Thesis (M. Agr. Sc.)--University of Queensland, 2001. / Includes bibliographical references.

Rice produces a lot of biomass which is an important trait in increasing grain yield and it is a potential feedstock for bioenergy production. High biomass rice is important to meet the growing demands of grains and biomass for food, fodder and bio-fuel industries. Limited studies have been conducted to determine its response to unfavorable conditions. The main objectives of this study were to determine the response of selected high biomass rice to drought, rainfed and flooded conditions and identify best genotypes that can be grown in unfavorable areas. Two experiments were conducted in summer 2009 to evaluate biomass yield and agronomic traits of selected high biomass genotypes. A greenhouse study had genotypes grown under drought condition - different field capacity (FC) i.e. 100 percent, 75 percent and 50 percent FC, while the field study had rainfed and flooded environments. Most of the genotypes performed well under fully saturated soil conditions but some were less affected by drought. Limited water delayed first tiller emergence and reduced tiller count, rate of tiller production, plant height, rate of increase in height, shoot and root weight, root:shoot (R:S) ratio, percent dry matter (percent DM) and total biomass. The plant height, tiller plant-1, and total biomass at maturity were lower under rainfed conditions and their flowering was delayed compared to flooded conditions. Majority of these traits were correlated with high biomass yield. Genotype 11 which is tall and late maturing produced the highest number of tillers plant-1 and tillers/ 750 cm2 and had the highest biomass yield under both rainfed and flooded conditions. It performed equally well under drought conditions particularly in root and R:S ratio, but genotype 12 was the best in most parameters measured in the greenhouse. Although it was the shortest genotype, it was highest in biomass yield, earliest to tiller, had the highest shoot weight and tiller count, and had the fastest tiller production. The high biomass genotypes like conventional rice were affected by drought and performed better under flooded conditions. However, these two genotypes can produce optimum results under limited availability of water and hence be used for biomass production under stressed environments.

Kyoto University (京都大学) / 0048 / 新制・課程博士 / 博士(農学) / 甲第19044号 / 農博第2122号 / 新制||農||1032 / 31995 / 京都大学大学院農学研究科地域環境科学専攻 / (主査)教授 縄田 栄治, 教授 舟川 晋也, 教授 白岩 立彦 / 学位規則第4条第1項該当

京都大学 / 0048 / 新制・課程博士 / 博士(農学) / 甲第19044号 / 農博第2122号 / 新制||農||1032(附属図書館) / 学位論文||H27||N4926(農学部図書室) / 31995 / 京都大学大学院農学研究科地域環境科学専攻 / (主査)教授 縄田 栄治, 教授 舟川 晋也, 教授 白岩 立彦 / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DFAM

The proceedings included herein are the papers presented in the Seventh ICCAE Open Forum held in October 20th, 2006 at Nagoya University, Japan.

Drought and poor soil fertility are often cited as major constraints to rainfed lowland rice production in Laos, particularly in the central and southern parts of the country, where uncertainty in the growing season is common, due mainly to a combination of unreliable rainfall and coarse textured soils with a low water holding capacity and high rates of deep percolation. The soil conditions, together with fluctuations in rainfall distribution, are regarded as the most serious constraints to achieving high and stable grain yields in the rainfed lowland rice ecosystem in this region. Improvements in rainfed lowland rice productivity depend, in part, on improved predictions of water availability, as well as better understanding of soil nutrient and water stress limitations to grain yield. The use of a soil water balance model, in conjunction with the quantification of soil nutrient availability, can help in estimating free water levels in the rice fields, thereby helping determine the duration of the growing period, as well as, helping with predictions of potential yield reduction due to water stress and soil nutrient limitations. Linking the simulated results with Geographic Information System (GIS) can help quantify the spatial pattern of these attributes at a provincial or regional scale. This study was aimed at quantifying the spatial distribution of water availability, including the frequency and severity of water stress development during the growing period, and to estimate the effects of soil fertility and water stress on rice productivity in Savannakhet province in southern Lao PDR. The current status in relation to the variability in field water availability, soil fertility, farm crop management practices and grain yield throughout Savannakhet province were quantified, first by collecting farm data from 53 and 48 farmers’ fields in the 2007 and 2008 cropping seasons, respectively, These farms were selected to be representative of a wide range of soil and climate conditions within the province. The results show that rainfall distribution pattern, soil type and toposequence position of paddy fields, are crucial factors contributing to the temporal variation in field water availability. The overall yield loss due to water stress associated with late season drought was estimated to be rather small (10%, 5% and 3% for the top, middle and bottom toposequence positions of rice fields, respectively) in the 2008 wet season. On the other hand, application of chemical fertilizer has a large effect on final grain yield, with 50 kg N ha-1 and 30 kg P2O5 ha-1 increasing yield by 600 to 800 kg and 800 to 1000kg ha-1 respectively, in the 2007 and 2008 cropping seasons. A new soil water balance (SWB) model that incorporates the effect of low soil clay content on deep percolation, was developed to quantify field water availability and the length of growing period (LGP) for various rainfall lowland rice cropping environments. The model estimates the amount of water stored in a soil profile, the profile being divided into two layers: Layer 1 (0-200 mm) consists of standing water and the topsoil layer, while Layer 2 (200-1000 mm) is the subsoil layer. The SWB model was validated with field experimental data obtained in the 2002 and 2008 cropping seasons. The simulated free water levels were close to those recorded for the observed field data, with a small mean average error, lower root mean square error, and significant correlation coefficient and index of agreement over all sites across the three toposequence positions of paddy fields. Maps of the length, start and end of growing period (LGP, SGP and EGP, respectively) for rainfed lowland rice in Savannakhet province, were developed using the SWB model, with inputs of median weekly climatic data and soil water characteristics. The province was delineated into three main LGP zones with a short LGP zone (less than 21 weeks) in the east, northwest and some rice fields in the south-western corner of the province; an intermediate LGP zone (21 to 24 weeks) was defined in the central and western part of the province; and a long LGP zone (greater than 24 weeks) for the south and for some rice fields in the western part of the province. The variation in the SGP from year-to-year was due largely to the variation in rainfall early in the wet-season (e.g. April), while EGP was strongly dependent upon the clay content of the soils being cropped. The SWB model was combined with other models that estimate yield potential, soil nutrient supply and yield reduction by low soil water level, to characterize and map the suitability zones for rainfed lowland rice in Savannakhet province. The overall results of the model performance on yield estimates were satisfactorily, with a significant correlation coefficient (0.54**) and high index of agreement (0.68) over the 2007 and 2008 seasons. The model classified three main rice agro-ecological zones according to the suitability of climate and soil conditions. The majority of the lowland rice growing areas are classified as moderately suitable to marginally suitable, while the potential area classified as being high suitable is very small. A large potential response of rice yields to fertilizer inputs is predicted for most of rice growing areas in the province. The best sowing time for achieving a high yield, as evaluated by the model, is the first half of June. Appropriate crop phenology and increasing fertilizer use efficiency that matches with water availability and soil conditions in each rice agro-ecological zone, are important in achieving improvements in rice productivity, as substantial improvements in rice fields cannot be achieved by improving water availability alone, where paddy fields are dominated by soils with low level of indigenous fertility. Although the model is capable of quantifying field water availability and crop yield due to the limitations associated with low levels of soil nutrients and water stress, the model has the potential for further improvements in two areas. First, the estimates of water loss need to be modified by incorporating variable factors such as slope of paddy field, which can affects lateral water movement and hence free water level. Second, the model should incorporate some key agronomic variables, such as internal efficiencies and recovery efficiencies of applied fertilizer, which depend on variety, crop management and climatic conditions, and these factors can be modelled.

Drought and poor soil fertility are often cited as major constraints to rainfed lowland rice production in Laos, particularly in the central and southern parts of the country, where uncertainty in the growing season is common, due mainly to a combination of unreliable rainfall and coarse textured soils with a low water holding capacity and high rates of deep percolation. The soil conditions, together with fluctuations in rainfall distribution, are regarded as the most serious constraints to achieving high and stable grain yields in the rainfed lowland rice ecosystem in this region. Improvements in rainfed lowland rice productivity depend, in part, on improved predictions of water availability, as well as better understanding of soil nutrient and water stress limitations to grain yield. The use of a soil water balance model, in conjunction with the quantification of soil nutrient availability, can help in estimating free water levels in the rice fields, thereby helping determine the duration of the growing period, as well as, helping with predictions of potential yield reduction due to water stress and soil nutrient limitations. Linking the simulated results with Geographic Information System (GIS) can help quantify the spatial pattern of these attributes at a provincial or regional scale. This study was aimed at quantifying the spatial distribution of water availability, including the frequency and severity of water stress development during the growing period, and to estimate the effects of soil fertility and water stress on rice productivity in Savannakhet province in southern Lao PDR. The current status in relation to the variability in field water availability, soil fertility, farm crop management practices and grain yield throughout Savannakhet province were quantified, first by collecting farm data from 53 and 48 farmers’ fields in the 2007 and 2008 cropping seasons, respectively, These farms were selected to be representative of a wide range of soil and climate conditions within the province. The results show that rainfall distribution pattern, soil type and toposequence position of paddy fields, are crucial factors contributing to the temporal variation in field water availability. The overall yield loss due to water stress associated with late season drought was estimated to be rather small (10%, 5% and 3% for the top, middle and bottom toposequence positions of rice fields, respectively) in the 2008 wet season. On the other hand, application of chemical fertilizer has a large effect on final grain yield, with 50 kg N ha-1 and 30 kg P2O5 ha-1 increasing yield by 600 to 800 kg and 800 to 1000kg ha-1 respectively, in the 2007 and 2008 cropping seasons. A new soil water balance (SWB) model that incorporates the effect of low soil clay content on deep percolation, was developed to quantify field water availability and the length of growing period (LGP) for various rainfall lowland rice cropping environments. The model estimates the amount of water stored in a soil profile, the profile being divided into two layers: Layer 1 (0-200 mm) consists of standing water and the topsoil layer, while Layer 2 (200-1000 mm) is the subsoil layer. The SWB model was validated with field experimental data obtained in the 2002 and 2008 cropping seasons. The simulated free water levels were close to those recorded for the observed field data, with a small mean average error, lower root mean square error, and significant correlation coefficient and index of agreement over all sites across the three toposequence positions of paddy fields. Maps of the length, start and end of growing period (LGP, SGP and EGP, respectively) for rainfed lowland rice in Savannakhet province, were developed using the SWB model, with inputs of median weekly climatic data and soil water characteristics. The province was delineated into three main LGP zones with a short LGP zone (less than 21 weeks) in the east, northwest and some rice fields in the south-western corner of the province; an intermediate LGP zone (21 to 24 weeks) was defined in the central and western part of the province; and a long LGP zone (greater than 24 weeks) for the south and for some rice fields in the western part of the province. The variation in the SGP from year-to-year was due largely to the variation in rainfall early in the wet-season (e.g. April), while EGP was strongly dependent upon the clay content of the soils being cropped. The SWB model was combined with other models that estimate yield potential, soil nutrient supply and yield reduction by low soil water level, to characterize and map the suitability zones for rainfed lowland rice in Savannakhet province. The overall results of the model performance on yield estimates were satisfactorily, with a significant correlation coefficient (0.54**) and high index of agreement (0.68) over the 2007 and 2008 seasons. The model classified three main rice agro-ecological zones according to the suitability of climate and soil conditions. The majority of the lowland rice growing areas are classified as moderately suitable to marginally suitable, while the potential area classified as being high suitable is very small. A large potential response of rice yields to fertilizer inputs is predicted for most of rice growing areas in the province. The best sowing time for achieving a high yield, as evaluated by the model, is the first half of June. Appropriate crop phenology and increasing fertilizer use efficiency that matches with water availability and soil conditions in each rice agro-ecological zone, are important in achieving improvements in rice productivity, as substantial improvements in rice fields cannot be achieved by improving water availability alone, where paddy fields are dominated by soils with low level of indigenous fertility. Although the model is capable of quantifying field water availability and crop yield due to the limitations associated with low levels of soil nutrients and water stress, the model has the potential for further improvements in two areas. First, the estimates of water loss need to be modified by incorporating variable factors such as slope of paddy field, which can affects lateral water movement and hence free water level. Second, the model should incorporate some key agronomic variables, such as internal efficiencies and recovery efficiencies of applied fertilizer, which depend on variety, crop management and climatic conditions, and these factors can be modelled.

Thesis (M.Sc. Agriculture (Pasture Science)) -- University of Limpopo, 2021 / Finger millet (Eleusine coracana) is believed to be adapted to the arid and semi-arid regions, highly tolerant to pests, diseases and drought. It has the potential to produce a high forage biomass with fewer inputs under good production practices. The aim of the study was to evaluate the potential of finger millet as a fodder crop on the Pietersburg Plateau under rainfed and irrigation conditions, planted in rows and broadcast. The study was conducted for two consecutive seasons (2017 and 2018) at the Syferkuil Experimental Farm (SEF), University of Limpopo. Treatments consisted of two watering treatments (irrigation and rainfed) and two planting methods (broadcast and row planting). Seeding rate was 10 kg ha-1 with the inter row spacing of 25 cm. Irrigation had a significant effect on the dry matter production of finger millet (P ≤ 0.05). During 2017 growing season, under rainfed condition, the crop experienced zero production due to low rainfall. The total dry matter production of finger millet under rainfed conditions in 2018 was 3371 kg ha-1 for row planting and 3770 kg ha-1 for broadcasting. The dry matter production of finger millet under irrigation and row planting was 5318 kg ha-1 compared to 3371 kg ha-1 produced under row planting in the rainfed conditions. Broadcasting under irrigation produced 4890 kg ha-1 whereas broadcasting under rainfed conditions yielded 3770 kg ha-1. Planting method had no significant effect on the dry matter production of finger millet (P ≤ 0.05). The total dry matter production in 2017 was 5668 kg ha-1 and 5122 kg ha 1 under row planting and broadcast respectively, 2018 season produced the total dry matter production of 5122 kg ha-1 under row planting and 4892 kg ha-1 under broadcast. Finger millet planted under rainfed in rows had the CP% of 14.76 and 16.87% when broadcasted. In all the treatments CP% was higher than 10%. The ADF% was 33.02% under rainfed conditions and it ranged between 30.99% and 31.53% in 2017 and 2018 for row planting under irrigation. Finger millet can be considered an alternative fodder crop for livestock farmers in the Pietersburg Plateau

Agriculture is the mainstay of the economy in Malawi and accounts for 40% of the Gross Domestic Product (GDP) and 90% of the export revenues. Corn (maize) is the major cereal crop grown as staple food under rainfed conditions, covers over 92% of the total agricultural area, and contributes 54% of the caloric intake. Corn production is the principle occupation and major source of income for over 85% of the total population in Malawi. Issues of hunger and food insecurity for the entire nation are associated with corn scarcity and low production. Global warming is expected to cause climate change in Malawi, including changes in temperature and precipitation amounts and patterns. These climate changes are expected to affect corn production in Malawi. This study evaluates the impacts of climate change on rainfed corn production in Malawi. Lilongwe District, with about 1,045 square miles of agriculture area, has been selected as a representative area. First, outputs of 15 General Circulation Models (GCMs) under different emission scenarios are statistically downscaled. For this purpose, a weather generator (LARSWG) is calibrated and validated for the study area and daily precipitation as well as minimum and maximum temperature are projected for 15 GCMs for three time horizons of 2020s, 2050s and 2090s. Probability assessment of bounded range with known distributions is used to deal with the uncertainties of GCMs’ outputs. These GCMs outputs are weighted by considering the ability of each model to simulate historical records. AquaCrop, a new model developed by FAO that simulates the crop yield response to water deficit conditions, is employed to assess potential rainfed corn production in the study area with and without climate change. Study results indicate an average temperature increase of 0.52 to 0.94oC, 1.26 to 2.20oC and 1.78 to 3.58oC in the nearterm (2020s), mid-term (2050s) and long-term (2090s) future, respectively. The expected changes in precipitation during these periods are -17 to 11%, -26 to 0%, and -29 to -3%. Corn iii yields are expected to change by -8.11 to 0.53%, -7.25 to -14.33%, and -13.19 to -31.86%, during the same time periods. The study concludes with suggestion of some adaptation strategies that the Government of Malawi could consider to improve national food security under climate change.

京都大学 / 新制・論文博士 / 博士(農学) / 乙第13499号 / 論農博第2903号 / 新制||農||1093(附属図書館) / 学位論文||R4||N5405(農学部図書室) / (主査)教授 舟川 晋也, 教授 樋口 浩和, 准教授 真常 仁志 / 学位規則第4条第2項該当 / Doctor of Agricultural Science / Kyoto University / DFAM