Parametrization of germination and phenology submodels of APSIM-Annual Ryegrass for modelling annual ryegrass (Lolium multiflorum L.)

• Grant number: 23/07499-2
• Support Opportunities: Scholarships abroad - Research Internship - Doctorate
• Start date: September 19, 2023
• End date: September 04, 2024
• Field of knowledge: Agronomical Sciences - Animal Husbandry - Pastures and Forage Crops
• Principal Investigator: Patricia Menezes Santos
• Grantee: Felipe Luiz Chiamulera Deifeld
• Supervisor: Mariana Pares Andreucci
• Host Institution: Escola Superior de Agricultura Luiz de Queiroz (ESALQ). Universidade de São Paulo (USP). Piracicaba , SP, Brazil
• Institution abroad: Lincoln University, New Zealand
• Associated to the scholarship: 22/01766-6 - Parameterization of a model to simulate the productivity of Lolium multiflores L. and development of a test protocol for alternative technologies to cope with forage voids., BP.DR

Abstract

Pasture production simulation models are tools that can assist in decision-making, in simulating production, in research on crop management and genetic improvement, among others. Despite of the importance of temperate forage grasses for the production of meat and milk in Brazil, especially in the South region, little research was carried out on mathematical modelling of these species growth and production. Therefore, the objective of this project is to parameterize two submodels of the APSIM-Annual Ryegrass: germination and phenology. For this, data obtained from two experiments will be used, which are: i) cardinal germination temperature, in which four annual ryegrass cultivars were tested at different temperatures, and the percentage of germinated seeds was quantified; and ii) phenological development, in which a cultivar was sown over a year, with data being collected on emergence speed, Haun Stage, Zadock's Growth Stage and tillering. Models will be fitted to germination rates to quantify the influence of temperature on the development rate of each cultivar and thus obtain the basal, optimum and top temperatures. The cardinal temperatures will be used to quantify the daily thermal time for germination of each cultivar, based on a model, according to Olsen, McMahon and Hammer (1993). Emergence speed data will be analyzed to obtain the time needed to reach 50% emergence in the field, based on the final count of emerged seedlings (100%). The phyllochron will be calculated by fitting a regression of the cumulative number of fully expanded leaves as a function of thermal time for each plot. The photoperiod will be calculated using astronomical equations, in a three-step process for each day of the year, according to Weir et al. (1984), based on twilight when the sun is 6º below the horizon line. (AU)