Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/1/1996
Publication Date: N/A
Interpretive Summary: Profitable wheat farming depends upon informed management of soil, water, and nutrient resources by any farm operator. Investigations of production problems by farm operators or research scientists requires knowledge of expected growth and growth stages of the wheat crop. Grain yields can be improved if farmers time their management operations to provide greatest possible benefit to the wheat plant. To do so, farmers and researchers must be able to anticipate and then recognize wheat growth stages. The wheat growth model MODWht3 provides a computerized tool that will simulate day to day wheat growth from planting to harvest. Using local temperature, rainfall, planting and sunshine data from any wheat producing region, the model provides estimates of growth and expected dates of various growth stages. Such information allows more precise timing and effective application of growth stage dependent herbicides, nutrients, and where available, supplemental water.
Technical Abstract: Crop growth simulations are needed to assist in organizing our knowledge of plant response to the environment for the purpose of assisting growers in management decisions, predicting impacts of land use decisions, and predicting the consequences of probable climatic variation. This paper describes the combination and calibration, where necessary, of the models required to produce a simulation of the seasonal development and growth of winter wheat. The simulation provides appearance time and size estimates for each above-ground plant part (leaves, stems, spikes, and kernels), length and mass of roots with depth, time of occurrence of phenological events (germination, emergence, tillering, single ridge, double ridge, jointing boot, heading, anthesis, soft dough, mature, harvest ripe), rate and amount of water evaporated and transpired, uptake of nitrogen from the soil profile and estimates of daily net photosynthesis. Strengths of the simulation include the prediction of dates for all crop phenological stages, and the generation of size estimates for all plant parts on a daily basis throughout the growing season so that comparisons can be made with almost any observed field data. Weaknesses include the lack of known ranges of parameter values that are characteristic of different cultivars, a simplistic soil water budget, and limitations in specifying nutrient distribution among plant organs. No weed, pathogen or insect models are incorporated; however the program that implements the simulation is specifically designed to be easily modified, so pest models could be added.