In this study, we define the cardinal temperatures and thermal time for germination and emergence... more In this study, we define the cardinal temperatures and thermal time for germination and emergence of pigeonpea genotypes. Seeds of six genotypes were subjected to constant temperatures ranging between 5 and 50°C in petri dishes with filter paper (germination) and with media (emergence) were placed in a thermal gradient plate. A nonlinear bent-stick model fitted to the rate of development to germination and emergence resulted in parameters predicting cardinal temperatures including base (Tb), optimum (To), maximum (Tm), and thermal time. Estimated Tb for 50% germination and emergence were 8.4 and 10.8°C, respectively, with no significant differences between genotypes. Optimum temperatures were 33.8 and 37.9°C for germination and emergence, respectively, with genotypes differing significantly. Thermal time for 50% germination and emergence varied significantly among genotypes. The results suggest that genotypic responses to the temperature are typical for their tropical origin and hen...
The major objective of this experiment was to identify optimum plant population densities for dif... more The major objective of this experiment was to identify optimum plant population densities for different maize maturity groups depending on the environments’ potential and identify situations that reduce risk of crop failures while maximizing opportunities for better yield when weather conditions are good.
The present study investigated if partial reduction of shoot dry matter during early vegetative g... more The present study investigated if partial reduction of shoot dry matter during early vegetative growth phase of chickpea crop (cv. PBA Seamer) saves subsoil water for reproductive growth and grain filling of the crop grown at 9 diverse environments. The environments were created by a combination of 3 sites (Emerald, Hermitage and Kingaroy), 3 planting windows (environments 1, 2, 3 at each site) with and without supplementary irrigation. The effects of environments on canopy management (partial reduction in shoot dry matter vs control) and irrigation treatments on the water uptake by roots, crop growth and yield performance and yield components were investigated. Crops in the planting windows (EN 1, 2, 3) experienced variable environments at each site. Days to 50% flowering and crop maturity reduced progressively from EN 1 to EN 3 at the three sites. The environment had significant effect on shoot biomass, yield and HI at the three sites (P < 0.01 or P < 0.0001). Environments had bigger effects on crop that partial reduction in shoot biomass (PRS). The PRS at early vegetative phase resulted in a 25% reduction in radiation intercepted but rapid compensatory growth that followed, resulted in minimal effect on shoot biomass and yield. The HI varied from 0.18 in EN 1 at Kingaroy to > 0.5 in EN 2 at Emerald. There was a trend for an increase in HI from EN 1 to EN 3 at all sites. The response to Irr, computed as the difference in peak shoot biomass and yield between the Irr and RF treatments, was the highest at Hermitage and the least at Emerald site. Vapour pressure deficit during reproductive phase accounted for the majority of variation in shoot biomass response to irrigation (r 2 = 0.66, P < 0.001) for total dry matter and (r 2 = 0.46, P < 0.01) for yield. The environments had a significant effect on radiation use efficiency and water use efficiency and the yield components including hundred seed weight.
Abstract Literature on financial economics suggests that market participants tend to suppress the... more Abstract Literature on financial economics suggests that market participants tend to suppress their own information and try to imitate others in the market, thereby herding against their private information. This tendency is attributed to risk aversion characteristic of economic agents that rely more on short cuts and heuristics in order to avoid risk of losing time required to incorporate private information. Such a tendency also results in the asymmetric expected returns on assets. We attempt to find empirical evidence of herding in two different cross-sections of financial markets using cross-sectional deviations of stock returns to measure the dispersion of individual stock returns from average market return. Using a unique dataset of daily stock returns from January 2011 to December 2015, we examine the small and large-cap stocks for the effect of herding. We study the existence of herding in two cross-sections of stocks in the Indian stock market and show that stocks with robust fundamentals observe little or negligible evidence of herding while vulnerable stocks are evidently found to be affected by herding. While examining herding, we show whether the cross-sectional dispersion of stock returns in large-cap stocks are lower compared to that in small-cap stocks, implying stocks with higher market capitalization and trading volume are less prone to herding.
Maize is the main staple food crop grown by smallholder farmers in Ethiopia. High variability in ... more Maize is the main staple food crop grown by smallholder farmers in Ethiopia. High variability in inter-seasonal rainfall presents the biggest risk for farmers to invest in best management practices in maize crop grown in Ethiopia. Optimising genotype (G) and management (M) of maize for different growing environments (E) could alleviate risks associated with seasonal rainfall variability and enhance reliability of yield of this crop. The objectives of this study were to quantify G x E x M interactions and identify best combinations of G and M for target maize production environments in Ethiopia. Ten genotypes, five each from early and medium maturity classes were evaluated at five planting densities, 2, 5, 6, 7 and 9 plants m −2 , across seven environments in 2013 and 2014 cropping seasons. Our study explored a range of morphological, phenological and physiological traits underpinning the yield of maize. Our results revealed that combining the appropriate G and M is more effective than relying on the choice of genotypes. The optimum plant densities identified in this study are higher than the plant densities currently used by farmers. Planting BH-546 and TH13321 at 7 plants m −2 substantially increased yield compared with other genotypes. For instance, yield for TH13321 was higher by 48% (3.7 t ha-1) at 7 plants m −2 in high yielding environments compared with BH-540, the most widely grown hybrid by farmers. This indicates the need for optimising G and M and using versatile genotypes to exploit variability in weather and input-use in the country. The genotypes substantially varied for their response to radiation use efficiency, rainwater productivity and leaf orientation value at high plant density. The least response to these traits observed for BH-540 highlights the need for a reassessment of current varietal and agronomic options for maize production in Ethiopia. Information from this study could be extended to sub-Saharan African countries that are similarly using low plant density.
High inter-seasonal rainfall variability presents the biggest risk for farmers to invest in best ... more High inter-seasonal rainfall variability presents the biggest risk for farmers to invest in best management practices in maize grown in much of Ethiopia. Optimising genotype (G) and management (M) of maize for different growing environments (E) could alleviate risks associated with seasonal rainfall variability and enhance reliability of production of this crop. In this study, we explored this possibility with the help of the APSIM maize model. The model was first calibrated and then tested on different sets of data for its ability to simulate phenology, dry matter and yield of six genotypes of differing maturity grown under rainfed conditions at four plant densities at four sites including Bako, Hawassa, Melkassa and Adamitulu in Ethiopia in 2013 and 2014. The model accurately predicted plant available soil water (NRMSE = 6%), days-to-flowering (NRMSE = 4%), days to maturity (NRMSE = 4%), leaf area index (NRMSE = 6%), biomass (NRMSE = 13%) and yield (NRMSE = 5%). The simulations revealed that increasing plant density increased water use efficiency of genotypes at all sites. The model in conjunction with site-specific soil properties and 33 years of daily weather data was then used to simulate changes in the water supply demand ratio to determine dominant drought patterns at each site which could be clustered into four major drought patterns. These drought patterns included low stress occurring in 55% of the seasons, mid-season occurring in 11% of the seasons, early terminal drought in 17% of the seasons, and late terminal drought 17% of the seasons. The frequencies of these drought patterns varied at different sites. These could also be manipulated by genotypes of different maturity and plant density resulting in different yield outcomes at each site. The study revealed significant scope for yield improvement by manipulating G and M, with larger effects in favourable seasons.
Maize is a staple food crop in eastern and southern Africa with significant contribution for food... more Maize is a staple food crop in eastern and southern Africa with significant contribution for food security of this vast region. Efforts to breed superior maize cultivars for the region are challenged by high genotype x environment interactions arising mainly due to variable soil moisture supply caused by high temporal and spatial variability in rainfall. Information on major drought patterns and their frequencies, which can assist in dealing with such interactions in the region, however, is not available. The objectives of this study were therefore to (i) identify major drought patterns and their frequencies, (ii) identify iso-environments based on the similarity of drought patterns and (iii) explore scope for yield improvement through optimising genotype and management in various drought patterns. We used the well validated APSIM model to characterise major drought patterns and their frequencies experienced by maize cropping systems in the target population of environments spread across six countries of the region including Ethiopia, Kenya, Tanzania, Malawi, Mozambique and Zimbabwe. The database used for the model simulations consisted of 35 locations, 17-86 years of daily climate records and three cultivars. The dynamic changes in water supply-demand ratio in each season was simulated against the thermal time for each cultivar across the 35 locations and clustering analysis was used to cluster the major drought patterns. The analysis identified four major drought patterns characterised by low-stress, mid-season drought, late terminal drought and early-terminal drought patterns, occurring at 46%, 11%, 22% and 21% of the years, respectively. The frequencies of these patterns varied in relation to locations, genotypes and management. Yield reduction of up to 80% was observed for early terminal drought compared with low-stress drought pattern. There was significant scope for yield improvement through manipulating genotype and management. These results have important implications for germplasm enhancement and deployment over similar environments in the region.
Chickpea (Cicer arietinum L.) has been traditionally grown in India but is a relatively new expor... more Chickpea (Cicer arietinum L.) has been traditionally grown in India but is a relatively new export crop in Australia where its cultivation is expanding into new areas. The objective of this study was to identify homoclimes (i.e. similar chickpea-growing environments) in the major chickpea-growing areas of the 2 countries, using the Agricultural Production Systems Simulator (APSIM) chickpea model. The model, which processes climatic, soil, and plant information on a daily time step, was first validated and then used to simulate flowering, maturity, and grain yield of Amethyst, a mid-season cultivar, and Barwon, a full-season cultivar, on low (100 mm), medium (150 mm), and high (190 mm) water-holding capacity soils, using historical climatic data of 67 Australian and 24 Indian locations. The mean of annual outputs of flowering, maturity, and grain yield of the 2 cultivars on 3 soils was then clustered using Ward’s hierarchical complete linkage clustering procedure. At a 90% level of s...
Australian Journal of Experimental Agriculture, 2007
Measurement or accurate simulation of soil temperature is important for improved understanding an... more Measurement or accurate simulation of soil temperature is important for improved understanding and management of peanuts (Arachis hypogaea L.), due to their geocarpic habit. A module of the Agricultural Production Systems Simulator Model (APSIM), APSIM-soiltemp, which uses input of ambient temperature, rainfall and solar radiation in conjunction with other APSIM modules, was evaluated for its ability to simulate surface 5 cm soil temperature in 35 peanut on-farm trials conducted between 2001 and 2005 in the Burnett region (25°36′S to 26°41′S, 151°39′E to 151°53′E). Soil temperature simulated by the APSIM-soiltemp module, from 30 days after sowing until maturity, closely matched the measured values (R2 ≥ 0.80) in the first three seasons (2001–04). However, a slightly poorer relationship (R2 = 0.55) between the observed and the simulated temperatures was observed in 2004–05, when the crop was severely water stressed. Nevertheless, over all the four seasons, which were characterised by...
In this study, we define the cardinal temperatures and thermal time for germination and emergence... more In this study, we define the cardinal temperatures and thermal time for germination and emergence of pigeonpea genotypes. Seeds of six genotypes were subjected to constant temperatures ranging between 5 and 50°C in petri dishes with filter paper (germination) and with media (emergence) were placed in a thermal gradient plate. A nonlinear bent-stick model fitted to the rate of development to germination and emergence resulted in parameters predicting cardinal temperatures including base (Tb), optimum (To), maximum (Tm), and thermal time. Estimated Tb for 50% germination and emergence were 8.4 and 10.8°C, respectively, with no significant differences between genotypes. Optimum temperatures were 33.8 and 37.9°C for germination and emergence, respectively, with genotypes differing significantly. Thermal time for 50% germination and emergence varied significantly among genotypes. The results suggest that genotypic responses to the temperature are typical for their tropical origin and hen...
The major objective of this experiment was to identify optimum plant population densities for dif... more The major objective of this experiment was to identify optimum plant population densities for different maize maturity groups depending on the environments’ potential and identify situations that reduce risk of crop failures while maximizing opportunities for better yield when weather conditions are good.
The present study investigated if partial reduction of shoot dry matter during early vegetative g... more The present study investigated if partial reduction of shoot dry matter during early vegetative growth phase of chickpea crop (cv. PBA Seamer) saves subsoil water for reproductive growth and grain filling of the crop grown at 9 diverse environments. The environments were created by a combination of 3 sites (Emerald, Hermitage and Kingaroy), 3 planting windows (environments 1, 2, 3 at each site) with and without supplementary irrigation. The effects of environments on canopy management (partial reduction in shoot dry matter vs control) and irrigation treatments on the water uptake by roots, crop growth and yield performance and yield components were investigated. Crops in the planting windows (EN 1, 2, 3) experienced variable environments at each site. Days to 50% flowering and crop maturity reduced progressively from EN 1 to EN 3 at the three sites. The environment had significant effect on shoot biomass, yield and HI at the three sites (P < 0.01 or P < 0.0001). Environments had bigger effects on crop that partial reduction in shoot biomass (PRS). The PRS at early vegetative phase resulted in a 25% reduction in radiation intercepted but rapid compensatory growth that followed, resulted in minimal effect on shoot biomass and yield. The HI varied from 0.18 in EN 1 at Kingaroy to > 0.5 in EN 2 at Emerald. There was a trend for an increase in HI from EN 1 to EN 3 at all sites. The response to Irr, computed as the difference in peak shoot biomass and yield between the Irr and RF treatments, was the highest at Hermitage and the least at Emerald site. Vapour pressure deficit during reproductive phase accounted for the majority of variation in shoot biomass response to irrigation (r 2 = 0.66, P < 0.001) for total dry matter and (r 2 = 0.46, P < 0.01) for yield. The environments had a significant effect on radiation use efficiency and water use efficiency and the yield components including hundred seed weight.
Abstract Literature on financial economics suggests that market participants tend to suppress the... more Abstract Literature on financial economics suggests that market participants tend to suppress their own information and try to imitate others in the market, thereby herding against their private information. This tendency is attributed to risk aversion characteristic of economic agents that rely more on short cuts and heuristics in order to avoid risk of losing time required to incorporate private information. Such a tendency also results in the asymmetric expected returns on assets. We attempt to find empirical evidence of herding in two different cross-sections of financial markets using cross-sectional deviations of stock returns to measure the dispersion of individual stock returns from average market return. Using a unique dataset of daily stock returns from January 2011 to December 2015, we examine the small and large-cap stocks for the effect of herding. We study the existence of herding in two cross-sections of stocks in the Indian stock market and show that stocks with robust fundamentals observe little or negligible evidence of herding while vulnerable stocks are evidently found to be affected by herding. While examining herding, we show whether the cross-sectional dispersion of stock returns in large-cap stocks are lower compared to that in small-cap stocks, implying stocks with higher market capitalization and trading volume are less prone to herding.
Maize is the main staple food crop grown by smallholder farmers in Ethiopia. High variability in ... more Maize is the main staple food crop grown by smallholder farmers in Ethiopia. High variability in inter-seasonal rainfall presents the biggest risk for farmers to invest in best management practices in maize crop grown in Ethiopia. Optimising genotype (G) and management (M) of maize for different growing environments (E) could alleviate risks associated with seasonal rainfall variability and enhance reliability of yield of this crop. The objectives of this study were to quantify G x E x M interactions and identify best combinations of G and M for target maize production environments in Ethiopia. Ten genotypes, five each from early and medium maturity classes were evaluated at five planting densities, 2, 5, 6, 7 and 9 plants m −2 , across seven environments in 2013 and 2014 cropping seasons. Our study explored a range of morphological, phenological and physiological traits underpinning the yield of maize. Our results revealed that combining the appropriate G and M is more effective than relying on the choice of genotypes. The optimum plant densities identified in this study are higher than the plant densities currently used by farmers. Planting BH-546 and TH13321 at 7 plants m −2 substantially increased yield compared with other genotypes. For instance, yield for TH13321 was higher by 48% (3.7 t ha-1) at 7 plants m −2 in high yielding environments compared with BH-540, the most widely grown hybrid by farmers. This indicates the need for optimising G and M and using versatile genotypes to exploit variability in weather and input-use in the country. The genotypes substantially varied for their response to radiation use efficiency, rainwater productivity and leaf orientation value at high plant density. The least response to these traits observed for BH-540 highlights the need for a reassessment of current varietal and agronomic options for maize production in Ethiopia. Information from this study could be extended to sub-Saharan African countries that are similarly using low plant density.
High inter-seasonal rainfall variability presents the biggest risk for farmers to invest in best ... more High inter-seasonal rainfall variability presents the biggest risk for farmers to invest in best management practices in maize grown in much of Ethiopia. Optimising genotype (G) and management (M) of maize for different growing environments (E) could alleviate risks associated with seasonal rainfall variability and enhance reliability of production of this crop. In this study, we explored this possibility with the help of the APSIM maize model. The model was first calibrated and then tested on different sets of data for its ability to simulate phenology, dry matter and yield of six genotypes of differing maturity grown under rainfed conditions at four plant densities at four sites including Bako, Hawassa, Melkassa and Adamitulu in Ethiopia in 2013 and 2014. The model accurately predicted plant available soil water (NRMSE = 6%), days-to-flowering (NRMSE = 4%), days to maturity (NRMSE = 4%), leaf area index (NRMSE = 6%), biomass (NRMSE = 13%) and yield (NRMSE = 5%). The simulations revealed that increasing plant density increased water use efficiency of genotypes at all sites. The model in conjunction with site-specific soil properties and 33 years of daily weather data was then used to simulate changes in the water supply demand ratio to determine dominant drought patterns at each site which could be clustered into four major drought patterns. These drought patterns included low stress occurring in 55% of the seasons, mid-season occurring in 11% of the seasons, early terminal drought in 17% of the seasons, and late terminal drought 17% of the seasons. The frequencies of these drought patterns varied at different sites. These could also be manipulated by genotypes of different maturity and plant density resulting in different yield outcomes at each site. The study revealed significant scope for yield improvement by manipulating G and M, with larger effects in favourable seasons.
Maize is a staple food crop in eastern and southern Africa with significant contribution for food... more Maize is a staple food crop in eastern and southern Africa with significant contribution for food security of this vast region. Efforts to breed superior maize cultivars for the region are challenged by high genotype x environment interactions arising mainly due to variable soil moisture supply caused by high temporal and spatial variability in rainfall. Information on major drought patterns and their frequencies, which can assist in dealing with such interactions in the region, however, is not available. The objectives of this study were therefore to (i) identify major drought patterns and their frequencies, (ii) identify iso-environments based on the similarity of drought patterns and (iii) explore scope for yield improvement through optimising genotype and management in various drought patterns. We used the well validated APSIM model to characterise major drought patterns and their frequencies experienced by maize cropping systems in the target population of environments spread across six countries of the region including Ethiopia, Kenya, Tanzania, Malawi, Mozambique and Zimbabwe. The database used for the model simulations consisted of 35 locations, 17-86 years of daily climate records and three cultivars. The dynamic changes in water supply-demand ratio in each season was simulated against the thermal time for each cultivar across the 35 locations and clustering analysis was used to cluster the major drought patterns. The analysis identified four major drought patterns characterised by low-stress, mid-season drought, late terminal drought and early-terminal drought patterns, occurring at 46%, 11%, 22% and 21% of the years, respectively. The frequencies of these patterns varied in relation to locations, genotypes and management. Yield reduction of up to 80% was observed for early terminal drought compared with low-stress drought pattern. There was significant scope for yield improvement through manipulating genotype and management. These results have important implications for germplasm enhancement and deployment over similar environments in the region.
Chickpea (Cicer arietinum L.) has been traditionally grown in India but is a relatively new expor... more Chickpea (Cicer arietinum L.) has been traditionally grown in India but is a relatively new export crop in Australia where its cultivation is expanding into new areas. The objective of this study was to identify homoclimes (i.e. similar chickpea-growing environments) in the major chickpea-growing areas of the 2 countries, using the Agricultural Production Systems Simulator (APSIM) chickpea model. The model, which processes climatic, soil, and plant information on a daily time step, was first validated and then used to simulate flowering, maturity, and grain yield of Amethyst, a mid-season cultivar, and Barwon, a full-season cultivar, on low (100 mm), medium (150 mm), and high (190 mm) water-holding capacity soils, using historical climatic data of 67 Australian and 24 Indian locations. The mean of annual outputs of flowering, maturity, and grain yield of the 2 cultivars on 3 soils was then clustered using Ward’s hierarchical complete linkage clustering procedure. At a 90% level of s...
Australian Journal of Experimental Agriculture, 2007
Measurement or accurate simulation of soil temperature is important for improved understanding an... more Measurement or accurate simulation of soil temperature is important for improved understanding and management of peanuts (Arachis hypogaea L.), due to their geocarpic habit. A module of the Agricultural Production Systems Simulator Model (APSIM), APSIM-soiltemp, which uses input of ambient temperature, rainfall and solar radiation in conjunction with other APSIM modules, was evaluated for its ability to simulate surface 5 cm soil temperature in 35 peanut on-farm trials conducted between 2001 and 2005 in the Burnett region (25°36′S to 26°41′S, 151°39′E to 151°53′E). Soil temperature simulated by the APSIM-soiltemp module, from 30 days after sowing until maturity, closely matched the measured values (R2 ≥ 0.80) in the first three seasons (2001–04). However, a slightly poorer relationship (R2 = 0.55) between the observed and the simulated temperatures was observed in 2004–05, when the crop was severely water stressed. Nevertheless, over all the four seasons, which were characterised by...
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Papers by Yash Chauhan