The extent to which Conservation Agriculture (CA) practices alter nitrogen (N) balance in intensive rice-based cropping systems of the Eastern Indo-Gangetic Plain was examined, focusing on a legume dominated-system (LDS) and a cereal dominated-system (CDS) in north-west Bangladesh. Three crop establishment methods were imposed—strip planting (SP) and bed planting (BP) for non rice crops with non-puddled rice establishment; compared with conventional tillage (CT) for non rice crops along with puddled transplanting of rice. Two levels of crop residue retention were superimposed—high (HR) and low (LR - conventional farm practice) crop residue retention. The CA practices (SP and non-puddled rice with HR) increased total soil N concentrations, and the soil N-stocks at 0–0.075 m over CT and LR in both CDS and LDS sites after 2.5 years. At 0–0.15 m soil depth, total soil N concentrations increased over time under SP and BP, but decreased with CT. In LDS, annual soil N increase (65 kg N ha⁻¹) occurred with SP while negligible N losses were observed under CT at both levels of residue retention at 0–0.15 m soil depth. The N accumulation rate under HR was 24.5 kg N ha⁻¹ higher than LR. The N balance calculation over 2.5 years indicated an estimated soil N gain (8–11%) in SPHR and SPLR but a loss in CT. In CDS, neither treatments accumulated soil N but N losses were greater in CT. The effect of crop establishment methods on soil NH₄-N and NO₃-N at the early growth stage of cool dry season cropping was small and inconsistent. However, SP with HR maintained higher overall crop and system N uptake compared to CT and LR. Thus, CA practices altered the N balance which slowed the decline in soil N-stocks in the cereal-dominated rotation while resulting in a positive N balance in the legume-dominated rotation.

The tillage method determines several soil physical parameters that affect the emergence of post-rice chickpea (Cicer arietinum L.) in the Indo-Gangetic Plain of South Asia. Mechanised row-sowing with minimum soil disturbance and crop residue retention in medium-to-heavy-textured soils will alter the seedbed when compared to that prepared after traditional full tillage and broadcast sowing. Whilst minimum soil disturbance and timely sowing may alleviate the soil water constraint to crop establishment, other soil physical properties such as soil strength, bulk density, and aggregate size may still inhibit seedling emergence and root elongation. This study’s objective was to determine the limitations to chickpea crop establishment with increasing bulk density and soil strength, and different aggregate sizes below and above the seed. In two growth cabinet studies, chickpea seed was sown in clay soil with (i) a bulk density range of 1.3–1.9 Mg m⁻³ (Experiment 1) and (ii) the combination of bulk densities (1.3 and 1.8 Mg m⁻³) and aggregate sizes (4 mm) above and below the seed (Experiment 2). Root length was significantly reduced with increasing bulk density (>1.4 Mg m⁻³), and soil strength impeded early root growth at >1 MPa. Where main root growth was impeded due to high bulk density and soil strength, a greater proportion of total root growth was associated with the elongation of lateral roots. The present study suggests that the soil above the seed needs to be loosely compacted (<1.3 Mg m⁻³) for seedling emergence to occur. Further research is needed to determine the size of the soil aggregates, which optimise germination and emergence. We conclude that soil strength values typical of field conditions in the Indo-Gangetic Plain at sowing will impede the root growth of chickpea seedlings. This effect can be minimised by changing tillage operations to produce seedbed conditions that are within the limiting thresholds of bulk density and soil strength.