Effect of Elevated Air Temperature and Carbon Dioxide Levels on Dry Season Irrigated Rice Productivity in Bangladesh

Agricultural productivity is affected by air temperature and CO2 concentration. The relationships among grain yields of dry season irrigated rice (Boro) varieties (BRRI dhan28, BRRI dhan29 and BRRI dhan58) with increased temperatures and CO2 concentrations were investigated for futuristic crop management in six regions of Bangladesh using CERES-Rice model (DSSATv4.6). Maximum and minimum temperature increase rates considered were 0°C, +1°C, +2°C, +3°C and +4°C and CO2 concentrations were ambient (380), 421, 538, 670 and 936 ppm. At ambient temperature and CO2 concentration, attainable grain yields varied from 6506 to 8076 kg·ha-1 depending on rice varieties. In general, grain yield reduction would be the highest (13% - 23%) if temperature rises by 4°C and growth duration reduction would be 23 - 33 days. Grain yield reductions with 1°C, 2°C and 3°C rise in temperature are likely to be compensated by increased CO2 levels of 421, 538 and 670 ppm, respectively. In future, the highest reduction in grain yield and growth duration would be in cooler region and the least in warmer saline region of the country. Appropriate adaptive techniques like shifting in planting dates, water and nitrogen fertilizer management would be needed to overcome climate change impacts on rice production.

Rice Transplanting Mechanization in Bangladesh: Way to Make It Sustainable

“Rice transplanter” has brought a radical change in the method of rice seedlings transplanting in Bangladesh. The machine is gaining popularity with the increase of labor crisis during the peak period of transplanting, reduction time of in-between crops, rapid urbanization and industrialization, and changing socio-economic status of the farmers. Alternatively, the traditional way of rice transplanting is labor-intensive and involves high drudgery. Mechanical rice transplanter is cost-effective and operation-friendly. It is suitable to plant young seedlings maintaining plant to plant and line to line distance which plays an important role in increasing yield. Moreover, it is easy to take care of the crops planted in rows. It helps in maintaining soil physical properties and is considered to be better from a crop management and productivity point of view. In malignancy of having an edge over the traditional broadcasting, the adoption rate of mechanical transplanters is low due to high primary investment, lack of knowledge in growing mat type nursery, lack of repair and maintenance facility to the end-users, and unavailability of spare parts. Imparting these, available supply, entrepreneurship development, and encouraging custom hire services may be some of the practical results for adding the rice area under mechanical transplanting. This review summarizes the problems and prospects associated with seedling rice transplanting, technological gaps in the adoption of mechanical transplanters in a sustainable manner, and future ways to make transplanters more user-friendly and cost-effective.

Effect of Seeding Density on Mat-Type Seedling Quality for Mechanical Transplanting in Dry Season Rice

Rice transplanting with a transplanter is a cost-effective process. Due to labor shortages during the peak time of rice transplanting, it is a promising technology in Bangladesh. However, the high-quality mat-type seedling is a prerequisite factor for mechanical transplanting. The experiments were conducted at three different locations (Gazipur, Tangail, and Rangpur) during the dry season (Boro)/2019-20 to determine the best seeding density for high-quality mat-type seedlings to be prepared for mechanical rice transplanters. The effects of seeding rate on seedling quality such as survival rate, seedling strength, stem thickness of newly released boro rice varieties BRRI dhan86, BRRI dhan89, and BRRI dhan92 were studied using four seeding rates (130, 140, 150, 160 g/tray). Results revealed that BRRI dhan92 showed quick seedling emergence compared to BRRI dhan89 and BRRI dhan86. Seedling mortality was found the lowest BRRI dhan92 while the highest in BRRI dhan86. 25 - 30 days old seedling was found suitable for mechanical transplanting in terms of seedling mortality. Seedling height increased with the increase in seed density. BRRI dhan92 showed the highest stem thickness followed by BRRI dhan89 and BRRI dhan86 with seed rate 150 - 160 g per tray. The suitable seeding rate (150 - 160 g/tray) for the studied varieties was found better for raising mat-type seedlings suitable for mechanical transplanting, which could coordinate the production of larger population growth and higher harvest index to achieve high grain yield.

Determination of Optimum Seed Rate of Hybrid Rice (Oryza sativa L.) Varieties in Mat-Type Seedling Raising for Mechanical Transplanting

Rice is the most important and crucial to ensuring food and dietary energy security in most developing countries and is the staple food of more than half of the world’s population. This study was conducted to identify the seed rate of hybrid rice varieties for mechanical transplanting during Boro (irrigated dry season), 2021-22 season at BRRI research field, Gazipur. Slender grain type BRRI hybrid dhan3, BRRI hybrid dhan5, Ishpahani hybrid dhan6, and BRRI dhan89 were used in the study. The same growth medium was used to establish mat-type seedlings on plastic trays (280 × 80 × 25 mm) at seed rates of 80, 90, 100, 110, and 120 g∙tray−1. Walk-behind type 04 rows rice transplanter (Daedong, model-DP 488) was used during transplanting in the field at the set of the plant to plant spacing of 140 mm while line-to-line spacing was fixed to 300 mm. The result depicted that regardless of the variety, seedling density increased linearly as seed rate increased, except for the 21 days following sowing. However, the seedling density of BRRI dhan89 decreased after the seed rate of 100 g∙tray−1 due to mortality. The seedling height of the BRRI hybrids dhan5 and Ishpahani hybrid dhan6 was significantly higher than that of the BRRI hybrid dhan3 and BRRI dhan89. After 21 days, the seedling height decreased significantly with the increase in seed rate. For the seed rates of 100, 110, and 120 g∙tray−1, identical numbers of hills per unit area and plants per hill were observed. On the other hand, regardless of the variety, the percentage of missing hills considerably decreased with the increased seed rate. The yield of the BRRI hybrid dhan5 variety was significantly higher at the seed rates of 100 and 110 g∙tray−1, although the yield of the Ishpahani hybrid dhan6 variety was comparable. In terms of yield among the four varieties, BRRI hybrid dhan5 gave a higher yield followed by Ishpahani hybrid dhan6 while BRRI dhan89 gave a lower yield compared to the hybrid varieties irrespective of the seed rate. However, a seed rate of 110 g∙tray−1 gave a significantly higher yield followed by 120 g∙tray−1 while 80 and 90 g∙tray−1 gave lower grain yield. Generally, mat type seedling of inbred rice varieties is used in Bangladesh. The determination of seed rate of hybrid rice varieties may be increased by the use of rice transplanter in mechanical transplanting of hybrid rice varieties reducing the seed loss and increasing the grain yield.

Water Stress Effect on Biochemical Processes of Aus Rice Genotypes

An experiment was carried out at Sher-e-Bangla Agricultural University, Dhaka, Bangladesh during the period from March to July 2014. Plants were grown in the rain-protected polyethylene shelter or shed to avoid rain under natural conditions. The experiment was conducted on biochemical characters of aus rice varieties in various soil moisture levels in three rice genotypes as BRRI dhan55 (V1), BR6976-2B-15 (V2), and tolerant check Hashikalmi (V3), and seven water stress were imposed as treatments. Treatments were 0 days of water stress (control) irrigated continuously throughout the experimental period (T0). From twenty days onwards water stress was imposed for seven days when the age of the seedling was 20 days (T1), 35 days (T2), 55 days (T3), 75 days (T4), 95 days (T5), and 115 days (T6). Our findings suggest that the proline, starch, and sugar content were also found comparatively higher in BRRI dhan55 and Hashikalmi among the genotypes under water stress conditions. Under water stress conditions, proline was accumulated, sugar, and starch were decreased. The soluble sugar content was much lower under water stress conditions due to lower RWC, chlorophyll content, stomatal conductance, and higher leaf rolling. Leaf accumulates anthocyanins under drought conditions and the red color increased as the intensity of water stress increased.

Genome-Wide Analysis for Yield-Related Agronomic and Biochemical Traits of Chinese and Bangladeshi Grass Pea Genotypes Using SSR Markers

Grass pea(Lathyrus sativus L.)is an imperative food crop cultured in dryland agricultural ecology.It is a vital source of dietary protein to millions of populaces living in low-income countries in South-East Asia and Africa.This study highlights the improvement of genomic properties and their application in marker-trait relationships for 17 yield-related characters in 400 grass pea genotypes from China and Bangladesh.These characters were assessed via 56 polymorphic markers using general linear model(GLM)(P+G+Q)and mixed linear model(MLM)(P+G+Q+K)in the tassel software based on the linkage disequilibrium and population structure analysis.Population structure analysis showed two major groups and one admixed group in the populace.Statistically significant loci pairs of linkage disequilibrium(LD)mean value(D′)was 0.479.A total of 99 and 61 marker-trait associations in GLM and MLM models allied to the 17 traits were accepted at a 5%level of significance.Among these markers,21 markers were associated with more than one trait;12 marker-trait associations passed the Bonferroni correction threshold.Both models found six markers C41936,C39067,C34100,C47146,C47638,and C43047 significantly associated with days to maturity,flower color,plant height,and seed per pod were detected in the Hebei and Liaoyang location(p≤0.01),and the interpretation rate(R^(2)value)11.2%to 43.6%.Conferring to the consequences,the association analysis methodology may operative system for quantitative,qualitative,and biochemical traits related to gene position mapping and support breeders in improving novel approaches for advancing the grass pea quality.

Morphological, Cultural, Molecular and Pathogenic Variation of Bipolaris sorokiniana in Wheat

One hundred and twenty isolates of Bipolaris sorokiniana of wheat were isolated, identified and characterized based on morphological, cultural, pathogenic and ITS (Internal Transcribed Spacer) based molecular parameters. Collected isolates differed in respect of radial mycelial growth rate, color of the colony, surface texture of the colony, shape of the colony, conidia production ability and shape and color of conidia. ITS1 and ITS4 based PCR products yielded a species-specific band of 600 bp (base pairs) on agarose gel for the confirmation of B. sorokiniana. The mycelial growth rate of the isolates ranged from 1.39 to 4.46 mm/day. The septation of conidia ranged from 1.4 to 8.6. On the basis of conidia morphology, the isolates were grouped into five different groups, whereas the isolates were grouped into 12 cultural groups based on cultural characteristics. Cultural group 8 [CG (Cultural Group)-8] was the most virulent [38.5% LAD (Leaf area diseased)] and [CG (cultural Group)-4] was the less virulent [2% LAD (Leaf area diseased)] group among 12 groups when inoculated at tillering stage of wheat cv. Kachan.

Intercropping Empower Reduces Insect Pests and Increases Biodiversity in Agro-Ecosystem

Currently insect pest management solely depends on chemical pesticide that continuously affects on environment, biodiversity, animal as well as human health. Outbreak of secondary insect pest is also the cost of pesticide use in field leading crop more vulnerable to more pests. These negative impacts of pesticides have provoked growing interest in the adoption of multi-function agricultural biodiversity that promote pest management, creating interesting challenge for traditional approaches to regulatory compliance. To address multi-function agricultural practice, we tested several intercropping systems with mustard and their effect on pest management. Our results revealed that intercropping systems mustard with onion, garlic, radhuni and coriander significantly reduced pest population over sole crop. However, intercropping mustard with wheat and gram increased pest population in mustard field. This result indicated that all crops are not suitable for intercropping system. Among the tested intercropping systems, mustard with onion and coriander significantly reduced branch and flower infestation and increased pod formation per plant. These four intercropping systems did not significantly affect on honeybee pollinator which are crucial for mustard crop yield. A significant linear relationship was also found between honeybee population and pod formation. Our results indicate that suitable intercropping system can be a potential multi-functional agricultural practice for pest management in mustard crop.

Long-Term Effect of Industrial Waste Water Irrigation on Soil Chemical Properties

A laboratory experiment was conducted in Soil Science Division of BRRI during 2011 aimed to determine the vertical distribution of soil chemical properties under long-term industrial waste water irrigated rice field. Waste water irrigated rice field seemed to create some differences in soil pH profile. The pHW and pHKCl in all soil depth was higher with waste water irrigated rice field. The surface charge of both the soils was considerably negative. Waste water irrigated rice field developed more negative charges in soils. Irrigation with waste water increased Electrical Conductivity （EC） in rice soils profile. The organic carbon content （%） started to decrease sharply with the increase in soil depth. Organic carbon content was higher with waste water irrigated rice soils Total nitrogen （%） was high with underground water irrigated rice soils in surface but at deeper, total N was similar in both soils. Olsen P （mg/kg） was higher with underground water irrigated soil at 0-5 cm depth but at 5-100 cm soils profile, it was higher with waste water irrigated rice soils. Micronutrients （Zn, Fe, Cu and Mn） and heavy metals （Pb, Cd, Ni and Cr） in soils were increased significantly through irrigation with waste water in rice-rice cropping pattern.

An Analysis of Spatio-Temporal Trends of Land Surface Temperature in the Dhaka Metropolitan Area by Applying Landsat Images

Land surface temperature (LST) is a basic determinant of the global thermal behavior of the Earth surface. LST is a vital consideration for the appraisal of gradual thermal change for urban areas to examine the strength of the thermal intensity of the surface of urban heat island (SUHI) and to see how hot the surface of the Earth would be in a particular location. In this respect, the most developed urban city like Dhaka Metropolitan Area (DMA), Bangladesh is considered for estimation of LST, and Normalized Difference Vegetation Index (NDVI) changes trend in more developed and growing developing areas. The focus of this study is to find out the critical hotspot zones for further instantaneous analysis between these two types of areas. The trends of long-term spatial and temporal LST and NDVI are estimated applying Landsat images-Landsat 5-TM and Landsat OLI_TIRS-8 for the period of 1988 to 2018 for DMA and for developed and growing developing areas during the summer season like for the month of March. The supervised classification was used to estimate the land cover categories and to generate the LST trends maps of the different percentiles of LSTs over time using the emissivity and effective at sensor brightness temperature. The study found the change in land cover patterns by different LST groups based on 50th, 75th, and 90th percentile where the maximum LST for the whole DMA went up by 2.48°C, 1.01°C, and 3.76°C for the months of March, April, and May, respectively for the period of 1988 to 2018. The highest difference in LST was found for the most recently developed area. The moderate change of LST increased in the built-up areas where LST was found more sensitive to climate change than the growing developed areas. The vegetation coverage area decreased by 6.74% in the growing, developing areas compared to the developed areas from 1988 to 2018. The findings of the study might be helpful for urban planners and researchers to take up appropriate measures to mitigate the thermal effect on urban environment.

Ecological fitness of brown planthopper, Nilaparvata lugens (Stål), to rice nutrient management

Introduction:The brown planthopper(BPH),Nilaparvata lugens(Stål)(Hemiptera:Delphacidae),is a notorious insect pest of rice.Nutrient supplementation can alter plant biochemical compositions which may indirectly affect on ecological fitness parameters of its insect pest.However,few findings are available on nutrient-induced ecological fitness of BPH and relationship of BPH fitness parameters with its host rice plant biochemical contents.Methods:We studied the main and interaction effects of nitrogen(N),phosphorus(P),and potassium(K)inputs on BPH fitness,as measured by the following variables:nymph survival,nymphal duration,adult body weight,and its survival.Brown planthopper fitness parameters were regressed as function of rice plant(Oryza sativa)biochemical composition.A completely randomized design with four replications in a factorial scheme was used considering N,P,and K levels as factors.Results:Nitrogen application to the host rice plants provided greater survival and enhanced body weight of BPH.The nymphal duration was found to decrease with N subsidy that caused shorter generation time of BPH.Nitrogenous compounds N and soluble protein(SP),total free sugar(TFS),and silicon(Si)content in rice plant tissue correlated strongly with all fitness traits of BPH.Nitrogen,SP,and TFS associated positively with BPH survival and body weight,while negatively with nymphal duration.In contrast,Si had negative correlation with BPH survival and body weight,but positive with nymphal duration.Phosphorus supplementation to host plant contributed to increase BPH body weight.Relationships of P with all parameters of BPH were weak except body weight which was highly significant and positive.Interaction between N and P inputs demonstrated significant effect on BPH body weight.Application of K had no significant effect on BPH survival and development.Regression analysis did not detect significant relationship of BPH fitness parameters with plant tissue content of K.Conclusions:The results suggest that BPH ecological fitness characters were improved after N and P fertilization to rice plants which are associated with biochemical content of rice plant.Therefore,N and P inputs should be used judiciously in rice cultivation to keep BPH ecological fitness potential at minimum level.