Reducing greenhouse gas emissions and improving rice yield: The influence of cultivars, soil salinity, and nitrogen management.

Rice is the most dominant field crop in Bangladesh covering 75% of the total cultivated area and consumes 80% of the total fertilizers alone. Nevertheless, the productivity of rice in Bangladesh remains one of the lowest in the world. Urea, the main source of nitrogen (N), plays a key role in rice production, is required in large amount, is the most limited nutrient and also suffers from heavy system losses when applied in the puddle field. A worldwide crisis of urea fertilizer in 2008 spurred the need to economize on its use with urgency. The Urea Deep Placement (UDP) technology is aimed at increasing N fertilizer use efficiency in rice production and thus holds the promise to economize on the use of a very important but finite resource (i.e., urea) while improving rice productivity. The present study econometrically measures the impact of recently introduced UDP technology on productivity and efficiency of modern rice cultivation at the farm-level in Bangladesh using a stochastic production frontier approach. Data were collected from Shimlagachi village in Sharsha upazilla (sub-district) of Jessore district, located 225 km southwest of capital Dhaka. A total of 100 farmers using UDP technology and another 100 farmers using conventional urea to produce rice in both Boro (dry winter) and Aman (monsoon) seasons were randomly selected. Detailed input-output data including socio-economic information of the farmers were collected through administering a pre-tested structured questionnaire. The survey was conducted during May-June 2013. Results reveal that net profit, productivity and technical efficiency are significantly higher for the farmers using UDP technology as compared with the conventional urea users. On average, productivity of UDP farmers is 13% higher (estimated at 7164 kg/ha and 5242 kg/ha for Boro and Aman seasons, respectively) than the conventional urea users. Profitability is also higher for UDP farmers (BCR estimated at 1.36 and 1.08 for Bor o and Aman seasons, respectively) than the conventional urea users (BCR estimated at 1.17 and 0.99 for Boro and Aman seasons, respectively). Finally, technical efficiency is 12% higher (estimated at 0.93) for the UDP farmers. However, the relative gain from UDP technology adoption is significantly higher in Boro season as compared with Aman season. The key policy conclusion is that the UDP technology should be disseminated widely with urgency so that Bangladesh can improve its food security by significantly increasing rice productivity while at the same time economize on the use of N fertilizer nutrient.

Rice is the principal staple crop, securing nutritional demand for more than half of the world's population. Due to unpredictable rainfall patterns, frequent flash floods, and higher acidity, rice production challenges are increasing day by day in Sylhet region of Bangladesh. A study was conducted in the haor area of Sylhet with 51 local and high yielding rice varieties (HYVs) in the Boro and Aman seasons. The experiment was arranged in randomized complete block design (RCBD) with three replications to observe phenology, yield characteristics, and yield of rice varieties. BRRI dhan85 (145.82 days), BRRI dhan84 (148.32 days), BRRI dhan81 (148.38 days), and local cultivars Tepi (128 days) and Rata (129 days) were short-duration Boro rice varieties. In contrast, BRRI dhan75 (117 days), BRRI dhan33 (122 days), BRRI dhan39 (126 days), and local cultivars Lalbinni (119.66 days) and Nazirshail (121 days) were short-duration Aman rice varieties. BRRI dhan29 (6.11 t ha-1), BRRI dhan28 (5.50 t ha-1), and BRRI dhan92 (5.50 t ha-1) showed maximum yield in Boro season, while BRRI dhan49 (4.59 t ha-1), BR22 (4.47 t ha-1), and BR11 (4.41 t ha-1) showed maximum yield in Aman season. BRRI Dhan85, Tepi, BRRI dhan39, and Nazirshail are short-duration and high-yielding rice varieties/cultivars among Boro HYVs, Boro local, Aman HYVs, and Aman local rice cultivars respectively. PCA revealed significant genetic variation where first three PCs accounted for 60% of total cumulative variability. PC1 and PC2 exhibited most of the variation (33% and 47% of the total cumulative variability). Cultivating these high yielding and short-duration rice could help to escape the impact of flash floods and increase the ultimate rice production in this region. J Bangladesh Agril Univ 23(2): 129-140, 2025

The selection of appropriate plant spacing may contribute to the yield potential of a rice variety. This experiment was conducted at the West Byde of BRRI farm, Gazipur during T. Aman’2017 and Boro' 2017-18 seasons to find out the optimum spacing of different short duration rice varieties. In T. Aman season the treatments were three rice varieties (V1 = BRRI dhan71, V2 = BRRI dhan75 and V3 = BINA dhan17) and five spacings (S1 = 15 cm × 15 cm, S2 = 20 cm × 15 cm, S3 = 20 cm × 20 cm, S4 = 25 cm × 20 cm and S5 = 25 cm × 25 cm). In boro season the treatments were four rice varieties (V1 = BRRI dhan81, V2 = BRRI dhan84, V3 = BRRI dhan86 and V4 = BRRI dhan28) and the spacings were same as T. Aman season. In each season, the treatments were arranged in a Split-plot design as variety in the main plots and spacing in the sub plots with three replications. In T. Aman season, irrespective of variety and spacing, the number of tillers per hill increased sharply and reached the maximum at 30 to 45 DAT then gradually decreased. BRRI dhan75 gave the highest grain yield which was statistically identical with the yield of BRRI dhan71 and BINA dhan17. The spacing 20 cm × 15 cm gave the highest grain yield compared to other spacing. On the other hand, during Boro season the number of tillers per hill increased sharply and reached the maximum at 60 to 80 DAT then gradually decreased. The 20 cm × 20 cm spacing gave the highest grain yield and among the varieties BRRI dhan84 gave the highest grain yield. Bangladesh Rice J.27(1): 75-83

Genetic analysis of 38 rice varieties released by the Bangladesh Rice Research Institute (BRRI) identified 34 as indica, 2 as admixed between indica and aus, and 4 as belonging to the aromatic/Group V subpopulation. Indica varieties developed for the two major rice-growing seasons, the wet monsoon (aman) and the dry winter (boro), were not genetically differentiated. The Additive Main Effect and Multiplicative Interaction (AMMI) model was used to assess the effect of genotype (G), environment (E) and genotype-environment interaction (GEI) on grain arsenic (As) concentration when these rice varieties were grown at ten BRRI research stations located across diverse agro-ecological zones in Bangladesh. G, E and GEI, significantly influenced grain As concentration in both seasons. Overall, E accounted for 69%–80%, G 9%–10% and GEI 10%–21% of the observed variability in grain As. One site, Satkhira had the highest mean grain As concentration and the largest interaction principle component analysis (IPCA) scores in both seasons, indicating maximum interaction with genotypes. Site effects were more pronounced in the boro than in the aman season. The soil level of poorly crystalline Fe-oxide (AOFe), the ratio of AOFe to associated As, soil phosphate extractable As and soil pH were important sub-components of E controlling rice grain As concentration. Irrespective of environment, the mean grain As concentration was significantly higher in the boro (0.290 mg As kg−1) than in the aman (0.154 mg As kg−1) season (p < 0.0001), though the reasons for this are unclear. Based on mean grain As concentration and stability across environments, the variety BR3 is currently the best choice for the boro season, while BR 23 and BRRI dhan 38 are the best choices for the aman season. Popular varieties BR 11 (aman) and BRRI dhan 28 and 29 (boro) had grain As concentrations close to the mean value and were fairly stable across environments, while high-yielding, short-duration aman season varieties (BRRI dhan 32, 33 and 39) developed for intensified cropping had relatively high grain As concentrations. Results suggest that genetic approaches to reducing As in rice grain will require the introduction of novel genetic variation and must be accompanied by appropriate management strategies to reduce As availability and uptake by rice.

A large landmass was formed at the downstream of Feni river due to the construction of Muhuri regulator at a cross dam in Mirsaraiupazila of Chittagong district. But this land is more vulnerable to storm and tidal surges leading to saline water intrusion. The study site was selected from this area to investigate the relationship between salinity and crop production. Soil samples were collected from different hydrological regimes such as old protected area, new protected area, unprotected area and affected area from topsoil, subsoil and substratum in both wet and dry period. Crop yield of the sampling plots were recorded through farmer’s interview. It was found that, salinity of the study area was less than 4 dS/m both in aman and rabi season. Rice is a semi-tolerant crop (it can tolerate salinity up to 4 dS/m). So no significant relationship between soil salinity and rice yield was observed. Farmers of this area mainly cultivate khesari crop in rabi season. A significant positive correlation (correlation coefficient 0.97) was found between the soil salinity and khesari yield in unprotected area. Water salinity inside the cross dam was around 0.1 dS/m (rabi season), which is considered excellent for irrigation. But outside the cross dam it ranged in between 4.8-5.4 dS/m in aman season and 12.4-20.8 dS/m in rabi season, which was extremely toxic for irrigation for the cultivation boro rice. Although soil salinity permits to cultivate HYV rice in a man season but water logging is the main constraint. HYV rice in boro season can be cultivated in old and new protected area by utilizing Feni river water inside the Muhuri regulator and closure dam for irrigation purpose. But in unprotected area, it can not be cultivated due lack of suitable irrigation water and tidal flooding. In the study area, non-irrigated crop like khesari can be grown successfully just after aman season by utilizing residual soil moisture.

Salinity causes cellular damage and limits crop productivity. Accumulation of organic compound is one of the adaptive mechanisms to salinity in plants. The experiments were laid out in a randomized complete block design with three replications at the farmer’s field of Botiaghata, Khulna to investigate the mitigating effects of organic manures on salinity stress in rice genotypes during both aman and boro seasons. Two T. aman rice (salt-sensitive; BR-23 and local cultivar; Mohini) and two boro rice (salt-sensitive; BRRI dhan-29 and salt-tolerant; BINA dhan-8) were used as test crops. Farmyard manure (FYM) and poultry manure (PM) were applied to the soils during final land preparation. There were five treatments namely T0= control (no manure), T1=FYM (5 t/ha), T2=FYM (10 t/ha), T3=PM (4 t/ha), T4=PM (8 t/ha).Thirtyday- old rice seedlings were transplanted in the experimental plots. Salinity caused a significant reduction in growth and yield of both aman and boro rice. Under saline condition, BR-23 (aman rice) produced higher yield than local cultivar Mohini in aman season while BINA dhan-8 produced higher yield than BRRI dhan29 in boro season. Soil amendments with FYM and PM significantly increased the growth, and grain and straw yields of all rice cultivars under saline conditions. Increased nutrient uptake and K+/Na+ ratio in rice were also observed due to application of organic manures. No considerable changes in post-harvest soil properties such as pH, EC, CEC and organic matter status of saline soils were observed by addition of FYM and PM. The present study suggests that soil amendments with FYM and PM improve salt tolerance in rice by increasing K+/Na+ ratio and nutrient uptake.&#x0D; Res. Agric., Livest. Fish.6(1): 11-17, April 2019

Leaching and runoff potential of nutrient and water losses in rice field as affected by alternate wetting and drying irrigation

Incidence of insect pests and their associated natural enemies was investigated from July 2017- June 2018 at six locations (Gazipur, Rajshahi, Barishal, Sonagazi, Rangpur, Cumilla) of Bangladesh to identify their major occurrence period as well as their incidence in three rice growing seasons, (Aus, T. Aman, and Boro). Among the tested locations, marked differences were found in the composition of insect pest and natural enemies. Higher number of pest population was found at Gazipur with 80,000 individuals for insect pest and 40,000 individuals for natural enemies. At least one peak for major insect pest and natural enemies suggested their specific occurrence period across the locations. Among the insect pests, major peak of GLH was found at Gazipur and Rajshahi during T. Aman season with 4,000 individuals for each location. In contrast, BPH population was as high as 10,000 individuals for Gazipur in October during T. Aman season. Additionally, it was high at Rajshahi in October and November with around 2,000 individuals of BPH. For WBPH, one major peak was found in October at Gazipur and Rajshahi with 10,000 and 2,000 individuals respectively. For YSB, it was higher at Rajshahi in October with over 6,000 individuals during T. Aman season. Moreover, one major peak also observed in Barishal with over 2,000 individuals in November. Among natural enemies, CDB population was observed mainly at three locations in between October and November with 900 individuals for Gazipur, 400 individuals for Rajshahi and 200 individuals for Barishal during T. Aman season. In contrast, for STPD population, two major peaks were found in Barishal with 6,000 and 5,000 individuals in December and March respectively during Boro season. For GMB population, it was observed at Gazipur in November with more than 20,000 individuals during T. Aman season whereas Rajshahi had around 2,000 individuals in the same month. However, higher incidence of GLH, BPH, and WBPH at Gazipur and Rajshahi suggested availability of insect pests during T. Aman season. In contrast, higher YSB incidence at Barishal and Rajshahi indicated their abundance in those areas. On the other hand, incidence of natural enemies at Gazipur indicated presence of greater biological control compared with other locations. In future, this information could serve as a reliable source in strengthening rice pest monitoring services as well as effective pest control in Bangladesh.&#x0D; Bangladesh Rice j. 2019, 23(1): 35-43

The study develops a model to estimate the growth of both production and adoption of modern rice varieties (MVs) in Bangladesh. Using secondary data on the level of adoption and production of MV rice and employing various statistical tools it was found that, out of three main rice crops (Aus. Aman and Boro). Boro has shown the fastest rate of growth in recent decades. The adoption of existing technologies has almost been exhausted. Furthermore, (a) MV adoption levels in the Aman season were below the centered moving average during the period 1972-94: (b) out of 21 greater districts of Bangladesh 17 had adoption levels below 50 percent in the 1990s and the figures ranged from 20 to 70 percent because the price of rice has gone up at a relatively low rate as compared to price of vegetables, spices and production inputs: (c) access to credit, availability of family labour. supplementary irrigation, soil type and rainfall are factors influencing MV T. Aman adoption levels across all the zones: and (d) cultivation of MV T. Aman is most profitable in the non-flood/nondrought zone as expected from known characteristics of MVs. Specific barriers to MV adoption in T. Aman season are tal varietal degradation due to seed contamination: (6) lack of location specific varieties: lcl lack of insect and disease-resistant varieties; and (d) lowprice of rice compared to other commodities (especially agricultural inputs) which make it difficult for tenant farmers to benefit from growing MV T. Aman rice. The research suggests that (i) location-specific and insect and disease-resistant varieties for T. Aman season need to be developed for the diverse agrqecological rice zones: (ii) the credit facilities be provided considering the amount of land devoted to MV rice than farm size: and (iii) rice farmers are to be motivated to grow BR-28, BR29 in Boro season, replacing the previous Boro varieties.

A farmer participatory research was conducted to determine the yield advantage of cleaned seeds over farmer-saved seeds in seven sites in Bangladesh in five cropping (three Boro and two transplant Aman) seasons. In each site, 30 participating farmers transplanted seedlings from cleaned seeds and their saved seeds of the same variety in adjacent plots in their fields. The results show a significantly higher grain yield in the cleaned seed than the farmer-saved seeds of 10.1% in Boro season and 11.3% in transplant (T) Aman season. The highest advantage in yield of cleaned seeds over farmer-saved seeds of 12.2% was observed in Barisal in Boro season, and 15.5% in Habiganj in T. Aman season. In the Boro season, significantly lower mean incidences of weeds below canopy, rice hispa, whiteheads, brown planthopper and bakanae were observed for cleaned seeds than for farmer-saved seeds. In the T. Aman season, significantly lower mean incidences of deadheart, whiteheads, gall midge, green leafhopper, other defoliators, sheath blight, sheath rot, and kernel smut were observed for cleaned seeds than for farmer-saved seeds. This indicates that using cleaned rice seeds increased grain yield, enhanced crop growth and also reduced damage from weeds, insect pests and diseases. Key words: Rice, seed health, quality, yield, farmer participatory research.

Five phosphorus rates (0, 5, 10, 20 and 30 kg P/ha) were tested with four rice genotypes in Boro (BRRI dhan36, BRRI dhan45, EH1 and EH2) and T. Aman (BRRI dhan30, BRRI dhan49, EH1 and EH2) season. Phosphorus rates did not influence grain yield irrespective of varieties in T. Aman season while in Boro season P response was observed among the P rates. Application of P @ 10 kg/ha significantly increased the grain yield. But when P was applied @ 20 and 30 kg P/ha, the grain yield difference was not significant. The optimum and economic rate of P for T. Aman was 20 kg P/ha but in Boro rice the optimum and economic doses of P were 22 and 30 kg/ha, respectively. Hybrid entries (EH1 and EH2) used P more efficiently than inbred varieties. A negative P balance was observed up to 10 kg P/ha. Key words: Response; Phosphorus fertilizer; Inbred; Hybrid rice DOI: http://dx.doi.org/10.3329/dujbs.v19i2.8962 DUJBS 2010; 19(2): 181-187

It has previously been reported that rice grown in regions of Bangladesh with low-arsenic (As) concentrations in irrigation water can have relatively high concentrations of As within their grains. This study aims to determine how widespread this issue is, and determine the seasonal variation in grain As in these regions. Levels of As were measured in shallow tube well (STW) water, soils, and rice grains collected during the Boro (dry) and Aman (wet) seasons from six Upazilas (sub-districts) of Bangladesh where As levels in groundwater were known to be low. In all the Upazilas, the As concentrations in STW water were <50 μg L−1. The As levels in soil samples collected from the Upazilas ranged between 0.2–4.0 mg kg−1 in the samples collected during the Boro season, and 0.4–5.7 mg kg−1 in the samples collected in the Aman season. Levels of As in both Boro and Aman rice grain varied widely: in Boro 0.02–0.45 mg kg−1, and in Aman 0.01–0.29 mg kg−1. Additionally, a household survey of dietary habits was also conducted in one Upazila by estimating As ingestion by 15 head female members. On average, the women consumed 3.1 L of water, 1.1 kg of cooked rice, and 42 g dry weight of curry per day. The total As ingestion rates ranged from 31.1–129.3 μg day−1 (mean 63.5 μg kg−1). These findings indicate that the major route of As ingestion in low groundwater-As areas of Bangladesh is rice, followed by curry and then water.

Boro rice (grown in winter under irrigated condition) contributes to the major portion of rice production (over 50%) in Bangladesh. Binadhan-17 is a green super rice developed by BINA which requires 30% less nitrogenous fertilizer and water which is grown in aman season (primely produced under rainfed). Due to it’s increasing popularity and adoption rice growers are keen to cultivate it in boro season also. Taking account of the above situation, two field trials were conducted at Magura during November 2019 to May 2020 to investigate the effect of variety, sowing dates and their interaction. Factorial RCBD (Randomized Complete Block Design) was applied for experimentation. Two rice varieties: Binadhan-17 (V1), BRRI dhan58 (V2) and three sowing times: 30th November (T1), 10th December (T2), 20th December (T3) were used as treatments. 35 days old seedlings were transplanted in main field. Relevant agronomic and morphological data were statistically analyzed through Statistix 10.0. Combined effect of the above factors at farm exposed that, T1×V1 required longest days (159.33 days) to mature. but, comparatively short life cycle (149.97 days) was observed by T3×V2. Maximum grain was yielded (7.70 t/ha) by T2×V1 and minimum (5.74 t/ha) by T1×V1 treatment combination. Outcomes of on station revealed that, T1×V1 needed more days (158.00 days) to mature; conversely, alike duration was noted with T2×V2 (147.20 days) and T3×V2 (145.43 days) which matured quite earlier. T2×V1 produced the highest grain yield (7.41 t/ha) and T1×V2 the lowest (5.94 t/ha). Our results indicate that, planting of Binadhan-17 on 10th December may give insect-disease free grains with optimum yield in context of Magura region. Farmers will be financially benefited if they cultivate this variety in the boro season in lieu of aman; due to higher yield

Proper nitrogen (N) management of high yielding rice varieties is crucial for obtaining their potential yield benefit. In this study, we compared the effect of different N rates on rice growth, yield, and N use efficiency of two high yielding rice varieties (BRRI dhan58 and BRRI dhan75) in a Boro (dry season)-fallow-T. Aman (wet season) cropping pattern. The N rates were: 0, 25, 50, 75, 100, 125, 150 and 175 kg ha−1 which were assigned in randomized complete block design with three replications. In Boro season, BRRI dhan58 showed higher response to applied N compared to BRRI dhan75 in T. Aman season. The calculated optimum N dose to maximize yield of BRRI dhan58 and BRRI dhan75 were 142 kg ha−1 and 82 kg ha−1, respectively. The agronomic N use efficiency and fertilizer N recovery efficiency were comparatively higher in BRRI dhan58 grown in Boro season than BRRI dhan75 grown in T. Aman season, while in both seasons, the N use efficiencies decreased with increased N rates. This study results suggest that variety-specific N fertilization with respect to growing season is the best N management practice to maximize rice yield avoiding the excess use of N fertilizer.

Photosensitive rice varieties have higher advantages in delayed planting. The present study was undertaken to figure out the degrees of delayed planting and evaluate the performance of six modern Aman rice varieties (BR11, BR22, BR23, BRRI dhan46, BRRI dhan54) against three sets of delayed planting. Each rice variety showed considerable variations for plant height, days to panicle initiation, flowering and maturity. BR22, BR23, and BRRI dhan54 showed a drastic reduction in days to panicle initiation and varied from 65 to 58 days, 69 to 60 days, and 62 to 55 days respectively, while it varied from 76 to 80 days for the control variety BR11. Similarly, days to flowering of BR22 and BRRI dhan54 showed a gradual decrease following different planting time and varied from 92 to 86 days, and 83 to 77 days respectively, while it varied from 109 to 107 days for the control variety BR11. For the above traits, BRRI dhan44 and BRRI dhan46 showed a moderate reduction depending on the three sets of planting time. Grain yield of BR22, BR23 reduced at the third set with a value ranging from 5.8 to 5.0 t/ha, 6.1 to 5.1 t/ha respectively, while BRRI dhan54 showed consistency in grain yield with a range from 5.3 to 5.2 t/ha. In contrast, grain yield of remaining rice varieties ranged between 5.7 to 4.5 t/ha for BRRI dhan46, 6.2 to 3.9 t/ha for BRRI dhan46 while severe reduction for the control variety BR11 with a range from 4.4 to 2.0 t/ha was observed. In conclusion, BRRI dhan54 was found more suitable rice variety in delayed planting compared with other photosensitive rice varieties. In future, BRRI dhan54 could be used as benchmark rice variety in a special rice breeding programme designed for delayed planting.&#x0D; Bangladesh Rice j. 2019, 23(1): 65-72