• Energy Research

Plant growth regulators are naturally biosynthesized chemicals in plants that influence physiological processes. Their synthetic analogous trigger numerous biochemical and physiological processes involved in the growth and development of plants. Nowadays, due to changing climatic scenario, numerous biotic and abiotic stresses hamper seed germination, seedling growth, and plant development leading to a decline in biological and economic yields. However, plant growth regulators (PGRs) can potentially play a fundamental role in regulating plant responses to various abiotic stresses and hence, contribute to plant adaptation under adverse environments. The major effects of abiotic stresses are growth and yield disturbance, and both these effects are directly overseen by the PGRs. Different types of PGRs such as abscisic acid (ABA), salicylic acid (SA), ethylene (ET), and jasmonates (JAs) are connected to boosting the response of plants to multiple stresses. In contrast, PGRs including cytokinins (CKs), gibberellins (GAs), auxin, and relatively novel PGRs such as strigolactones (SLs), and brassinosteroids (BRs) are involved in plant growth and development under normal and stressful environmental conditions. Besides, polyamines and nitric oxide (NO), although not considered as phytohormones, have been included in the current review due to their involvement in the regulation of several plant processes and stress responses. These PGRs are crucial for regulating stress adaptation through the modulates physiological, biochemical, and molecular processes and activation of the defense system, upregulating of transcript levels, transcription factors, metabolism genes, and stress proteins at cellular levels. The current review presents an acumen of the recent progress made on different PGRs to improve plant tolerance to abiotic stress such as heat, drought, salinity, and flood. Moreover, it highlights the research gaps on underlying mechanisms of PGRs biosynthesis under stressed conditions and their potential roles in imparting tolerance against adverse effects of suboptimal growth conditions.

Rationale: Greenhouse gas (GHG) emissions from crop agriculture are of great concern in the context of changing climatic conditions; however, in most cases, data based on lifecycle assessments are not available for grain yield variations or the carbon footprint of maize. The current study aimed to determine net carbon emissions and sequestration for maize grown in Bangladesh. Methods: The static closed-chamber technique was used to determine total GHG emissions using data on GHG emissions from maize fields and secondary sources for inputs. A secondary source for regional yield data was used in the current study. GHG emission intensity is defined as the ratio of total emissions to grain yield. The net GHG emission/carbon sequestration was determined by subtracting total GHG emissions (CO2 eq.) from net primary production (NPP). Results: Grain yields varied from 1590 to 9300 kg ha−1 in the wet season and from 680 to 11,820 kg ha−1 in the dry season. GHG emission intensities were 0.53–2.21 and 0.37–1.70 kg CO2 eq. kg−1 grain in the wet and dry seasons, respectively. In Bangladesh, the total estimated GHG emissions were 1.66–4.09 million tonnes (MT) CO2 eq. from 2015 to 2020, whereas the net total CO2 sequestration was 1.51–3.91 MT. The net CO2 sequestration rates were 984.3–5757.4 kg ha−1 in the wet season and 1188.62–5757.39 kg ha−1 in the dry season. This study observed spatial variations in carbon emissions and sequestration depending on growing seasons. In the rice–maize pattern, maize sequestered about 1.23 MT CO2 eq. per year−1, but rice emitted about 0.16 MT CO2 eq. per year−1. This study showed potential spatiotemporal variations in carbon footprints. Recommendation: Special care is needed to improve maize grain yields in the wet season. Fertiliser and water use efficiencies need to be improved to minimise GHG emissions under changing climatic conditions. Efforts to increase the area under cultivation with rice–maize or other non-rice crop-based cropping systems are needed to augment CO2 sequestration. The generation of a regional data bank on carbon footprints would be beneficial for combating the impact of climate change.

AbstractThe integrated farming system (IFS) is a holistic farming approach specially designed for small/marginal farmers to enhance the system productivity, profitability, and employment generation of their farm, ultimately ensuring their food and nutrition security for their livelihood. The mechanism of IFS offers various ecosystem services making farms environment‐friendly, sustainable, and climate‐resilient. IFS is characterized by the allocation of different agricultural components systematically in a single farm performing synergistically among themselves making the farm more productive, healthy, biodiversity enriched, and eco‐friendly than simplified farms. Therefore, this review paper represents an extensive analysis of existing literature on IFS exploring its concept, components, and need, and emphasizing its potential for higher system productivity, profitability, and employment generation in a sustainable manner. Moreover, it develops a conceptualization of the relationship among different agricultural components in a single farm exploring its role in ecosystem services (reducing greenhouse gases, carbon sequestration, nutrient recycling, improving soil health, and biodiversity conservation).

Determination of the optimum sowing window not only can improve maize yield significantly but also can fit maize in the existing cropping pattern. To get the advantages of sowing maize at the optimum time, a study was designed and carried out at the research field of Bangladesh Agricultural Research Institute, Rangpur, Bangladesh during 2015–2017. Another aim of the study was to forecast the yield of maize for the northern and western regions of Bangladesh using the CERES-Maize model. The study considered 5 November, 20 November, 5 December, 20 December, and 5 January as sowing dates for maize to identify the optimum sowing window. Three hybrid maize varieties, viz., BARI Hybrid Maize-9 (BHM-9), NK-40, and Pioneer30V92 were used. The study was laid out in a split-plot design, assigning the sowing dates in the main plot and the varieties in the sub-plot. To forecast the yield, the daily weather data of 2017 were subjected to run the model along with thirty years (1986–2015) of weather data. The genetic coefficients of the tested maize varieties were obtained through calibration of the model by using the observed field data of 2015–2016 and through validation by using the data of 2016–2017. The seasonal analysis was done using the DSSAT CERES-Maize model to confirm the experimental findings for optimizing the sowing window for maize at the northern region (Rangpur) of the country and subsequently adjusted the model for the western region (Jashore). The model performances were satisfactory for crop phenology, biomass, and grain yield. The NRMSE for anthesis was 0.66% to 1.39%, 0.67% to 0.89% for maturity date, 1.78% to 3.89% for grain yield, and 1.73% to 3.17% for biomass yield. The optimum sowing window for maize at the Rangpur region was 5 November to 5 December and 5 to 20 November for the Jashore region. The CERES-Maize model was promising for yield forecasting of the tested maize varieties. It gave a realistic yield forecast at approximately 45 days prior to the harvest of all the tested varieties. The study results are expected to be useful for both the farmers and the policy planners to meet up the future maize demands.

Water scarceness is a major threat to wheat productivity under changing climate scenarios, especially in arid and semi-arid regions. However, growing drought-tolerant wheat genotypes could be a sustainable option to enhance wheat productivity under drought stress conditions. The aim of this study was to evaluate the effect of mild to severe drought stress on gas exchange parameters, relative water content, SPAD-chlorophyll value, and yield-related parameters of 14 wheat genotypes being cultivated in arid to semi-arid areas on large scale. The genotypes were grown in earthen pots under three drought levels, namely (1) control-well watered, (2) mild water stress, i.e., 60% water holding capacity, and (3) severe water stress, i.e., 40% water holding capacity. The drought was imposed from the jointing stage to physiological maturity. Drought significantly decreased net photosynthesis, stomatal conductance, relative water contents, 100-grain weight, and grain yield in all genotypes. However, the reduction percentage was different in different genotypes under drought stress compared with well-watered conditions. The highest relative water content (65.2%) was maintained by the genotype Galaxy-2013, followed by AAS-2011 (64.6%) and Johar-2016 (62.3%) under severe drought conditions. Likewise, Galaxy-2013 showed the highest net photosynthesis and stomatal conductance under severe drought conditions. The highest grain yield per plant (6.2 g) and 100-grain weight (3.3 g) was also recorded in Galaxy-2013 under severe drought conditions, while the highest grain yield under well-watered conditions was recorded in Johar-2016, followed by Galaxy-2013. These results suggest that wheat variety Galaxy-2013 could be cultivated extensively to obtain good wheat yield under limited water conditions.

In semi-arid tropics, sugarcane yield and quality are affected by deficiencies in soil nutrients, including potassium and calcium. We examined the effects of two different potassium fertilizers, a traditional muriate of potash (MOP) and polyhalite (which contains potassium and calcium), on sugarcane growth, yield, and quality. Experimental treatments compared a control 0 kg K ha−1 (T1) to potassium applied as MOP only at 80 kg K ha−1 (T2) and at 120 kg K ha−1 (T3), and potassium applied as an equal split of MOP and polyhalite at 80 kg K ha−1 (T4) and at 120 kg K ha−1 (T5). Relative to the control the potassium-enhanced treatments had improved rates of key growth parameters, and of cane yields, which were 4.4, 6.2, 8.2, and 9.9% higher in T2, T3, T4,, and T5, respectively, than in T1. Regardless of fertilizer used, potassium applied at 80 kg K ha−1 achieved the highest sugar purity and commercial cane sugar content. All potassium fertilizer treatments had reduced (although non-significant) incidences of three key sugarcane insect pests. The economic benefits of polyhalite were reduced due to its higher cost relative to MOP. Combining MOP and polyhalite equally to achieve an application rate of 80 kg K ha−1 is recommended to enhance sugarcane growth and yield.

Facing cold stress is amajor constraint in seedling production during the winter season as, most particularly in recent times due to uncertain climatic conditions, no sustainable technology has been reported that could be easily adopted by farmers withlimited resources. Therefore, field experiments were carried out during winter 2017–2018 and 2018–2019 at the Central Research Farm of Bidhan Chandra KrishiViswavidyalaya, West Bengal, India to study the growth, survival potential, yield and nutritional and biochemical properties of boro rice seedlings as influenced by two seedbed management practices viz. conventional seedbed (farmers’ practice) and improved seedbed (polythene protected with micronutrient supplementation). The major objective was to lower the nurserybed duration without compromising seedlings’ health and to studythe economic viability during the winter season. The experiment was laid out in ten experimental units and deployed anindependent-sample t-test to compare the performance of the seedlings. The microclimatic changes were also itemized from both seedbeds. The seeds sownunder improved nursery conditions resulted in better seedling emergence (~90%) and survival percentage (~85%) as compared to the conventional seedbed (~70% and 65%). Growth attributes in terms of plant height, biomass accumulation, root characteristics, tiller count, and growth rate were observed to be better from the polythene-protected nursery bed. Theimproved nursery bed accounted for 20% higher seedling count at the time of transplantation over the conventional bed. The microclimatic situation under a polythene covering was also favorable for germination and seedling growth. Maximum nutrient (N, P, and K) concentrations, as well as chlorophyll content, wererecorded from improved seedlings. Results suggested that the improved seedbed management was apotential alternative toearly embolden seedling production during the winter to avoid climatic abnormalities. Most importantly, improved seedbeds ensured a comprehensive route from germination to healthy seedling production without any failure in thesmalltime window, which involvedless input as well as cost involvement. This technique could diffusethe problem oflate sowing conditions in the rice–rice cropping system.