Poramate Banterng

Seasonal variation in the dynamic growth and development traits of peanut lines

Physiological traits responsible for differences in yield performance among pre-released genotypes are normally not known. The objective of the present study was to evaluate seasonal variations in dynamic growth and development traits between 12 large-seeded Virginia-type and 14 small-seeded Spanish-type advanced breeding lines of peanut ( Arachis hypogaea L.). The experiment was conducted in 1999 and 2000 at Khon Kaen University in Northeast Thailand for three planting dates, representing the early-rainy season, mid-rainy season and dry season. Very similar phenological development was observed for all lines within each group and between the early and the mid-rainy seasons. However, a lower temperature during the early growth stage in the dry season delayed flower initiation and extended maturity. During this period, crop growth rates as well as the development rate for leaf area index and specific leaf area were also lower compared with the rainy seasons. On average, both pod yield and total biomass for the rainy season and the dry season were about the same. Variations among lines within each group were also small. For these advanced breeding lines, the pod growth rate was the most important yield determinant while the crop growth rate had lesser effect and the partitioning coefficient and pod-filling duration had no significant effect. However, the crop growth rate, pod growth rate and partitioning coefficient were important traits for a line to be the top yielder. Pod-filling duration was also important when the lines involved were considerably diverse in maturity and seed size. Information on these traits, if used together with final pod yield, will make varietal selection more efficient.

CSM-CERES-Rice model to determine management strategies for lowland rice production

The cropping system model, namely, the crop environment resource synthesis-rice (CSM-CERES-Rice) model, is a decision supporting tool for the design of crop management. This study aimed to determine management practices for increasing rice (Oryza sativa L.) production in Laos by using the CSM-CERES-Rice model. The model was evaluated with data sets from the TDK8 and TDK11 cultivars in farmers’ fields in the Vientiane plain in 2012. Anthesis and harvesting dates, growth and yield for various management scenario combinations (eight transplanting dates × two levels of plant densities × three rates of nitrogen (N) fertilizer application) for both cultivars were simulated by the model from 1980 to 2012. The model evaluation results showed strong agreement between simulated and observed data for days to harvest with a difference within four days. The model provided acceptable accuracy for grain yields with normalized root mean square error values ranging between 1 and 16 %. The results from the model application indicated that TDK8 and TDK11 produced similar yields. Transplanting TDK8 with two plant densities produced similar yields. The highest yield for both cultivars was achieved on the transplanting date of 15 Jan. N-fertilizer application at 60 and 120 kg N ha−1 was able to increase yield for TDK8 by 50 and 87 %, respectively, and for TDK11 by 54 and 70 %, respectively. Rice transplanted on 15 Jan with 5 seedlings hill−1 and N-fertilizer at 120 kg N ha−1 had the highest average yield for both cultivars with 6,460 and 6,351 kg ha−1 for TDK8 and TDK11, respectively. The CSM-CERES-Rice model is an alternative tool in determining crop management practices for rice production.

Ambiguity in a trans-disciplinary stakeholder assessment of neglected and underutilized species in China, Cambodia, Thailand and Vietnam

Neglected and Underutilized Crop Species (NUS) are grown primarily by traditional farmers in developing countries. They were once more widely grown but are today falling into disuse for a variety of agronomic, genetic, economic and cultural factors. While these crops continue to be maintained by socio-cultural preferences and use practices, most of them remain inadequately characterized and neglected by research and conservation. The aim of our work was to improve the agricultural portfolio by identifying promising neglected and underutilised species in China, Cambodia, Northeastern Thailand and Northern Vietnam. We began with preparing a “Masterlist” containing 260 species, based on farmer interviews and literature review. After an initial pre-selection we identified 17 NUS for China, 13 for Cambodia, 12 for Thailand, and 22 for Vietnam as of highest priority. These NUS then underwent a multi-criteria and trans-disciplinary assessment involving 511 stakeholders such as scientists, farmers, NGOs and policy makers. Based on the assessment we identified the most promising NUS for each country. We also identified some limitations for the promotion of so-called priority NUS regarding to some substancial disagreement between the involved stakeholders. In China and Cambodia, for example, farmers judged the potential of NUS significantly lower than other stakeholders, and in Vietnam scientists and policy makers had substantially different opinions on NUS compared to farmers. Addressing these ambiguous views will be highly relevant to the develoment of an improved agricultural portfolio.

Seasonal variation in photosynthesis performance of cassava at two different growth stages under irrigated and rain-fed conditions in a tropical savanna climate

Seasonal variations in photosynthesis of cassava cv. Rayong 9 (RY9) under irrigated and rain-fed conditions were evaluated at the age of three and six months after planting (MAP). Photosynthetic light-response (PN/I) curves revealed that cassava leaves attained the highest maximum net photosynthetic rates (PNmax) in the rainy season, followed by the hot one, while the lowest PNmax was found in the cool season. Photosynthetic potential of the 3-month-old plants was mostly higher than that of the 6-month-old plants, and the seasonal variation in photosynthetic capacity was also more apparent in the younger plants. PN/I curves were used to predict daily net photosynthetic rate (PN) for each season based on daily average solar radiation data. The predicted PN were considerably lower than the PNmax values. This indicated that solar radiation is a limiting factor for photosynthesis, particularly in the rainy season. The data provided basic information for breeding cassava genotypes with enhanced photosynthesis during the period of unfavorable environment. Furthermore, the data are potentially useful in modeling photosynthesis and crop growth as affected by environmental factors.