Decadal changes in the rice-cropping system in the Ayeyarwady Delta using a large archive of satellite imagery from 1981 to 2020

In the last 40 years, the rice-cropping system has considerably changed in the Ayeyarwady Delta. The large archive of satellite imagery provides a history of how land and water resource managements have changed in the face of growing populations, resource demand, and climate change. This study aimed to assess the decadal changes in the rice-cropping system in the Ayeyarwady Delta by using the large archive of satellite imagery for the last 40 years (1981???2020). The long-term NDVI dataset provided various information on rice cultivation. Signal processing techniques were used to detect on the historical changes in the rice-cropping system, and the impact of climate change was assessed by using trend analysis. Until the 1980s, single-cropping of summer rice was dominant in the Delta. To enhance the grain yield of rice, the irrigation facilities were introduced in 1992 under an initiative of the Myanmar government. As a result, the annual cropping intensities increased from 1.087?±?0.390 in the 1980s to 1.422?±?0.499 in the 2010s. The information on historical change in the rice-cropping system would be useful to consider the practical and cost-effective utilization of remaining land and water resources. Moreover, the trend analysis of NDVI time-series showed negative trends in coastal areas. This indicates that the rice production in coastal areas has been constrained by the saline intrusion. The salt-affected areas are expected to expand under future climate change scenarios. Government support is highly required for sustainable rice production in the Delta.

     

棉铃虫四个丝氨酸蛋白酶抑制剂基因的克隆与表达分析

为明确棉铃虫Helicoverpa armigera丝氨酸蛋白酶抑制剂（serine protease inhibitor,serpin）的种类及其表达特性,利用PCR技术克隆棉铃虫的serpin基因,使用生物信息学软件预测其结构并进行系统进化分析,采用实时荧光定量PCR（real time quantitative PCR,RT-qPCR）技术比较serpin基因在棉铃虫不同发育阶段和组织中的表达量及取食Cry1Ac后其表达量的变化。结果表明,共获得serpin-a、serpin-b、serpin-c、serpin-e四个棉铃虫serpin基因,全长为1 119~1 254 bp,编码373~418个氨基酸,均包含一段具有反应中心环的保守结构域,且与斜纹夜蛾Spodoptera litura、草地贪夜蛾S.frugiperda等鳞翅目昆虫serpin的同源性较高。serpin-a和serpin-e在棉铃虫4龄幼虫期的表达量最高,serpin-b和serpin-c分别在成虫期和蛹期表达量最高。serpin-a在中肠和围食膜中表达量最高,serpin-b在头、中肠和表皮中表达量最高,serpin-c在头部表达量最高,serpin-e在中肠和血淋巴中的表达量显著高于其他组织。棉铃虫取食低浓度Cry1Ac后,中肠的serpin-b和serpin-e的表达量显著增加。推测不同serpin基因在棉铃虫不同发育时期和组织中可能发挥不同的作用,其中serpin-b和serpin-e可能参与棉铃虫对Cry1Ac的解毒过程。     

Impact of fresh and aged palm shell biochar on N2O emissions,soil properties,nutrient content and yield of Komatsuna (Brassica rapa var. perviridis) under sandy soil conditions

ABSTRACT

Biochar can reduce N₂O emissions and it can be added to the soil once, whereas fertilizers are often applied every cultivation season. The aging of biochar in soil affects its functioning but it is unclear whether palm shell biochar (PSB) could still mitigate N₂O emissions even when additional basal N fertilizers are applied 1 year after the initial biochar application. We studied the impact of fresh and aged PSB (0%, 6%, 12%, and 18% w/w of dry soil) on N₂O emissions, soil properties, nutrient content and yield of Komatsuna (Brassica rapa var. perviridis) under sandy soil conditions. The aged PSB non-significantly reduced N₂O emissions but significantly offset soil acidification, and maintained a high soil nutrient status. Biochar application with fertilizer significantly increased plant tissue K and Ca content but decreased N, P and Mg content compared to the treatments without biochar. At higher application rates, biochar had negative effects on crop yield but as it aged, the negative effects were offset as a result of the similar variation in plant N uptake. Since seasonal N fertilizer application seems to be inevitable in Komatsuna cultivation, addition of biochar could be a possible way of counteracting the effects of excessive fertilizer use. Further research is needed to assess the feasible biochar application rates for Komatsuna fields in various soil types under field conditions.     

Nitrate,nutrient content and growth parameters of komatsuna (Brassica rapa L.) in response to manure application depending on EMN (estimated mineralizable nitrogen)

We investigated the effects of poultry manures (PM) and cow manures (CM) using estimated mineralizable nitrogen (EMN) method on nitrate, nutrient content and growth parameters of komatsuna and compared with chemical fertilizer (CF) in an abandoned soil. We applied manures as EMN based on their total N content. The 100% of EMN by PM or CM enhanced dry matter (DM) but depressed nitrate content. The PM-Keifun (PMK) with total N (4.87%) produced greater growth parameters, DM, nutrient content and lower nitrate content but manures with total N (<2%) could not. The solo CF₁₅₀ did not promote leaf number but increased nitrate and Na content. In conclusion, a higher total N (>4%) concentration of manure led to increase availability and nutrient contents, DM, and depressed nitrate content of komatsuna, comparable with solo CF in an abandoned soil.     

Monitoring saline intrusion in the Ayeyarwady Delta,Myanmar, using data from the Sentinel-2 satellite mission

Paddy and Water Environment - Summer rice cannot be grown near the coast of the Ayeyarwady Delta, Myanmar, because of the high salinity in river water during the dry season. This means that saline...     

Effects of co-inoculation of Bradyrhizobium japonicum SAY3-7 and Streptomyces griseoflavus P4 on plant growth,nodulation, nitrogen fixation,nutrient uptake,and yield of soybean in a field condition

ABSTRACT

Co-inoculation of nitrogen-fixing bacteria with plant growth-promoting bacteria has become more popular than single inoculation of rhizobia or plant-growth-promoting bacteria because of the synergy of these bacteria in increasing soybean yield and nitrogen fixation. This study was conducted to investigate the effects of Bradyrhizobium japonicum SAY3-7 and Streptomyces griseoflavus P4 co-inoculation on plant growth, nodulation, nitrogen fixation, nutrient uptake, and seed yield of the ‘Yezin-6’ soybean cultivar. Nitrogen fixation was measured using the acetylene reduction assay and ureide methods. Uptake of major nutrients [nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg)] was also measured. This study showed that single inoculation of SAY3-7 significantly increased shoot biomass; nodulation; Relative Ureide Index (RUI %), percent nitrogen derived from N fixation (% Ndfa); N, P, K, Ca, and Mg uptakes; during the later growth stages (R3.5 and R5.5), compared with control. These observations indicate that SAY3-7 is an effective N-fixing bacterium for the plant growth, nodulation, and nitrogen fixation with an ability to compete with native bradyrhizobia. Co-inoculation of SAY3-7 and P4 significantly improved nodule number; nodule dry weight; shoot and root biomass; N fixation; N, P, K, Ca, and Mg uptake; at various growth stages and seed yield in ‘Yezin-6’ soybean cultivar compared with the control, but not the single inoculation treatments. Significant differences in plant growth, nodulation, N fixation, nutrient uptake, and yield between co-inoculation and control, not between single inoculation and control, suggest that there is a synergetic effect due to co-inoculation of SAY3-7 and P4. Therefore, we conclude that Myanmar Bradyrhizobium strain SAY3-7 and P4 will be useful as effective inoculants in biofertilizer production in the future.     

Characteristics of Livestock Husbandry and Management Practice in the Central Dry Zone of Myanmar

Tropical Animal Health and Production - The central dry zone of Myanmar is the area with the highest density of small-scale livestock farmers under harsh environmental condition. In this study, we...     

Effects of Integrated Organic and Inorganic Fertilizers on Yield and Growth Parameters of Rice Varieties

We investigated the effects of integrated organic and inorganic fertilizers on the growth and yield of indica rice variety Manawthukha and japonica rice variety Genkitsukushi. In a split-plot design, the two rice varieties were assigned as main plot factors, and the integrated treatments were the subplot factors, including no-N fertilizer(N_0), 50% chemical fertilizer(CF)(CF_(50)), 100% CF(CF100), 50% CF + 50% poultry manure(PM)(CF_(50)PM_(50)), 50% CF + 50% cow manure(CM)(CF_(50)CM_(50)), and 50% CF + 50% compost(CP)(CF_(50)CP_(50)). CF100 was equivalent to N at 85 kg/hm~2. Manure was applied based on the estimated mineralizable nitrogen(EMN) level, which is dependent on total N(%) of each manure type. Manawthukha rice plants were taller with higher tiller number and dry matter content. However, higher soil-plant analysis development(SPAD) values were measured in Genkitsukushi throughout the crop growth period, resulting in higher seed-setting rate(%) and greater yield. At the same N level, CF_(50)PM_(50) application in both rice varieties resulted in higher SPAD values, plant height and tiller number than CF_(100). CF_(50)PM_(50) containing total N more than 4% supplied synchronized N for the demands of the rice plants, resulting in maximum dry matter, yield and yield components. CF_(50)CM_(50) and CF_(50)CP_(50) treatments containing total N less than 4% resulted in lower yields which were similar to CF_(100). These results indicated that integrating organic and inorganic fertilizers enhanced growth parameters and yields of Manawthukha and Genkitsukushi, while reducing the dose of chemical fertilizer.     

Selection of type A and type B strains for improving symbiotic effectiveness on non-Rj and Rj4 genotype soybean varieties

The selection of effective rhizobia for higher efficiency nitrogen fixation is one of the most important steps for inoculant production. Therefore, this experiment was conducted to select the most effective type A and type B strains for specific Rj-gene harboring soybean varieties and to test the symbiotic effectiveness of selected strains on different Rj-gene harboring soybean varieties. Screening experiments using the specific soybean varieties were done with a completely randomized design and three replications in this study. Evaluation of the effective Myanmar Bradyrhizobium strains for plant growth, nodulation and N₂ fixation were studied in pot experiments using sterilized vermiculite in the Phytotron (controlled-environmental condition). Then, a pot experiment was conducted using Futsukaichi soil in the screen house (natural environmental condition). The N₂ fixation ability of soybean was evaluated by acetylene reduction activity (ARA) and the relative ureide index method. In the first screening experiment, type A and type B strains with higher nitrogen fixation and proper nodulation on their respective soybean cultivars were selected for the next screening. In the second screening, Bradyrhizobium elkanii AHY3-1 (type A), Bradyrhizobium japonicum SAY3-7 (type A), B. elkanii BLY3-8 (type B) and B. japonicum SAY3-10 (type B) isolates, which showed higher nitrogen fixation and nodulation in Yezin-3 (Rj₄) and Yezin-6 (non-Rj), were selected for the next experiment. In the third screening experiment, SAY3-7 and BLY3-8, which had higher nitrogen fixing potential and proper nodulation, were selected as effective isolates. These two isolates were compatible with non-Rj and Rj₄ soybean varieties for nodulation and nitrogen fixation. Based on the results of the screening experiment, these two strains were tested for their symbiotic efficacy in Futsukaichi soil. This study shows that inoculation treatment of SAY3-7 and BLY3-8 significantly increased plant growth, nodulation, and N₂ fixation at the V6, R3.5 and R8 stages in Yezin-3 (Rj₄) and/or Yezin-6 (non-Rj), and the seed yield at R8 stage, in Yezin-3 (Rj₄) and Yezin-6 (non-Rj) soybean varieties compared with the control treatment. It can be concluded that SAY3-7 and BLY3-8 are suitable for inoculant production because of their higher nitrogen fixation ability, proper nodulation and better productivity of Myanmar soybean cultivars.     

Investigating seasonal habitat-use of saltwater crocodiles in the Ayeyarwady Delta to identify potential conservation areas in Myanmar

1. Understanding the impact of land-cover mosaics on crocodile distribution and habitat patterns is essential to prioritize areas for their conservation in human-dominated landscapes. This is especially important for species with specialist requirements; or where there is human–wildlife conflict, as is the case in many areas with crocodiles, such as Myanmar's Ayeyarwady Delta.
2. The saltwater crocodile is used as a surrogate species in this study to identify important conservation areas, and to propose potential protected areas for the Ayeyarwady coastal mangrove ecoregion. In total, 684 locations of saltwater crocodile encounters were collected, 444 for the wet season (May to June), and 240 for the dry season (December to January) between 1999 and 2018. Suitable habitats of saltwater crocodiles in the Ayeyarwady Delta were modelled for wet and dry seasons, using 12 predictor variables at 300-m resolution.
3. The area of suitable habitat in the wet season is about 1,272.3 km² but reduces to 563.7 km² in the dry season. Distance to the cropland, distance to the sea, mangrove cover, and wetland cover are identified as the key landscape variables that contributed to the seasonal habitat distribution of saltwater crocodiles in the Ayeyarwady Delta.
4. Protecting core and buffer areas in Kadonkani Reserved Forest and Pyindayae Reserved Forest would safeguard the seasonal habitats of saltwater crocodiles. Khaing Thaung Island, an unprotected area with suitable habitat areas for saltwater crocodiles, is proposed as a potential marine protected area in the Ayeyarwady Delta of Myanmar.