Soil Organic Matter in a West Bengal Inceptisol after 30 Years of Multiple Cropping and Fertilization

Abstract

Rice‐based multiple cropping systems are predominant in the Indo‐Gangetic Plains of Indian subcontinent. A decline in yield of such systems has been observed and ascribed to quantitative and qualitative variations of soil organic matter (SOM). We evaluated the impact of the annual rotation: rice (Oryza sativa L.), wheat (Triticum aestivum L.), jute (Corchorus olitorius L.), with and without fertilizer treatments (control, N, N–P, N–P–K, and N–P–K plus farmyard manure [FYM]) on SOM and aggregate properties. At 0‐ to 15‐cm soil depth, microbial biomass C and N, hot water–soluble C and N and hydrolyzable carbohydrates, and particulate organic matter C (POMC) and N (POMN) were found in the order N–P–K plus FYM > N–P–K > N–P > N > control. Over the course of the experiment, application of N alone decreased total organic C (TOC) by 20.4%, whereas N–P–K with or without FYM addition either maintained or enhanced compared to initial. Total soil N and mineralizable N declined in all the treatments except N–P–K plus FYM. Irrespective of treatments, microaggregates (53–250 μm) dominated with 43.9 to 51.3% of total soil aggregate size distribution, followed by macroaggregates (250–2000 μm with 34.6 to 40.1%). The C and N mineralization rate was greater in macroaggregates than in microaggregates, and correlated significantly with POMC (r = 0.67, P ≤ 0.01) and POMN (r = 0.88, P ≤ 0.01). Nitrogen–phosphorus–potassium plus FYM also improved overall soil aggregation as compared to other treatments. Therefore, the results suggest that the gradual depletion of nutrients and structural degradation may have collectively contributed to the crop yield declines in the rice–wheat–jute rotation and that the integrated use of N–P–K and FYM is an important nutrient management option for sustaining this cropping system.

Long term effects of fertilization on carbon and nitrogen sequestration and aggregate associated carbon and nitrogen in the Indian sub-Himalayas

“…Results from several other long-term Indian experiments also showed similar build up of total SOC due to application of manure with balanced fertilizers (Kanchikerimath and Singh 2001;Rudrappa et al 2005;Mandal et al 2007). Many studies reported that materials with a higher lignin content (FYM) result in a greater accumulation per unit of C input (Manna et al 2006). In contrast to our results, Manna et al (2006) observed decreased total SOC under imbalanced fertilizer application and unfertilized control.…”

“…Many studies reported that materials with a higher lignin content (FYM) result in a greater accumulation per unit of C input (Manna et al 2006). In contrast to our results, Manna et al (2006) observed decreased total SOC under imbalanced fertilizer application and unfertilized control. The gain in SOC concentration in the plots under unfertilized control was probably due to annual C addition from the biomass of both crops (Table 3) and higher humification rate of added SOM.…”

Effect of liming on the change of some agrochemical soil properties in a long-term fertilization experiment

“…This confirms that the method of fertilization helps to maintain or increase the soil organic carbon content under various habitat and agricultural conditions, which is seen from the results of long-term experiments carried out in Poland (Rutkowska et al 2004) and other countries of the world (Manna et al 2006).…”

Fertilization increases paddy soil organic carbon density

“…Compared to no fertilization, some studies suggested that SOC content increases under inorganic fertilization, especially for inorganic nitrogen (N) fertilizers (Majumder et al, 2007;Reid, 2008;Tong et al, 2009;Batlle-Bayer et al, 2010). López-Bellido et al (2010) and Luo et al (2010) suggested that the SOC content does not change, and others suggested that the SOC content decreases (Manna et al, 2006;Khan et al, 2007;Li and Zhang, 2007). Inorganic N fertilizers improve the crop residues in the soil, and thus improve the SOC.…”