The interactions between genotype,management and environment in regional crop modelling

Biophysical models to simulate crop yield are increasingly applied in regional climate impact assessments. When performing large-area simulations, there is often a paucity of data to spatially represent changes in genotype (G) and management (M) across different environments (E). The importance of this uncertainty source in simulation results is currently unclear. In this study, we used a variance-based sensitivity analysis to quantify the relative contribution of maize hybrid (i.e. G) and sowing date (i.e. M) to the variability in biomass yield (Y_T, total above-ground biomass) and harvest index (HI, fraction of grain in total yield) of irrigated silage maize, across the extent of arable lands in New Zealand (i.e. E). Using a locally calibrated crop model (APSIM-maize), 25 G x M scenarios were simulated at a 5 arc minute resolution (∼5 km grid cell) using 30 years of historical weather data. Our results indicate that the impact of limited knowledge on G and M parameters depends on E and differs between model outputs. Specifically, the sensitivity of Y_T and HI to genotype and sowing date combinations showed different patterns across locations. The absolute impact of G and M factors was consistently greater in the colder southern regions of New Zealand. However, the relative share of total variability explained by each factor, the sensitivity index (S_i), showed distinct spatial patterns for the two output variables. The Y_T was more sensitive than HI in the warmer northern regions where absolute variability was the smallest. These patterns were characterised by a systematic response of S_i to environmental drivers. For example, the sensitivity of Y_T and HI to hybrid maturity consistently increased with temperature. For the irrigated conditions assumed in our study, inter-annual weather conditions explained a higher share of total variability in the southern colder regions. Our results suggest that the development of methods and datasets to more accurately represent spatio-temporal G and M variability can reduce uncertainty in regional modelling assessments at different degrees, depending on prevailing environmental conditions and the output variable of interest.     

Evaluation of pixel- and object-based approaches for mapping wild oat (Avena sterilis) weed patches in wheat fields using QuickBird imagery for site-specific management

This paper compares of pixel- and object-based techniques for mapping wild oat weed patches in wheat fields using multi-spectral QuickBird satellite imagery for site-specific weed management. The research was conducted at two levels: (1) at the field level, on 11 and 15 individual infested wheat fields in 2006 and 2008, respectively, and (2) on a broader level, by analysing the entire 2006 and 2008 images. To evaluate the wild oat patches mapping at the field level, both pixel- and object-based image analyses were tested with six classification algorithms: Parallelepipeds (P), Mahalanobis Distance (MD), Maximum Likelihood (ML), Spectral Angle Mapper (SAM), Support Vector Machine (SVM) and Decision Tree (DT). The results showed that weed patches could be accurately detected with both analyses obtaining global accuracies between 80% and 99% for most of the fields. The MD and SVM classifiers were the most accurate for both the pixel- and object-based images from 2006 and 2008, respectively. In the broad-scale analysis, all of the wheat fields were identified in the imagery using a multiresolution hierarchical segmentation based on two scales. The first segmentation scale was classified using the MD and ML algorithms to discriminate wheat fields from other land uses. Accuracies greater than 85% were obtained for MD and 88% for ML for both imagery. A hierarchical analysis was then performed with the second segmentation scale, increasing the accuracies to 93% and 91% for 2006 and 2008 imagery, respectively. Finally, based on the most accurate results obtained in the field-level study, pixel-based classifications using the MD, ML and SVM algorithms were applied to the wheat fields identified. The results of these broad-level analyses showed that wild oat patches were accurately discriminated in all the wheat fields present in the entire images with accuracies greater than 91% for all the classifiers tested.     

江淮下游不同播期对稻–麦周年作物产量、品质及温光资源利用的影响

对江淮下游稻麦两熟高产优质种植模式周年气候资源分配和利用特征的探究,可以为当地机插水稻–小麦周年产量和气候资源利用效率的提高提供一定的理论依据。在泰州兴化市,水稻季以迟熟中粳南粳9108和中熟中粳连粳11为材料,设置5月22日(R-Ⅰ)、5月29日(R-Ⅱ)和6月5日(R-Ⅲ) 3个播期,小麦季以冬小麦宁麦13为材料,设置11月5日(W-Ⅰ)、11月15日(W-Ⅱ)和11月25日(W-Ⅲ) 3个播期,分析了不同播期下机插水稻–小麦周年高产优质形成与稻季、麦季资源分配特征。结果表明,水稻季,随着播期推迟,迟熟中粳南粳9108产量、温光资源量及其生产效率均显著下降,中熟中粳连粳11温光资源量呈下降趋势,但产量及温光利用率呈先升后降趋势,各播期迟熟中粳产量均高于中熟中粳。小麦季,产量、温光资源量及其生产效率均随播期推迟有不同程度降低。从周年生产看,周年稻麦产量随两季作物播期的推迟显著降低,其中迟熟中粳南粳9108播期R-Ⅰ与小麦播期W-Ⅰ组合在所有处理中产量最高。水稻产量占周年产量比例最高为62.99%,最低为55.86%。两季间积温分配率水稻季最高为68.38%,小麦季最高为34.14%。...     

On-farm evaluation of integrated weed management tools for maize production in three different agro-environments in Europe: Agronomic efficacy,herbicide use reduction,and economic sustainability

The development and implementation of integrated weed management (IWM) strategies that provide good weed control while reducing dependence on herbicides, and preferably without having side effects on the overall system economic performance, is still a challenge that has to be met. In 2011 and 2012, nine on-farm experiments (i.e., real field conditions on commercial farms, with natural weed flora) were conducted in three important European maize producing regions-countries, which represent the range of climatic and edaphic conditions in Europe, to evaluate the efficacy of different locally selected IWM tools for direct weed control in maize vs. the conventional approach (CON) followed by the farms. The IWM tools tested were: (1) early post-emergence herbicide band application combined with hoeing followed by a second hoeing in Southern Germany, (2) early post-emergence herbicide broadcast application when indicated by a predictive model of weed emergence after performing one scouting in the field to supply data for the model, followed by hoeing in Northern Italy, and (3) tine harrowing at 2–3rd leaf stage of maize and low dose of post-emergence herbicide in Slovenia. Results showed that the IWM tools tested in the different countries: (1) provided sufficient weed control without any significant differences in yields, (2) greatly reduced maize reliance on herbicides, and (3) IWM implementation was economically sustainable as no significant differences in gross margin were observed in any country compared to CON.     

Growth,physiological, and biochemical responses in relation to salinity tolerance for In Vitro selection in oil seed crop Guizotia abyssinica Cass.

The calli cultures of Guizotia abyssinica (niger) cultivars IGP 76 and GA 10 were exposed to different levels of salt treatments (0, 30, 60, and 90 mM NaCl), in order to evaluate growth, physiological, and biochemical responses. A significant decrease in relative growth rate and tissue water content of GA 10 calli than IGP 76 under salt-stress conditions was associated with higher sodium ion accumulation. Osmotic adjustment revealed by the osmolytes (proline, glycine betaine, and total soluble sugars) accumulation was significantly higher in IGP 76 salt-stressed calli as compared to GA 10. The sustained growth and better survival of IGP 76 calli was correlated with lower malondialdehyde content and increased superoxide dismutase, ascorbate peroxidase, and catalase activities and higher α-tocopherol content in comparison to GA 10. The higher osmolytes accumulation and presence of better antioxidant system suggested superior adaptation of IGP 76 calli on salt-containing medium for prolonged periods in comparison to GA 10. The regeneration frequency, organogenesis, and acclimatization response of the plants derived from salt-adapted calli was comparatively lower than the plants derived from control calli of IGP 76. The growth, physiological, and biochemical characterization of the salt-tolerant regenerated plants exposed to stepwise long-term 90 mM NaCl treatment revealed no significant changes in comparison to the control. Thus, our results suggests the development of an efficient protocol for in vitro selection and production of salt-tolerant plants in self-incompatible crop, niger, and an alternative to traditional breeding programs to increase the abiotic stress tolerance.     

Simulation of growth and development processes of spring wheat in response to CO2 and ozone for different sites and years in Europe using mechanistic crop simulation models

The response of crop growth and yield to CO₂ and ozone is known to depend on climatic conditions and is difficult to quantify due to the complexity of the processes involved. Two modified mechanistic crop simulation models (AFRCWHEAT2-O3 and LINTULCC), which differ in the levels of mechanistic detail, were used to simulate the effects of CO₂ (ambient, ambient ×2) and ozone (ambient, ambient ×1.5) on growth and developmental processes of spring wheat in response to climatic conditions. Simulations were analysed using data from the ESPACE-wheat project in which spring wheat cv. Minaret was grown in open-top chambers at nine sites throughout Europe and for up to 3 years at each site.

Both models closely predicted phenological development and the average measured biomass at maturity. However, intermediate growth variables such as biomass and leaf area index (LAI) at anthesis, seasonal accumulated photosynthetically active radiation intercepted by the crop (ΣIPAR), the average seasonal light use efficiency (LUE) and the light saturated rate of flag leaf photosynthesis (A_sat) were predicted differently and less accurately by the two models. The effect of CO₂ on the final biomass was underestimated by AFRCWHEAT2-O3 due to its poor simulation of the effect of CO₂ on tillering, and LAI.LINTULCC overestimated the response of biomass production to changes in CO₂ level due to an overprediction of the effect of CO₂ on LUE. The measured effect of ozone exposure on final biomass was predicted closely by the two models. The models also simulated the observed interactive effect of CO₂ and ozone on biomass production. However, the effects of ozone on LAI, ΣIPAR and A_sat were simulated differently by the models and less accurately with LINTULCC for the ozone effects on LAI and ΣIPAR. Predictions of the variation between sites and years of growth and development parameters and of their responses to CO₂ and ozone were poor for both AFRCWHEAT2-O3 and LINTULCC. It was concluded that other factors than those considered in the models such as chamber design and soil properties may have affected the growth and development of cv. Minaret. An analysis of the relationships between growth parameters calculated from the simulations supported this conclusion. In order to apply models for global change impact assessment studies, the difficulties in simulating biomass production in response to CO₂ need to be considered. We suggest that the simulation of leaf area dynamics deserves particular attention in this regard.     

What does foreign aid for education contribute to the maintenance of indigenous knowledge in Laos,Thailand and Vietnam?

These notes are based on observations conducted over seventeen years, including visits to projects, both structured and open ended interviews with participants and, more recently, a systematic review of reports prepared between 1991 and 1995. Results show that the principal thrust of all foreign aid projects which targeted indigenous people as preferred recipients were designed to provide access to state schooling, an education conducted in the national language and dominated by curricula objectives originating in the capital city. This is not what the people want. The preoccupation of state authorities with nation building and teaching skills that meet urban and industrial needs rather than the rural and agricultural priorities of indigenous people has contributed to the latters growing sense of alienation and eroded their sense of identity.