ESTIMATING POTATO-TUBER YIELD IN A SUBTROPICAL ENVIRONMENT WITH SIMPLE RADIATION-BASED MODELS

Dry matter and tuber yields of potato grown in a sub-tropical environm ent were estimated employing simple radiation-based models which requi re meteorological information on air temperature and solar radiation. Two versions of the MacKerron and Waister (1985) model, in which estim ation of dry matter accumulation relies on a single composite paramete r, radiation use efficiency (RUE), were compared with the Versteeg and Van Keulen (1986) model, which explicitly accounts for temperature an d radiation effects on dry matter accumulation. In the original versio n of the MacKerron and Waister model, a linear change in the radiation interception factor with leaf area index is assumed; in the modified version an exponential change in the interception factor with leaf are a index is considered. The accumulation of dry matter estimated from a ll three models was close to the measured values throughout the growin g season, but estimates of tuber yield differed widely. Our analysis s howed that the best agreement with measured values was obtained using the MacKerron and Waister linear model with RUE values adjusted accord ing to the incident radiation level.