Lowland rice is an important cereal crop that plays a key role in the food security and the economy of Thailand. Terminal water stress (TWS) in rainfed lowland areas poses threats to rice productivity due to stress occurrence at terminal crop stages and extreme sensitivity of rice to TWS. A two-year study was conducted to characterize the performance of yield and yield attributes of twelve Thai lowland rice genotypes under TWS, to identify stress-tolerant genotypes using stress response indices and to identify promising stress indices which are correlated with grain yield (GY) under well-watered (WW) and TWS conditions for their use as rapid identifiers in a rice crop breeding program for enhancing drought stress tolerance. Measurements were recorded under WW and TWS conditions. Highly significant variations were observed amongst assessed genotypes for their yield productivity responses. According to stress response indices, genotypes were categorized into stress-tolerant and stress susceptible genotypes. Genotypes Hom Pathum, Sang Yod, Dum Ja and Pathum Thani-1 were found highly stress tolerant and relatively high yielding; genotypes Look Pla and Lep Nok were stress tolerant, whereas genotypes Chor Lung, Hom Nang Kaew and Hom Chan were moderately tolerant genotypes. Hence, stress-tolerant genotypes could be potentially used for cultivation under rainfed and water-limited conditions, where TWS is predicted particularly in southern Thailand to stabilize rice productivity. Stress tolerance indices, including stress tolerance index (STI), geometric mean productivity (GMP), mean productivity index (MPRO) and harmonic mean index (MHAR), indicated strong and positive associations with GY under WW and TWS; thus, these indices could be used to indicate stress tolerance in rice crop breeding program aimed at a rapid screening of lowland rice genotypes for stress tolerance.

Crop models can provide rapid and cost effective means to deal with rice crop management. The objectives of this study included, exploring the ability of CSM-CERES-Rice in scheduling irrigation and to simulate the effect of drought stress on upland rice yield. Irrigation treatments 100, 70 and 50 % of field capacity (FC) were applied from 80 days after planting (DAP) at flowering stage until maturity and CSM-CERES-Rice was used to predict irrigation amount for each water regime for treatment duration. Results showed that, at 70 and 50 % FC, performance of an upland rice genotype, Dawk Payawm was decreased significantly as compared to 100 % FC. Normalized root mean square error (RMSEn) values less than 10 % for each treatment indicated a strong agreement between simulated and observed grain yield (GY) and biomass. d-index approaching to unity and RMSEn less than 10 % indicated a good agreement between simulated and observed soil moisture contents (SMC) for all irrigation treatments. Overall, it was concluded that drought stress had negative correlation with GY and CSM-CERES-Rice was able to predict irrigation amount for all treatments assuring that, model has potential for its use as a tool to schedule irrigation for experiments under water limited conditions.

The studies on interspecific competition of melon fly, Dacus cucurbitae Coq, and Ethiopian melon fly D. ciliatus Loew were carried out in the laboratory at 27±2±C and 65±5% R. H. The results on the superimposed restricted or unrestricted oviposition indicated that Ethiopian melon fly drastically suppressed the population of melon fly. The placement of equal number of eggs of both the species in the same fruit also indicated that Ethiopian melon fly larvae suppressed the development of melon fly larvae. Furthermore, lesser preoviposition and incubation periods and more reproductive potential of Ethiopian melon fly contributed towards the suppression of melon fly. It was concluded that the competition between Ethiopian melon fly and melon fly occurred in the larval stage. Zusammenfassung Interspezifische Konkurrenz zwischen Dacus cucurbitae Coq. und Dacus ciliatus Loew bei gleichzeitigem Befall von Kürbisfrüchten Die Untersuchungen zur interspezifischen Konkurrenz zwischen Dacus cucurbitae und D. ciliatus wurden im Labor bei 27 ± 2°C, 65 ± 5% R. H. durchgeführt. Wie die Ergebnisse einer uneingeschränkten bzw. einer eingeschränkten Eiablage beider Dacus‐Arten in jeweils gleiche Früchte zeigten, unterdrückt D. ciliatus sehr deutlich die Entwicklung von D. cucurbitae. Dies konnte auch durch die Übertragung einer gleichen Anzahl von Eiern beider Arten in eine Frucht gezeigt werden. Weiterhin ergibt sich aus der kürzeren Entwicklungszeit vor und nach der Eiablage sowie eines größeren Reproduktionsvermögens von D. ciliatus eine Überlegenheit gegenüber D. cucurbitae. Es wird angenommen, daß die Konkurrenz zwischen den beiden Arten im Larvenstadium auftritt.

Bioenergy from rice biomass feedstock is considered one of the potential clean energy resources and several small biomass-based powerplants have been established in rice–growing areas of Thailand. Rice production is significantly affected by drought occurrence which results in declined biomass production and quality. The impact of water stress (WS) was evaluated on six rice cultivars for biomass quality, production and bioenergy potential. Rice cultivars were experimented on in the field under well–watered (WW) and WS conditions. Data for biomass contributing parameters were collected at harvest whereas rice biomass samples were analyzed for proximate and lignocellulosic contents. Results indicated that WS negatively influenced crop performance resulting in 11–41% declined biomass yield (BY). Stability assessment indicated that cultivars Hom Pathum and Dum Ja were stress–tolerant as they exhibited smaller reductions by 11% in their BY under WS. Statistics for proximate components indicated a significant negative impact influencing biomass quality as ash contents of Hom Chan, Dum Ja and RD-15 were increased by 4–29%. Lignocellulosic analysis indicated, an increase in lignin contents of Hom Nang Kaew, Hom Pathum, Dum Ja and RD–15 ranging 7–39%. Reduced biomass production resulted in a 10–42% reduction in bioenergy potential (E). Results proved that cultivation of stress-susceptible cultivars or farmer’s choice and occurrence of WS during crop growth will reduce biomass production, biomass feedstock availability to biomass-based powerplants and affect powerplant’s conversion efficiency resulting in declined bioenergy production.

Rice is second most consumed cereal after wheat and it is considered as staple food in Thailand and most of the ASEAN countries. Analyzing yield performance of upland rice genotypes under field conditions is a key step in rice crop breeding program for improved rice production and ensuring food security. The objective of this research was to conduct a yield trial to assess performance of sixteen Thai upland rice genotypes under field conditions for further breeding process. Data from field trial that was conducted in 2016 in field research area

Vigorous and well-established nursery seedlings are an important component of sustainable oil palm production. We postulated that Si fertilization at the seedling stage could help to achieve improved performance of oil palm seedlings leading to healthy and vigorous nursery establishment. In this study, we evaluated the growth and physiological responses of oil palm Tenera hybrid seedlings under three Si fertilization treatments and a control including (i) 0 g Ca2SiO4 (T0), (ii) 0.5 g Ca2SiO4 (T1), (iii) 3.5 g Ca2SiO4 (T2), and (iv) 7.0 g Ca2SiO4 (T3) per plant per month. Ca2SiO4 was used as the Si fertilizer source and was applied for four consecutive months. Nondestructive data including stem diameter, plant height, leaf length, photosynthetic rate, leaf angle, and leaf thickness and destructive data including leaf, stem, and root fresh weight and dry weight, as well as chlorophyll a, Si, and nitrogen contents, were recorded before treatment (0 DAT), as well as 60 (60 DAT) and 120 days after treatment (120 DAT). Results indicated that Si fertilization enhanced Si accumulation in oil palm seedlings, and maximum accumulation was observed in the aerial parts especially the leaves with the highest accumulation of 0.89 % dry weight at T3. Higher Si accumulation stimulated the growth of seedlings; a total fresh weight of 834.28 g and a total dry weight of 194.34 g were observed at T3. Chlorophyll a content (0.83 gm−2) and net photosynthetic rate (4.98 µM CO2·m−2·s−1) were also observed at T3. Leaf morphology was not significantly influenced under Si fertilization, whereas the nitrogen content of seedlings was significantly increased. Correlation analysis revealed a highly significant and positive association among Si accumulation, chlorophyll a content, photosynthetic rate, total fresh weight, total dry weight, and nitrogen content of seedlings, indicating that Si fertilization enhanced the performance of these attributes. On the basis of the research evidence, it was concluded that Si fertilization should be considered for improved nutrient management for oil palm seedling and nursery production.

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Application of suitable nitrogen (N) fertilizer application rate (NR) with respect to sowing time (ST) could help to maximize the performance and productivity of upland rice in Southern Thailand. The 2-year experiments were conducted in the sheds to evaluate the agronomic responses of the upland rice genotype, Dawk Pa–yawm, under various combinations of NR and ST between 2018–2019 and 2019–2020 aimed at obtaining sufficient research evidence for the improved design of long-term field trials in Southern Thailand. As with the initial research, four NR were applied as N0 with no applied N, 1.6 g N pot−1, 3.2 g N pot−1 and 4.8 g N pot−1, and experiments were grown under three ST including early (ST1), medium (ST2) and late sowing (ST3). Results from the experiments indicate that the application of 4.8 g N pot−1 resulted in maximum grain yield under all ST in both years. However, a maximum increase in grain yield was observed under ST2 by 54–101% in 2018–2019 and by 276–339% in 2019–2020. Maximum grain N uptake of 0.57 and 0.82 g pot−1 was also observed at NR 4.8 g N pot−1 under ST2 in both years, respectively. Application of NR 4.8 g N pot−1 resulted in the highest N agronomic efficiency (NAE), nitrogen use efficiency (NUE) and water use efficiency (WUE). However, the performance of yield and yield attributes, N uptake, N use efficiencies and WUE were declined in late sowing (ST3). Significant positive association among yield, yield attributes, N uptake and WUE indicated that an increase in NR up to 4.8 g N pot−1 improved the performance of Dawk Pa–yawm. The results suggest that the application of 4.8 g N pot−1 (90 kg N ha−1) for upland rice being grown during September (ST2) would enhance N use efficiencies, WUE and ultimately improve the yield of upland rice. However, field investigations for current study should be considered prior to general recommendations. Moreover, based on the findings of this study, the importance of variable climatic conditions in the field, and the variability in genotypic response to utilize available N and soil moisture, authors suggest considering more levels of NR and intervals for ST with a greater number of upland rice genotypes to observe variations in field experiments for the precise optimization of NR according to ST.