Kensuke Okada | The University of Tokyo (original) (raw)
Papers by Kensuke Okada
Tropical agriculture and development, 2020
Plant Production Science, Feb 15, 2021
ABSTRACT The self-sufficiency ratio and national average yield of wheat are low in Japan. Reducin... more ABSTRACT The self-sufficiency ratio and national average yield of wheat are low in Japan. Reducing the yield gap and receiving the government subsidy for grain quality are vital strategies for profitability. Elucidating optimum nitrogen application scheme is awaited to attain both higher yield and appropriate grain protein content (GPC) for wheat cultivation in Japan. Such decision support can be realized by integrating field experimental knowledge to crop growth models, although they have scarcely been utilized for wheat production in Japan. Therefore, the purposes of this study were to apply a widely used crop growth model (APSIM) to wheat growth on an Andosol in the Kanto region in Japan by calibration and validation. Selected model parameters of APSIM-wheat for phenology, leaf growth, and grain formation were readjusted based on the phenology and growth data of soft and hard wheat cultivars. Then the model was validated by using similar variables obtained in an independent experiment. For the simulation of the optimum sowing for winter wheat in the Kanto area (November), the root mean square error for grain yield was 23 and 48 g m−2 for Ayahikari and Yumeshiho varieties, respectively, and that for GPC was 1.9 and 1.4%. Thus, the overall model performance was acceptable for optimum sowing. However, grain yield and dry matter production were significantly overestimated when the data of late sowing groups were included. Therefore, further model improvement was suggested to add an algorithm to reduce the number of emerged plants under cold temperature in late sowing conditions. Graphical abstract
Springer eBooks, 2018
Developing rice production systems with efficient use of input resources such as water and nitrog... more Developing rice production systems with efficient use of input resources such as water and nitrogen is the pressing need worldwide. In Colombia, the contour-levee irrigation system in gently sloped land is widely used where the irrigation is applied in an intermittent manner and water is not stored continuously as in Asian paddy fields, and thus the utilization efficiencies of water and fertilizers are lower due to the surface drainage. Under the economic environment of increasing international competition for rice, it is required to decrease the production cost by increasing these efficiencies. For this purpose, the following researches are being conducted. First, the quantitative trait loci (QTL) related to root morphology and enhancing more roots at deeper soil layers are identified and introduced to the Colombian leading varieties to develop new-generation varieties. Second, a rice growth model is applied to the typical rice system, and better nitrogen management scheme is being developed through the scenario analysis by the simulation. Third, better irrigation methods are developed in the field, and their water-saving efficiencies in watershed scale are evaluated by using hydrological models. Fourth, the community precision agriculture and horizontal technology transfer methodologies are applied to the Colombian rice production system, and newly developed technologies are being integrated and disseminated in one of the major rice-producing region in Colombia. The new system is expected to be adopted by other Latin American countries where the similar irrigation systems are used.
Japanese Journal of Crop Science, 1980
Japanese Journal of Crop Science, 1980
To better understand interactions between crop duration and P nutrition of pigeonpea, response of... more To better understand interactions between crop duration and P nutrition of pigeonpea, response of a range of pigeonpea genotypes to P application was studied on an Alfisol and a Vertisol in peninsular India. Time to flowering was advanced by P application, more so in shorter duration genotypes and on Vertisol than Alfisol. In the Alfisol, P response of shoot biomass and grain yield was greater for extrashort-duration (ESD) than for short-duration (SD) genotypes. On this soil, P application depressed yield of the medium-duration (MD) genotypes. This occurred because the crops ran out of water. Plants were made more sensitive to water stress because there was less root proliferation at depth in P-fertilized, compared to unfertilized, treatments. By contrast, in the Vertisol extent of P response increased with crop duration. This was because of the greater water-holding capacity of this soil and thus increasing biomass formation, and demand for P, with increasing crop duration.
Agricultural Water Management, May 1, 2019
Contour-levee irrigation system is commonly used for rice cultivation in Latin American and Carib... more Contour-levee irrigation system is commonly used for rice cultivation in Latin American and Caribbean countries, but its water dynamics in commercial farm field settings are yet to be fully determined. This study aimed to investigate the water dynamics of the contour-levee irrigation system by analyzing conventional irrigation practices and by quantifying water balance and additionally to examine potential toposequential effects. Field experiments with different irrigation intervals were conducted on three commercial farms in Ibagué, Colombia for two seasons from 2017 to 2018. Irrigation and runoff water flows were constantly measured during the crop cycle using Parshall flumes with water level sensors. Percolation rate and field water table were measured using percolators and piezometers installed along the toposequence. The results showed that conventional irrigation management was highly flexible depending on soil permeability, rainfall, and agronomic factors, not particularly paying attention to ensure the flooded conditions during flowering period. The water balance resulted in the irrigation accounting for 76% of the total water input, whereas the runoff, ET, and percolation accounted for 40%, 21%, and 31% on overall average with considerable variation among the three farms. Percolation rates and duration with standing water did not show a clear and consistent tendency among the toposequential positions, but the percolation rate was significantly different among the farms corresponding to soil permeability. Consequently, clear toposequential effects on the water dynamics or on grain yield were not observed at the study site. To our knowledge, this study is the first to elucidate detailed water dynamics of contour-levee irrigation system in farm fields including toposequential difference.
To better understand interactions between crop duration and P nutrition of pigeonpea, response of... more To better understand interactions between crop duration and P nutrition of pigeonpea, response of a range of pigeonpea genotypes to P application was studied on an Alfisol and a Vertisol in peninsular India. Time to flowering was advanced by P application, more so in shorter duration genotypes and on Vertisol than Alfisol. In the Alfisol, P response of shoot biomass and grain yield was greater for extrashort-duration (ESD) than for short-duration (SD) genotypes. On this soil, P application depressed yield of the medium-duration (MD) genotypes. This occurred because the crops ran out of water. Plants were made more sensitive to water stress because there was less root proliferation at depth in P-fertilized, compared to unfertilized, treatments. By contrast, in the Vertisol extent of P response increased with crop duration. This was because of the greater water-holding capacity of this soil and thus increasing biomass formation, and demand for P, with increasing crop duration.
In the semi-arid tropics (SAT) of India. due to the uneven distribution of rainfall in the rainy ... more In the semi-arid tropics (SAT) of India. due to the uneven distribution of rainfall in the rainy season. crops gnrw under fluctuating soil moisture conditions. In the postrainy season, crops growing under decreasing soil moisture conditions are exposed to drought with the progression of growth. Poor physical conditions of soils such as surface sealing and Iow water-holding capacity of Alfisols and compaction of subsoil, low water infiltration and gas exchange rates of saturated V ertisols tend to enhance the effects of the fluctuations and decrease of the soil moisture. The low phosphorus fertility Ievel of Alfisols and V ertisols increases the susceptibility to drought by reducing the root growth of crops, especially cereals. Pigeonpea and chickpea have long been cultivated as essential components of cropping systems in the Indian SAT. Recently we were able to confirm that the cultivation of those two legumes resulted in the increase of the productivity of Alfisols and V ertisols t...
Agronomy Journal, 2016
The production of pearl millet [Pennisetumn glaucum (L.) R. Br.] in the low fertility sandy soils... more The production of pearl millet [Pennisetumn glaucum (L.) R. Br.] in the low fertility sandy soils of the Sahel region of northern sub‐Saharan Africa requires careful management. An experiment was established in 1993 at the Niamey Center of the International Crops Research Institute for the Semi‐Arid Tropics, Niger. The objectives were to (i) determine the effect of long‐term applications of fertilizer, crop residue, cattle manure, and combinations of these on changes in grain yield (GY) and total dry matter (TDM) of pearl millet; (ii) determine the effect of management on nitrogen application efficiency (NAE) and nitrogen use efficiency (NUE), using data from 1998 and also from 2005 and 2006. Fertilizer use showed significant positive effects on GY and TDM from 1998 to 2006. The positive effects of organic matter appeared rather later, that is, around 8 yr after the start of the experiment. The GY and TDM were strongly affected by N and P but not K. From 1998 to 2000, N‐fertilizer s...
Silicon in Agriculture, 2001
ABSTRACT
Books in Soils, Plants, and the Environment, 2005
The objectives of the Workshop were to discuss newly emerging concepts of the mechanisms that pla... more The objectives of the Workshop were to discuss newly emerging concepts of the mechanisms that plants use to acquire soil nutrients, and to relate those concepts in the context of applied agriculture. Some 40 papers and posters highlighting recent advances in this exciting field were presented. I greatly appreciate the efforts of the authors in critically evaluating the past work and presenting new experimental findings and concepts of both theoretical and applied significance. The scope of the Workshop was defined by the Organizing Committee-the members of which are the editors of this book-by holding regular discussions for one year prior to the Workshop. The Committee also received excellent professional support from several staff members and researchers of NIAES in organizing the Workshop. I express my sincere thanks to all of them. I am confident that this book will serve as a valuable reference for researchers, students, and extension staff in their efforts to develop more effective approaches to sustainable nutrient management.
Japanese journal of crop science, 1980
Japanese Journal of Crop Science, 1980
Introduction: In Japan wheat production is subsidized through “quality bonus” based on the grain ... more Introduction: In Japan wheat production is subsidized through “quality bonus” based on the grain quality including grain protein content (GPC). Recent researches attested that GPC can be increased by N application at flowering. However, it should be cautious with volcanic ash soils for its higher N supplying capacity. Here, the use of the crop growth model would be effective to compare different N management scenarios. We already parameterized (CSSJ Sep, 2014) and validated (CSSJ Mar, 2015) APSIM model for wheat production in Kanto area. The purposes of the present research are to find an optimal N regime that can produce required GPC and higher grain yield by comparing different simulation scenarios and to compare its yield and GPC with the results in the field experiment.
Tropical agriculture and development, 2020
Plant Production Science, Feb 15, 2021
ABSTRACT The self-sufficiency ratio and national average yield of wheat are low in Japan. Reducin... more ABSTRACT The self-sufficiency ratio and national average yield of wheat are low in Japan. Reducing the yield gap and receiving the government subsidy for grain quality are vital strategies for profitability. Elucidating optimum nitrogen application scheme is awaited to attain both higher yield and appropriate grain protein content (GPC) for wheat cultivation in Japan. Such decision support can be realized by integrating field experimental knowledge to crop growth models, although they have scarcely been utilized for wheat production in Japan. Therefore, the purposes of this study were to apply a widely used crop growth model (APSIM) to wheat growth on an Andosol in the Kanto region in Japan by calibration and validation. Selected model parameters of APSIM-wheat for phenology, leaf growth, and grain formation were readjusted based on the phenology and growth data of soft and hard wheat cultivars. Then the model was validated by using similar variables obtained in an independent experiment. For the simulation of the optimum sowing for winter wheat in the Kanto area (November), the root mean square error for grain yield was 23 and 48 g m−2 for Ayahikari and Yumeshiho varieties, respectively, and that for GPC was 1.9 and 1.4%. Thus, the overall model performance was acceptable for optimum sowing. However, grain yield and dry matter production were significantly overestimated when the data of late sowing groups were included. Therefore, further model improvement was suggested to add an algorithm to reduce the number of emerged plants under cold temperature in late sowing conditions. Graphical abstract
Springer eBooks, 2018
Developing rice production systems with efficient use of input resources such as water and nitrog... more Developing rice production systems with efficient use of input resources such as water and nitrogen is the pressing need worldwide. In Colombia, the contour-levee irrigation system in gently sloped land is widely used where the irrigation is applied in an intermittent manner and water is not stored continuously as in Asian paddy fields, and thus the utilization efficiencies of water and fertilizers are lower due to the surface drainage. Under the economic environment of increasing international competition for rice, it is required to decrease the production cost by increasing these efficiencies. For this purpose, the following researches are being conducted. First, the quantitative trait loci (QTL) related to root morphology and enhancing more roots at deeper soil layers are identified and introduced to the Colombian leading varieties to develop new-generation varieties. Second, a rice growth model is applied to the typical rice system, and better nitrogen management scheme is being developed through the scenario analysis by the simulation. Third, better irrigation methods are developed in the field, and their water-saving efficiencies in watershed scale are evaluated by using hydrological models. Fourth, the community precision agriculture and horizontal technology transfer methodologies are applied to the Colombian rice production system, and newly developed technologies are being integrated and disseminated in one of the major rice-producing region in Colombia. The new system is expected to be adopted by other Latin American countries where the similar irrigation systems are used.
Japanese Journal of Crop Science, 1980
Japanese Journal of Crop Science, 1980
To better understand interactions between crop duration and P nutrition of pigeonpea, response of... more To better understand interactions between crop duration and P nutrition of pigeonpea, response of a range of pigeonpea genotypes to P application was studied on an Alfisol and a Vertisol in peninsular India. Time to flowering was advanced by P application, more so in shorter duration genotypes and on Vertisol than Alfisol. In the Alfisol, P response of shoot biomass and grain yield was greater for extrashort-duration (ESD) than for short-duration (SD) genotypes. On this soil, P application depressed yield of the medium-duration (MD) genotypes. This occurred because the crops ran out of water. Plants were made more sensitive to water stress because there was less root proliferation at depth in P-fertilized, compared to unfertilized, treatments. By contrast, in the Vertisol extent of P response increased with crop duration. This was because of the greater water-holding capacity of this soil and thus increasing biomass formation, and demand for P, with increasing crop duration.
Agricultural Water Management, May 1, 2019
Contour-levee irrigation system is commonly used for rice cultivation in Latin American and Carib... more Contour-levee irrigation system is commonly used for rice cultivation in Latin American and Caribbean countries, but its water dynamics in commercial farm field settings are yet to be fully determined. This study aimed to investigate the water dynamics of the contour-levee irrigation system by analyzing conventional irrigation practices and by quantifying water balance and additionally to examine potential toposequential effects. Field experiments with different irrigation intervals were conducted on three commercial farms in Ibagué, Colombia for two seasons from 2017 to 2018. Irrigation and runoff water flows were constantly measured during the crop cycle using Parshall flumes with water level sensors. Percolation rate and field water table were measured using percolators and piezometers installed along the toposequence. The results showed that conventional irrigation management was highly flexible depending on soil permeability, rainfall, and agronomic factors, not particularly paying attention to ensure the flooded conditions during flowering period. The water balance resulted in the irrigation accounting for 76% of the total water input, whereas the runoff, ET, and percolation accounted for 40%, 21%, and 31% on overall average with considerable variation among the three farms. Percolation rates and duration with standing water did not show a clear and consistent tendency among the toposequential positions, but the percolation rate was significantly different among the farms corresponding to soil permeability. Consequently, clear toposequential effects on the water dynamics or on grain yield were not observed at the study site. To our knowledge, this study is the first to elucidate detailed water dynamics of contour-levee irrigation system in farm fields including toposequential difference.
To better understand interactions between crop duration and P nutrition of pigeonpea, response of... more To better understand interactions between crop duration and P nutrition of pigeonpea, response of a range of pigeonpea genotypes to P application was studied on an Alfisol and a Vertisol in peninsular India. Time to flowering was advanced by P application, more so in shorter duration genotypes and on Vertisol than Alfisol. In the Alfisol, P response of shoot biomass and grain yield was greater for extrashort-duration (ESD) than for short-duration (SD) genotypes. On this soil, P application depressed yield of the medium-duration (MD) genotypes. This occurred because the crops ran out of water. Plants were made more sensitive to water stress because there was less root proliferation at depth in P-fertilized, compared to unfertilized, treatments. By contrast, in the Vertisol extent of P response increased with crop duration. This was because of the greater water-holding capacity of this soil and thus increasing biomass formation, and demand for P, with increasing crop duration.
In the semi-arid tropics (SAT) of India. due to the uneven distribution of rainfall in the rainy ... more In the semi-arid tropics (SAT) of India. due to the uneven distribution of rainfall in the rainy season. crops gnrw under fluctuating soil moisture conditions. In the postrainy season, crops growing under decreasing soil moisture conditions are exposed to drought with the progression of growth. Poor physical conditions of soils such as surface sealing and Iow water-holding capacity of Alfisols and compaction of subsoil, low water infiltration and gas exchange rates of saturated V ertisols tend to enhance the effects of the fluctuations and decrease of the soil moisture. The low phosphorus fertility Ievel of Alfisols and V ertisols increases the susceptibility to drought by reducing the root growth of crops, especially cereals. Pigeonpea and chickpea have long been cultivated as essential components of cropping systems in the Indian SAT. Recently we were able to confirm that the cultivation of those two legumes resulted in the increase of the productivity of Alfisols and V ertisols t...
Agronomy Journal, 2016
The production of pearl millet [Pennisetumn glaucum (L.) R. Br.] in the low fertility sandy soils... more The production of pearl millet [Pennisetumn glaucum (L.) R. Br.] in the low fertility sandy soils of the Sahel region of northern sub‐Saharan Africa requires careful management. An experiment was established in 1993 at the Niamey Center of the International Crops Research Institute for the Semi‐Arid Tropics, Niger. The objectives were to (i) determine the effect of long‐term applications of fertilizer, crop residue, cattle manure, and combinations of these on changes in grain yield (GY) and total dry matter (TDM) of pearl millet; (ii) determine the effect of management on nitrogen application efficiency (NAE) and nitrogen use efficiency (NUE), using data from 1998 and also from 2005 and 2006. Fertilizer use showed significant positive effects on GY and TDM from 1998 to 2006. The positive effects of organic matter appeared rather later, that is, around 8 yr after the start of the experiment. The GY and TDM were strongly affected by N and P but not K. From 1998 to 2000, N‐fertilizer s...
Silicon in Agriculture, 2001
ABSTRACT
Books in Soils, Plants, and the Environment, 2005
The objectives of the Workshop were to discuss newly emerging concepts of the mechanisms that pla... more The objectives of the Workshop were to discuss newly emerging concepts of the mechanisms that plants use to acquire soil nutrients, and to relate those concepts in the context of applied agriculture. Some 40 papers and posters highlighting recent advances in this exciting field were presented. I greatly appreciate the efforts of the authors in critically evaluating the past work and presenting new experimental findings and concepts of both theoretical and applied significance. The scope of the Workshop was defined by the Organizing Committee-the members of which are the editors of this book-by holding regular discussions for one year prior to the Workshop. The Committee also received excellent professional support from several staff members and researchers of NIAES in organizing the Workshop. I express my sincere thanks to all of them. I am confident that this book will serve as a valuable reference for researchers, students, and extension staff in their efforts to develop more effective approaches to sustainable nutrient management.
Japanese journal of crop science, 1980
Japanese Journal of Crop Science, 1980
Introduction: In Japan wheat production is subsidized through “quality bonus” based on the grain ... more Introduction: In Japan wheat production is subsidized through “quality bonus” based on the grain quality including grain protein content (GPC). Recent researches attested that GPC can be increased by N application at flowering. However, it should be cautious with volcanic ash soils for its higher N supplying capacity. Here, the use of the crop growth model would be effective to compare different N management scenarios. We already parameterized (CSSJ Sep, 2014) and validated (CSSJ Mar, 2015) APSIM model for wheat production in Kanto area. The purposes of the present research are to find an optimal N regime that can produce required GPC and higher grain yield by comparing different simulation scenarios and to compare its yield and GPC with the results in the field experiment.