Enamul Haque

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.

Sunflower (Helianthus annuus L.) has recently been identified as a promising crop for the seasonally-fallow lands of the coastal region of the eastern Ganges delta; but its fertilizer requirement especially phosphorus (P) for higher yield has not yet been determined. The objectives of the experiment were to find out the optimum P rate which maximizes yield and P use efficiency with minimum positive P balance in soil. Accordingly an experiment was conducted in 2020, 2021 and 2023 using eight P rates having 0, 7.2, 14.4, 21.6, 28.8, 36.0, 43.2 and 50.4 kg P ha−1 in sunflower. The significantly higher achene yield over the years was found in 21.6 to 36.0 kg P ha−1, and 28.8 kg P ha−1 on a pooled yield basis and this rate had a minimum positive P balance (5.9 kg P ha−1). At 28.8 kg P ha−1, the partial factor productivity varied from 90 to 127, and agronomic efficiency of 22 to 49 kg achene kg−1 added P over the years. The P requirement in the coastal ecosystem was lower compared to inland agricultural soils. The 28.8 to 36 kg P ha−1 rate could be sufficient to meet P requirements of sunflower while maintaining P status in salt-affected coastal soils of the eastern Ganges delta.

On the one hand, the inherent intermittency in demands and renewable energy sources (RES) frequently bring challenges such as overload or surplus generation within microgrids. On the other hand, electric vehicle aggregations (EVAs) have garnered substantial attention as a pivotal strategy to address climate change and serve as a sustainable substitute for petroleum-based vehicles. However, the uncoordinated deployment of EVAs within microgrids, especially in the face of the intermittent nature of RES, poses a potential threat to the secure operation of microgrid systems. To tackle the mentioned issues, this research concentrates on interconnecting a group of scattered microgrids to create a multi-microgrid system. In more detail, by developing an energy management strategy to reconfigure the interconnections among microgrids, the efficient exchange of power among these multi-microgrid systems is facilitated, addressing the variability in load demands amidst the stochastic generation patterns of RESs. Besides, grid-to-vehicle (G2V) and vehicle-to-grid (V2G) concepts of EVAs are synchronized within the reconfigurable microgrid structure to enhance the flexibility of the model. To evaluate the model under realistic situations, a scenario-based method is also employed to reflect the effects of uncertainties on the model. The proposed approach, characterized by its mathematical convexity, allows for employing efficient solvers like CPLEX, ensuring the attainment of a feasible global solution within a finite timeframe. The effectiveness of the proposed method is demonstrated through its implementation on a modified 33-bus test system operated as multi-microgrid system. The results show the effectiveness of the proposed approach as a promising tool for optimizing the operation of reconfigurable multi-microgrid systems in the presence of EVAs, leading to operational cost reduction and voltage profile enhancement.

Conservation Agriculture (CA) is promoted as a novel practice for high yielding, rice-based crop rotations but there has been limited study of its effects on sulfur (S) balance. In an annual rice-rice-wheat cropping pattern, common in the Eastern Gangetic Plain (EGP), we evaluated S balance and crop productivity after 24 consecutive crops with minimum soil disturbance and increased crop residue retention treatments relative to conventional practice on a sulfur-deficient silt clay loam soil. The experiment was sampled after 8 continuous years (i.e., 24 crops) of (A) minimum soil disturbance (strip planting = SP) versus conventional tillage (CT) and (B) low crop residue retention (LR = current practice) or high residue retention (HR). Thereafter, during crops 25–30, the plots were split between the current recommended dose of S (CD) and 150% of CD (HD) to assess effects on partial S balance. Soils were re-sampled after crop 30. High residue retention and HD produced a positive S balance (9–10 kg ha− 1 yr− 1). The component crop yields and rice + rice + wheat yield were also significantly higher in HR with HD than other treatments. Soil organic carbon, total nitrogen and S content were significantly higher in SP coupled with HR. In both tillage systems, the current practice of LR with CD resulted in a small negative S balance (1–2 kg ha− 1 yr− 1). The intensive rice-rice-wheat cropping patterns of the EGP involve high grain yield and significant crop residue removal, but with CA there is an opportunity to reverse the current negative S balance and improve soil health while increasing crop yield.

The adoption of conservation agriculture (CA) practices is likely to alter soil phosphorus (P) pools and availability leading to changes in P fertilizer use and management. However, the impacts of CA practices on soil P fractions and their distribution in the soil profile under rice-based systems is not well-understood. This study examined the effect of two crop establishment practices (strip planting, SP and conventional tillage, CT) and two crop residue levels (high residue, HR- 40% of above ground biomass and low residue, LR- 15%) on P fractions in the soil profile under a lentil–mungbean–rice sequence. After three consecutive years of CA practice, covering nine crops, composite soil samples were collected at 0–5, 5–15, 15–30, 30–45 and 45–60 cm depths and analysed for solution P, NaHCO3-extracted inorganic (NaHCO3 Pi) and organic (NaHCO3Po) P, NaOH-extracted inorganic (NaOH Pi) and organic (NaOH Po) P, stable P, residue P, total P, soil organic carbon (SOC) and total nitrogen (N). The inorganic P (solution P, NaHCO3 Pi, NaOH Pi and stable P) comprised 53–59% while the organic P (NaHCO3 Po and NaOH Po) comprised only 6%–13% of total P. However, CA practices increased SOC with the corresponding increase in soil organic P fractions. HR increased solution P, NaOH Po, stable P, residue P, total P, as well as SOC contents along with the stocks of total carbon (C), N, and P at up to 15 cm while increasing NaHCO3 Pi, NaOH Pi and TN at up to 30 cm depth compared with the LR. Likewise, SP increased the inorganic P fractions (NaHCO3 Pi and NaOH Pi) at 0–30 cm depth over the CT while P fractions in the deeper soil layers were similar to each other. In conclusion, the increase in soil P pools at up to 15–30 cm depths especially because of increased crop residue retention should allow for a decrease in P fertilizer inputs in intensive rice-based systems.

Intensive rice-based systems are mining soil potassium (K) due to negative K balances. Conservation Agriculture (CA) practices may increase yield and economic return of rice-based systems but there is limited understanding of their effects on K pools and balances. This study evaluated crop productivity and K input–output balances under contrasting rice-based intensive cropping and long-term CA. The comprised three factors- (a) soil disturbance (strip planting, SP and conventional tillage, CT); (b) residue retention (low, LR, 20 cm by plant height and high, HR, 50 cm) and; (c) K application-100% K (recommended dose, RD), 50–75% K of RD (low dose, LD), and 125–150% K of RD (high dose, HD). The long-term experiment initiated in 2010 and soil samples were collected in 2018 after 24th crop and 2020 after 30th crop of triple cropping system. The K balances for the 2018 cropping cycle were negative, ranging from − 47 to − 82 kg ha−1 yr−1. In the 2020 cycle, when the high K dose was increased from 125 to 150% of RD, the negative K balance was significantly reduced in SP-HR-HD (− 19 kg ha−1 yr−1) while 23–35% higher cropping system yield was achieved. Leaching was a significant K loss pathway. Overall results indicate that minimum soil disturbance and increased crop residue retention had significant positive effects on cropping system yield and K balance. However, to achieve neutral K balance in intensive rice-based cropping systems, increased recycling of K from crop residue, higher doses of K addition or lower K losses are needed.

The availability and use efficiency of phosphorus (P) is low in the acidic Ganges delta floodplain soils. The aim of the present study was to increase the use efficiency of P by varying the methods and forms of P application. The experiment comprised a factorial combination of two methods (broadcasting and furrow placement) and two forms (granular and powder) with three rates of P fertilizer application (36, 48 and 60 kg P ha−1). Results showed that furrow placement of P application gave 10%–20% yield benefit over broadcasting method. Agronomic P use efficiency, partial factor productivity, economic efficiency and leaf P concentration were remarkably higher in furrow placement of P fertilizer than conventional broadcasting method. Numerically the application of powder form P fertilizer demonstrated higher yield compared to granular form of P application. The furrow placement of P fertilizer exhibited the higher yield at lower rate of P application (36–48 kg P ha−1) while opposite trends were observed for broadcasting. Thus, it is concluded that furrow placement of P fertilizer application at 36–48 kg ha−1would give the best grain yield of maize in the Ganges delta floodplain soils.

Cropping systems in the Ganges delta coastal region are being intensified by the insertion of new high-yielding crops, but nutrient requirements for these crops have not been determined. The objective of this study was to identify the yield limiting plant nutrients for growing monsoon rice and dry season maize under intensified cropping systems of the Ganges delta coastal floodplains. Using nutrient omission design, the treatments were as follows: full nutrient supply: nitrogen (N) + phosphorus (P) + potassium (K) + sulfur (S) + zinc (Zn) + boron (B); full nutrient minus N, P, K, S, Zn, or B; plus an unfertilized control. The treatments were tested in maize-early monsoon rice (Aus)-monsoon rice (Aman) crop sequence in 2018 and 2019 at south-central Ganges delta coastal region. Two additional single experiments were also conducted at southwestern site of the region with similar treatments. At south-central region, N omission reduced grain yield compared to full nutrients treatment by 60-71% in maize, 21-42% in early monsoon rice, and 13-21% in monsoon rice. Phosphorus omission reduced maize grain yield by 33-47%. In this region for maize, N and P were identified as serious yield limiting nutrients. By contrast, monsoon rice yields were mainly constrained by N omission. Tidal floodwater has potential to supply 3-38 kg mineral-N ha(-1) and 2-19 kg phosphate-P ha(-1) during monsoon which reduces the magnitude of response to nutrient omission in rice compared to maize. In south-western site, the N and P omission reduced grain yield by 22.6-56.1% and 12.7-14.6%, respectively, in rice. For intensify cropping rotations in the Ganges delta coastal floodplains, increased N and P fertilization is recommended, particularly for any dry land crops added to system.

In research settings in the Eastern Gangetic Plain, Conservation Agriculture (CA) reduces operational costs, including cost for machinery, labour and fuel, while increasing yields, profit and soil organic carbon. However, the impact of the CA practices when adopted by smallholder farms on their crop productivity and farm profitability in this region is not well understood. In three locations in Rajshahi and Thakurgaon districts, Bangladesh, where previous on-farm CA research and demonstrations had been focused, we assessed the adoption and impacts of CA technologies on 135 farms compared to 270 non-adopters. While the CA technology adoption is still ongoing in the study areas, those farmers who practiced CA technology decreased human labour by up to 34%, seed use by 31%, fertilisers by 6%, pesticides by 32%, and total cost of production up to 10% while cultivating lentil, mustard, maize and wheat. The respective increases in crop yield and net profit were up to 28% and 43%, respectively. Propensity score matching (PSM) methods further confirmed that CA technology adoption had significant impacts by increasing crop yield, reducing variable costs, and increasing adopters’ net income. Given the striking on-farm benefits of CA for smallholders in the EGP, programmes to expand the availability of minimum tillage planters, provide training to local service providers on CA methods, and the use of smart incentives should be evaluated to assist farmers to adopt CA seeding machinery and associated agronomic practices.

Intensive cropping in the Eastern Gangetic Plain has progressively depleted soil potassium (K) over time due to negative K balances. There is limited understanding of how alternative soil and crop management practices under Conservation Agriculture (CA) will alter the soil K pools in such soils. We hypothesized that long-term CA will reduce K depletion in soils through recycling and storing soil K. A split plot experiment with two factors-(A) soil disturbance (strip planting = SP and conventional = CT), and (B) residue retention (low, LR = 20 cm and high, HR = 50 cm) commenced in 2010 with three crops per annual cycle for 24 consecutive crops. Soil samples were then collected in December 2018 at 0-5, 5-15, 15-30, 30-45 and 45-60 cm to analyse fractions of K along with soil physical and chemical properties. All K fractions were higher in SP (by 300, 26, 7.8 and 2.4 mg kg(-1) for total, non-exchangeable, exchangeable and soil solution K, respectively) than in CT while HR was higher (by 267, 243, 18, 28.8 and 15.9 mg kg(-1) for total, mineral non-exchangeable, exchangeable and soil solution K, respectively) than in LR. While increased crop residue retention recycled more K to the soil which partly explains higher concentrations in K fractions, both increased residue retention and decreased soil disturbance increased SOC that can positively increase exchangeable K. Hence, the core components of CA, minimal soil disturbance and increased residue retention, resulted in larger K pools in soil and appear to be effective means for reversing negative K balances in these intensive rice-based cropping systems.