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  • 1
    Electronic Resource
    Electronic Resource
    A comparative study on Striga hermonthica interaction with a sensitive and a tolerant sorghum cultivar (2000)
    Oxford UK : Blackwell Science Ltd
    Weed research 40 (2000), S. 0 
    Details
    ISSN: 1365-3180
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: In this study, the effects of Striga hermonthica (Del.) Benth. on a sensitive and a tolerant sorghum genotype were investigated, and the underlying tolerance mechanisms were distinguished. The sensitive sorghum cv. CK60-B and the tolerant sorghum landrace Tiemarifing were grown in pots with and without seed infestation. Both sorghum genotypes responded to infection by the parasite, but it was evident that CK60-B was more strongly affected than Tiemarifing. Sorghum plant height, final leaf number, green leaf area, kernel yield, number of kernels and 1000-kernel weight were significantly reduced by infection, which also had a marked effect on the phenological development of CK60-B; the majority of the plants remained vegetative and, in the remaining plants, flowering was delayed by about 2 weeks. No effect on the phenological development of Tiemarifing was observed. The tolerant landrace showed significantly lower and delayed emergence of S. hermonthica than the sensitive cultivar, and this could be explained by a delay in the onset of attachment. Significantly higher numbers of reproductive parasitic plants were found in the pots with the sensitive sorghum plants. It is concluded that differences in root architecture and the resulting early infection and higher S. hermonthica numbers are partly responsible for the stronger effects of the parasite on the sensitive cultivar.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3180.2000.00204.x
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  • 2
    Electronic Resource
    Electronic Resource
    An evaluation of four crop : weed competition models using a common data set (2003)
    Oxford, UK : Blackwell Science Ltd
    Weed research 43 (2003), S. 0 
    Details
    ISSN: 1365-3180
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary To date, several crop : weed competition models have been developed. Developers of the various models were invited to compare model performance using a common data set. The data set consisted of wheat and Lolium rigidum grown in monoculture and mixtures under dryland and irrigated conditions. Results from four crop : weed competition models are presented: almanac, apsim, cropsim and intercom. For all models, deviations between observed and predicted values for monoculture wheat were only slightly lower than for wheat grown in competition with L. rigidum, even though the workshop participants had access to monoculture data while parameterizing models. Much of the error in simulating competition outcome was associated with difficulties in accurately simulating growth of individual species. Relatively simple competition algorithms were capable of accounting for the majority of the competition response. Increasing model complexity did not appear to dramatically improve model accuracy. Comparison of specific competition processes, such as radiation interception, was very difficult since the effects of these processes within each model could not be isolated. Algorithms for competition processes need to be modularised in such a way that exchange, evaluation and comparison across models is facilitated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3180.2003.00323.x
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  • 3
    Electronic Resource
    Electronic Resource
    The influence of nitrogen supply on the ability of wheat and potato to suppress Stellaria media growth and reproduction (2002)
    Oxford, UK : Blackwell Science Ltd
    Weed research 42 (2002), S. 0 
    Details
    ISSN: 1365-3180
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary This paper tests the hypothesis that increased soil nitrogen supply reduces the growth of late-emerging weeds in wheat and potato by enhancing canopy leaf area development and thereby reducing the availability of light for weed growth. Two series of experiments were conducted: one in spring wheat (1997, 1999) with sown Stellaria media and one in potato (1998, 1999) with naturally emerged weeds, including S. media. For each crop, two cultivars were grown at three levels of nitrogen supply. In wheat, as in a monoculture of S. media, total dry weight and seed number of the weed increased with soil nitrogen supply, whereas in potato the opposite was found. Increased soil nitrogen supply increased the nitrogen uptake of S. media in wheat, despite the reduced light availability, indicating that S. media in wheat was limited by nitrogen. In potato, on the other hand, growth of S. media was limited by light availability, which decreased with increased soil nitrogen supply. We conclude that the differences in response of S. media in wheat and potato to additional nitrogen supply are attributable to the dual influence of soil nitrogen supply on light and nitrogen availability, which are mediated by the crops.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3180.2002.00303.x
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  • 4
    Electronic Resource
    Electronic Resource
    Effect on leaf photosynthetic rate by leaf blast for rice cultivars with different types and levels of resistance (1992)
    Springer
    Euphytica 66 (1992), S. 81-87 
    Details
    ISSN: 1573-5060
    Keywords: leaf blast ; Oryza sativa ; photosynthesis ; Pyricularia oryzae ; rice ; tolerance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The effect of an inoculation with Pyricularia oryzae (isolate P06-6) on net leaf photosynthetic rate of rice (Oryza sativa) was studied with four cultivars. Measurements were taken on the sixth leaf of the main culm of plants in the early tillering stage. On cultivars CO39, IR50 and IR64 a susceptible infection type developed, but a clear difference in relative infection efficiency of the cultivars was observed. The highest number of lesions developed on leaves of CO39, whereas the lowest number was found on leaves of IR64. For all three cultivars the effect of a single lesion on the reduction in net leaf photosynthetic rate was found to be equal to a reduction in leaf area of three times the area occupied by the visible lesion. On IR68, a cultivar with complete resistance, brown specks of pinpoint size appeared without any effect on net leaf photosynthetic rate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00023511
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  • 5
    Electronic Resource
    Electronic Resource
    Effects of leaf blast on photosynthesis of rice. 1. Leaf photosynthesis (1993)
    Springer
    European journal of plant pathology 99 (1993), S. 197-203 
    Details
    ISSN: 1573-8469
    Keywords: Pyricularia ozyzae ; Oryza sativa ; respiration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The effect ofPyricularia oryzae, the causal organism of leaf blast in rice, on photosynthesis characteristics of rice leaves was measured in two greenhouse experiments. Leaf blast reduced photosynthesis not only through a reduction in green leaf area, but also through an effect on photosynthesis of green leaf tissue surrounding the lesions. The assimilation rate at light saturation (P max ) was more affected than the initial light use efficiency (∈). Dark respiration (R d ) increased as a result of infection. The experimental data were used to derive relations between leaf blast severity andP max , ∈ andR d .
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01974664
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  • 6
    Electronic Resource
    Electronic Resource
    Effects of leaf blast on photosynthesis of rice 2. Canopy photosynthesis (1993)
    Springer
    European journal of plant pathology 99 (1993), S. 205-217 
    Details
    ISSN: 1573-8469
    Keywords: Pyricularia oryza ; Oryza sativa ; simulation model ; respiration ; vertical distribution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The effect ofPyricularia oryzae, the causal organism of leaf blast in rice, on photosynthetic rate of a rice crop was determined with mobile equipment in the field. Canopy CO2 exchanges rate (CER) was significantly reduced in plots inoculated withP. oryzae. The experimentally obtained data were used to evaluate the performance of a model for the effects of leaf blast on canopy photosynthesis. The model comprised photosynthesis and respiration routines of a mechanistic crop growth model, extended with submodels for effects of leaf blast on both processes. Canopy photosynthesis and the effect of leaf blast on CER were accurately simulated with the model. Analysis showed that the reduction in canopy photosynthesis was mainly due to an adverse effect of lesions on leaf photosynthetic rate and to shading by dead leaf are resulting from disease induced senescence. A sensitivity analysis demonstrated the importance of the vertical distribution of the disease in the canopy. This implies that disease monitoring for crop loss assessment should consider vertical disease distribution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01974665
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  • 7
    Electronic Resource
    Electronic Resource
    Effects of leaf blast on growth and production of a rice crop (1993)
    Springer
    European journal of plant pathology 99 (1993), S. 323-334 
    Details
    ISSN: 1573-8469
    Keywords: Pyricularia oryzae ; Oryza sativa ; crop loss
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Rice crops grown under irrigated conditions were inoculated withPyricularia oryzae during early growth stages to study the effect of leaf blast on yield formation. The inoculations led to severe epidemics of leaf blast around maximum tillering, characterized by the presence of typical blast lesions and an accelerated senescence of heavily infested leaf tissue. Leaf blast led to a prolonged tillering and a delay in flowering and maturity. Crop growth rate and leaf area formation declined sharply during establishment of the disease and continued to be reduced till maturity. This resulted in a marked reduction of total dry matter production and grain yield. Dry matter distribution was not affected. Leaf blast reduced spikelet number, 1000 grain weight, and the fraction filled grains. From this last observation it was concluded that the reduction in grain yield was exclusively source determined. Nitrogen uptake of the inoculated crops before flowering was reduced compared to the N uptake of the control crop, but shoot N content of the inoculated crops at flowering was higher. Uptake of nitrogen after flowering was negligible in both healthy and inoculated crops. Redistribution from vegetative tissue was therefore the main source of N for grain growth. The higher N content of the shoot organs in the inoculated crops during ripening led to the conclusion that the reduced N uptake was not responsible for the yield reduction observed. Consequently, the reduction in grain yield was solely determined by a reduced carbohydrate supply.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01974313
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  • 8
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    Cultivar Weed‐Competitiveness in Aerobic Rice: Heritability, Correlated Traits, and the Potential for Indirect Selection in Weed‐Free Environments (2006)
    Wiley
    Details
    Publication Date: 2006-01-01
    Print ISSN: 0011-183X
    Electronic ISSN: 1435-0653
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Wiley
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  • 9
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    Biochar increases plant available water in a sandy soil under an aerobic rice cropping system (2014)
    Copernicus
    Details
    Publication Date: 2014-03-18
    Description: The main objective of this study was to assess the impact of biochar rate (0, 8, 16 and 32 t ha−1) on the water retention capacity (WRC) of a sandy Dystric Plinthosol. The applied biochar was a by-product of slow pyrolysis (∼450 °C) of eucalyptus wood, milled to pass through a 2000 μm sieve that resulted in a material with an intrinsic porosity ≤10 μm and a specific surface area of ∼3.2 m2 g−1. The biochar was incorporated into the top 15 cm of the soil under an aerobic rice system. Our study focused on both the effects on WRC and rice yields at 2 and 3 years after application. Undisturbed soil samples were collected from 16 plots in two soil layers (5–10 and 15–20 cm). Soil water retention curves were modelled using a nonlinear mixed model which appropriately accounts for uncertainties inherent of spatial variability and repeated measurements taken within a specific soil sample. We found an increase in plant available water in the upper soil layer proportional to the rate of biochar, with about 0.8% for each t ha−1 of biochar amendment at 2 and 3 years after application. The impact of biochar on soil WRC was most likely related to an increase in overall porosity of the sandy soil, which was evident from an increase in saturated soil moisture and macro porosity with 0.5% and 1.6% for each t ha−1 of biochar applied, respectively. The increment in soil WRC did not translate into an increase in rice yield, essentially because in both seasons the amount of rainfall during critical period for rice production exceeded 650 mm. The use of biochar as a soil amendment can be a worthy strategy to guarantee yield stability under water limited conditions. Our findings raise the importance of assessing the feasibility of very high application rates of biochar and the inclusion of a detailed analysis of its physical and chemical properties as part of future investigations.
    Electronic ISSN: 1869-9537
    Topics: Geosciences
    Published by Copernicus on behalf of European Geosciences Union.
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  • 10
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    Biochar increases plant-available water in a sandy loam soil under an aerobic rice crop system (2014)
    Copernicus
    Details
    Publication Date: 2014-09-03
    Description: The main objective of this study was to assess the impact of biochar rate (0, 8, 16 and 32 Mg ha−1) on the water retention capacity (WRC) of a sandy loam Dystric Plinthosol. The applied biochar was a by-product of slow pyrolysis (∼450 °C) of eucalyptus wood, milled to pass through a 2000 μm sieve that resulted in a material with an intrinsic porosity ≤10 μm and a specific surface area of ∼3.2 m2 g−1. The biochar was incorporated into the top 15 cm of the soil under an aerobic rice system. Our study focused on both the effects on WRC and rice yields 2 and 3 years after its application. Undisturbed soil samples were collected from 16 plots in two soil layers (5–10 and 15–20 cm). Soil water retention curves were modelled using a nonlinear mixed model which appropriately accounts for uncertainties inherent of spatial variability and repeated measurements taken within a specific soil sample. We found an increase in plant-available water in the upper soil layer proportional to the rate of biochar, with about 0.8% for each Mg ha−1 biochar amendment 2 and 3 years after its application. The impact of biochar on soil WRC was most likely related to an effect in overall porosity of the sandy loam soil, which was evident from an increase in saturated soil moisture and macro porosity with 0.5 and 1.6% for each Mg ha−1 of biochar applied, respectively. The increment in soil WRC did not translate into an increase in rice yield, essentially because in both seasons the amount of rainfall during the critical period for rice production exceeded 650 mm. The use of biochar as a soil amendment can be a worthy strategy to guarantee yield stability under short-term water-limited conditions. Our findings raise the importance of assessing the feasibility of very high application rates of biochar and the inclusion of a detailed analysis of its physical and chemical properties as part of future investigations.
    Print ISSN: 1869-9510
    Electronic ISSN: 1869-9529
    Topics: Geosciences
    Published by Copernicus on behalf of European Geosciences Union.
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