Submitted to: BARC Poster Day
Publication Type: Abstract only
Publication Acceptance Date: 4/19/2012
Publication Date: N/A
Citation: Interpretive Summary:
Technical Abstract: Simulating root growth is critical to understand nutrient and water uptake dynamics of major crops, and to improve agricultural decision support tools for natural resource management. Plants invest more assimilated carbon into their root system when under stress in order to explore a greater soil volume for obtaining resources. Because roots grow below ground it is a laborious task to excavate them and to quantify their mass distribution experimentally. Nevertheless, a root growth model has to be tested against "real world" data. Potato (Solanum tuberosum L.) is an ideal crop to test and calibrate a root growth model because growth and yield are sensitive to drought and nutrient deficiencies starting at mild stress levels. Experimental data were modeled using the process level potato model SpudSim, developed in the Crop Systems and Global Change Laboratory of USDA-ARS in Beltsville, Maryland. The root module of SpudSim estimates root growth in two dimensions according to a diffusive scheme. Parameters controlling the direction of root growth are the diffusion coefficients in x- and z- direction, and a velocity term in z-direction (downwards). Carbon distribution between roots and shoot is estimated as a function of water status of the plant. A carbon partitioning routine calculates root growth correction factors for water and nutrient status of the soil, bulk density and temperature. The crop module is coupled to SWMS_2D which estimates water and solute transport in the soil. In its present version, SpudSim simulates solute transport and uptake by the roots for nitrogen in the form of nitrate. Experimental data consisted of potato above and below ground dry weights from a 2005 study conducted in our SPAR chambers. Six different water and nutrient treatment levels were utilized to evaluate the model results. At harvest, the above ground plant organs were collected separately and soil cores were taken. The roots in the cores were washed from the surrounding soil to determine their mass. Additionally, roots were traced at the middle and at the end of the growing season on front acrylic glass walls of the SPAR chambers, whose covers could be removed. The recently implemented diffusive root growth module could be calibrated using these experimental root data. Experimentally observed carbon allocation shifting towards the root system for stressed plants could be confirmed and quantified by modeling results.