield and sustainable yield index were strongly related with Cfrac1, Coc, Cmic, and Cmin Results suggest Cfrac1 as a useful indicator for assessing soil health, and balanced fertilization with FYM as suitable management for sustaining crop productivity of the rice–wheat system.

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

“…The range of sequestration efficiencies was similar to that observed from the Indian humid subtropical plains at 20-cm depth under a rice-wheat over 20-30 years (7.6-14%, Majumder et al, 2008) and a rice-lentil (Lens culinaris) system (9.9%, Srinivasarao et al, 2012), but lower than that from the temperate region of North America (14-21%, Rasmussen and Collins, 1991) and higher than that from topsoil of subtropical regions under a rice-wheat-jute (Corchorus olotorius L.) system (4-5%, Majumder et al, 2007).…”

CO<sub>2</sub> emission and structural characteristics of two calcareous soils amended with municipal solid waste and plant residue

“…In addition, the C : N ratio for AR-treated soils was greater than that for the MSW-treated soils (Table 2). In general, a higher ratio of C : N can be associated with a lower decomposition rate of organic sources (Majumder et al, 2008).…”

“…It is well known that the microbial decomposition processes are controlled by the substrate quality (e.g., lignin and polyphenol content) and the availability of labile carbon (Koranda et al, 2013;Smith et al, 2015). In some studies, the C : N ratio has been attributed to the rate of decomposability of organic inputs; i.e., the lower ratio can be associated with the higher rate of carbon mineralization and CO 2 emission (Majumder et al, 2008). It can be assumed that compared to MSW, the application of AR with less easily degradable components may cause the formation of more stable soil organic complexes, resulting in more resistance against the microbial decomposition (Majumder et al, 2008;Mahmoodabadi and Heydarpour, 2014).…”

“…In some studies, the C : N ratio has been attributed to the rate of decomposability of organic inputs; i.e., the lower ratio can be associated with the higher rate of carbon mineralization and CO 2 emission (Majumder et al, 2008). It can be assumed that compared to MSW, the application of AR with less easily degradable components may cause the formation of more stable soil organic complexes, resulting in more resistance against the microbial decomposition (Majumder et al, 2008;Mahmoodabadi and Heydarpour, 2014). Therefore, AR shows slower microbial decomposition as well as a lower mineralization rate (Liu et al, 2010;Cely et al, 2014).…”

Soil organic carbon and microbial community structure exhibit different responses to three land use types in the North China Plain

“…The labile fractions of the SOC pool are more sensitive to changes in agricultural management practices than is the total SOC (Haynes 2005). These pools can be fractionated by physical, chemical, or biological techniques as indicators of soil quality (Weil et al 2003;Majumder et al 2008;Imaz et al 2010). However, few studies have investigated how SOC pools respond to different agricultural land use types in reclaimed soils (Tian et al 2012).…”