1a. Objectives (from AD-416)
The overall objective is to refine and improve existing simulation models for corn and potato by developing new, and improving existing functional relationships between physiological processes and nutrients in the soil and plant tissues. Results of this research will be used to address existing knowledge gaps in the models. The modified models will be evaluated by testing simulated responses at plant component and whole plant levels. The specific sub-objectives are to improve simulation of the above- and below-ground potato and corn processes in the areas of: (1) water and nutrient stress effects on growth, development, morphology, and yield, and (2) response of root growth and activity (water and nutrient uptake) to soil nutrients (N, P and K), and water. The model and new components will be evaluated using experimental data. The potato and corn models, along with a rye cover crop model and existing models for soybean and corn, will then be used for assessment of the environmental consequences of agricultural management practices on carbon sequestration and nutrient balances. These practices include fertilizer applications, rotations, and cover crops.
1b. Approach (from AD-416)
Mechanistic models for soybean (GLYCIM), cotton (GOSSYM), corn (MAIZSIM) and potato (SPUDSIM) have been developed in previous projects by this group. The proposed research will broaden the capabilities of the corn and potato models by utilizing data from experiments carried out in unique, state-of-the-art sun-lit growth chambers and field plots. Short and long term experiments will be employed to test hypotheses and develop algorithms for plant processes to be used in the computer models. Data collected by collaborators will be used to test and evaluate the models. A simple Rye model will be developed to simulate a cover crop during the fall-winter season. A computer graphical user interface will be developed using components from the existing software program, GUICS, to allow a user to simulate long term crop rotations over multiple growing seasons. Advanced data management capabilities will be added to the interface to help with interpretation and management of input and output data. Tools for weather generation and estimation of soil hydraulic properties will be added to the interface to provide a wide range of environmental conditions for assessment. All crop models will be used within the new interface to assess the environmental and economic impacts of climate change on carbon sequestration, and nitrogen and water balances for relevant production systems.
3. Progress Report
Experimental results for effects of phosphorus and carbon dioxide enrichment on potato production were analyzed and submitted for publication. The potato model SPUDSIM was modified to include effects of water stress on stomatal conductance, leaf expansion rate, carbon allocation and to predict nitrogen uptake. Validation data for the potato and corn models from the Pacific Northwest and the Eastern seaboard states were established. Research methodologies to link the potato model to such data, including climate and soils, using spatial databases, were developed. Experiments to quantify the relationship between photosynthesis and water stress, and abscissic acid content in corn and potato were carried out. Data to parameterize photosynthesis and leaf growth equations for the corn model were developed. Field experiments were conducted during 2001-06 in Mississippi to collect plant growth data of six genetically modified (GM) cultivars which are popular in U.S. Cotton belt. GOSSYM, a cotton simulation model was calibrated and validated using field data to develop variety files for GM cultivars. Results of simulation revealed that GOSSYM was capable of simulating growth and development of GM cultivars. Corn yield, growth, meteorological and soils data were collected from a drought study carried out at Ft. Collins, CO. MAIZSIM files were generated from these data and simulations run to evaluate the ability of MAIZSIM to simulate corn yields under drought conditions. An experiment to study rye growth and development as a function of air temperature and planting density was carried out in the outdoor growth chambers over the winter of 2010-2011. The data will be used to test a rye model and to evaluate the effects of temperature and plant density on the ability of rye to scavenge nitrogen when used as a cover crop. An experiment to quantify effects of phosphorus deficiency on cotton growth and yield under ambient and elevated CO2 was carried out in indoor growth chambers. Results of the research will be used to improve the cotton model GOSSYM. Continued work towards implementing an interface for combining the crop models in the GUICS series (SPUDSIM, MAIZSIM) with the geographic information system (GIS) through ArcGIS to perform regional-scale analyses using various spatial datasets (weather, soil, management, and land use). Much of the interface has been designed and preliminary model simulations completed. The objective is to assess food security issues in Maine and the Northeastern United States. Continued work with the NRCS to evaluate the APEX model for use in the CEAP program. The progress is fully described in the project report for project 1265-61660-006-01R Conservation Effects Assessment Project. Continued collaboration with scientists at the Agricultural Systems Research Laboratory in Ft. Collins, CO for the corn model evaluation and implementation. Also continued an ongoing collaboration with the Vegetable Crops Research Unit in Prosser, WA to validate and test the potato model.
1. Corn water use efficiency increases under elevated CO2. Water availability for agriculture is expected to decline and CO2 increase in the future. Thus it is important to understand how plants grown under elevated CO2 will respond to water stress. We investigated the relationship between plant growth and water use by a corn crop in sun-lit growth chambers with soilbins at two CO2 concentrations. Soil water contents observed under elevated CO2 were higher than those grown under ambient CO2 concentrations even though less irrigation water was applied. The corn grown under elevated CO2 used up to 20% less water than corn grown under ambient CO2 levels. This information will be of use to growers and agricultural policy makers.
2. In growth chamber research, potato plants produced the same amount of growth independent of the number of stems under both elevated and ambient CO2. When growing potato, the production of numerous stems often complicates data collection for scientists who work with growth chambers and green house managers. Plants thinned to one stem per plant gave the same biomass and total leaf area per pot as plants with multiple stems. This was related to the ability of potato to continue to put on new branches and leaves throughout the growing season. These results serve to validate some of our research methodology in growth chambers and will be of use to greenhouse managers and scientists who do work in growth chambers.
3. The Cotton model GOSSYM has been validated for use with genetically modified (GM) cotton. In recent years, the use of GM cultivars of cotton has increased globally and in the U.S. Field experiments were conducted to collect plant growth data of six GM cultivars which are popular in U.S. Cotton belt during 2001-06 in Mississippi. GOSSYM, a cotton simulation model was calibrated and validated using field data to develop variety files for GM cultivars. Results of simulation revealed that GOSSYM was capable of simulating growth and development of GM cultivars. Variety files developed in this study will be beneficial to government agencies, researchers and consultants for various purposes.Chun, J.A., Wang, Q., Timlin, D.J., Fleisher, D.H., Reddy, V. 2011. Effect of elevated carbon dioxide and water stress on gas exchange and water use efficiency in corn. Agricultural and Forest Meteorology. 151:378-384.