The Impact of Irrigation Scheduling on Peanut Growth and Development.

Computer crop simulation models have the potential to be an important aid for irrigation scheduling. In addition, they can be used to help understand the impact of water stress on plant growth and development as the models integrate the soil-plant-atmosphere complex. The objectives of this study were to determine the impact of different irrigation scheduling regimes on peanut growth and development and to determine the relation between the simulated water stress coefficients and yield. Two experiments were conducted in four rainout shelters, located at the Griffin Campus of The University of Georgia, during 2006 and 2007. The CSM-CROPGRO-Peanut model was used to define the irrigation treatments by estimating the timing of irrigation and the amount of water to apply. The irrigation event was triggered when the actual soil water content in the effective root zone dropped below a specific threshold of the available water content (AWC) and irrigation was applied until the soil water reached 100% of AWC. The irrigation treatments corresponded to 30%, 40%, 60% and 90% of the irrigation threshold (IT). The soil water content was monitored with Time-Domain-Reflectometry (TDR) probes and with a soil profile probe (PR2/6, Delta-T Devices, Ltd.). Growth analyses were conducted approximately every 18 days. Two water stress coefficients related to growth and photosynthesis, as determined by the CSM-CROPGRO-Peanut model, were analyzed to identify their relation with the observed and simulated yield. The results indicated that the simulated and observed peanut grain yield were in close agreement with the amount of water that was applied. There was an inverse relation between the simulated total cumulative water stress coefficients for photosynthesis and the simulated grain yield (r²=0.95). Similar results were obtained when analyzing the simulated total cumulative water stress index on growth versus simulated grain yield (r²=0.96). Further studies will focus on the correlation of cumulative water stress indices of different growth stages and associated yield.