Typology of rice-based cropping systems for improved soil carbon management: Capturing smallholder farming opportunities and constraints in Dinajpur, Bangladesh

Abstract

Characterization of smallholder land resource endowment and cropping practice can assist in the implementation of a more tailored approach to Soil Carbon Management (SCM). Land resource and cropping practice data, stratified by soil physiography, was collected through a survey involving 83 farmers in four upazila of Dinajpur district, Bangladesh. The aim was to determine a farming system typology based on smallholder land resource endowment and cropping practices, and to consider the likelihood of soil carbon improvement under the typology. A Cluster Analysis was performed using data on seven variables that combined land resource (physiography, land type, landholding, farm size) and cropping practice (cropping system, cropping intensity, crop rotation) characteristics to determine a farming system typology. The resulting typology, referred to as Soil Carbon Improvement Likelihood (SCIL), identified three different farming system types. These were then assessed with regard to their potential for improving soil carbon in these systems. The most prevalent SCIL, Medium SCIL (Type 1, 42%) consists of the maize-rice, wheat-rice and veg.-rice cropping systems in the HL areas of the Piedmont plain, Floodplain and Terrace. It is managed with high fertilization, low crop rotation and low to medium crop residue retention. The next most prevalent SCIL, Low SCIL (Type 3, 30%) consists of a rice-rice cropping system in the HL and MHL areas of the Piedmont plain, Floodplain and Terrace, and is managed with medium fertilization, no crop rotation and limited residue retention. The least prevalent farming system type, the High SCIL (Type 2, 28%) consists of crop-diversified and mustard-rice cropping systems in the MHL areas of the Floodplain and Terrace, which is managed with high fertilization, crop rotation and high crop residue retention. This study showed that cropping systems with higher crop intensification and high retention of crop residue, on the Floodplain soil physiography and MHL land inundation type, provide the greatest opportunity for improved SCM, but were represented by less than one-third of the farmers (n = 20) in this survey. These farmers were also mainly private landholders. The typology presented here can potentially serve as a practical framework for delineating cropping systems and management under particular land resource settings to undertake more targeted innovations and SCM priorities in Rice-based Cropping Systems.