Lili Mao

Modelling the structural response of cotton plants to mepiquat chloride and population density

BACKGROUND AND AIMS Cotton (Gossypium hirsutum) has indeterminate growth. The growth regulator mepiquat chloride (MC) is used worldwide to restrict vegetative growth and promote boll formation and yield. The effects of MC are modulated by complex interactions with growing conditions (nutrients, weather) and plant population density, and as a result the effects on plant form are not fully understood and are difficult to predict. The use of MC is thus hard to optimize. METHODS To explore crop responses to plant density and MC, a functional-structural plant model (FSPM) for cotton (named CottonXL) was designed. The model was calibrated using 1 years field data, and validated by using two additional years of detailed experimental data on the effects of MC and plant density in stands of pure cotton and in intercrops of cotton with wheat. CottonXL simulates development of leaf and fruits (square, flower and boll), plant height and branching. Crop development is driven by thermal time, population density, MC application, and topping of the main stem and branches. KEY RESULTS Validation of the model showed good correspondence between simulated and observed values for leaf area index with an overall root-mean-square error of 0·50 m(2) m(-2), and with an overall prediction error of less than 10% for number of bolls, plant height, number of fruit branches and number of phytomers. Canopy structure became more compact with the decrease of leaf area index and internode length due to the application of MC. Moreover, MC did not have a substantial effect on boll density but increased lint yield at higher densities. CONCLUSIONS The model satisfactorily represents the effects of agronomic measures on cotton plant structure. It can be used to identify optimal agronomic management of cotton to achieve optimal plant structure for maximum yield under varying environmental conditions.

Resource use efficiency, ecological intensification and sustainability of intercropping systems

Abstract The rapidly growing demand for food, feed and fuel requires further improvements of land and water management, crop productivity and resource-use efficiencies. Combined field experimentation and crop growth modelling during the past five decades made a great leap forward in the understanding of factors that determine actual and potential yields of monocrops. The research field of production ecology developed concepts to integrate biological and biophysical processes with the aim to explore crop growth potential in contrasting environments. To understand the potential of more complex systems (multi-crop-ping and intercropping) we need an agro-ecosystem approach that integrates knowledge derived from various disciplines: agronomy, crop physiology, crop ecology, and environmental sciences (soil, water and climate). Adaptation of cropping systems to climate change and a better tolerance to biotic and abiotic stresses by genetic improvement and by managing diverse cropping systems in a sustainable way will be of key importance in food security. To accelerate sustainable intensification of agricultural production, it is required to develop intercropping systems that are highly productive and stable under conditions with abiotic constraints (water, nutrients and weather). Strategies to achieve sustainable intensification include developing tools to evaluate crop growth potential under more extreme climatic conditions and introducing new crops and cropping systems that are more productive and robust under conditions with abiotic stress. This paper presents some examples of sustainable intensification management of intercropping systems that proved to be tolerant to extreme climate conditions.

Predicting the effects of environment and management on cotton fibre growth and quality: a functional–structural plant modelling approach

Fruit quality and more specifically quality of the fiber in the fruit of cotton, depends on interactions between fruit position in the plant architecture, temperature and agronomical practices, such as sowing time, mulching with plastic film, and topping of the plants main stem and branches. A functional and structural cotton model CottonXL for fiber quality (strength, length and micronaire) was implemented at the level of each individual fruit in relation to thermal time for optimizing cotton fiber quality by matching cotton management to the environment. The model may be used to address climate and land use change scenarios.