Abstract
In 1995 and 1996, hourly soil temperature at 0.1 m below the soil surface was measured for eight mulch-irrigation-fertilization treatments under which pepper (Capsicum annuum L. cv. King Arthur) was grown. Hourly meteorological parameters (rainfall, relative humidity, air temperature, wind speed, and solar radiation) were also measured. Over both years, soil temperatures under non-mulched treatments were cooler than under mulched treatments. The temperatures of non-mulched treatments generally increased and decreased earlier and faster than their mulched counterparts. Non-mulched treatments showed slower initial plant growth as assessed by total leaf area, but their increases in leaf area later in the season surpassed those of the mulched treatments. Late-season leaf area and total yield although numerically smaller for non-mulched treatments, were not significantly smaller than for mulched treatments. According to stepwise and Maximum R2 Improvement (MAXR) regressions between meteorological parameters and soil temperature, mean air temperature and mean radiation in the preceding 6-48 h were the best predictors of soil temperature. Wind speed (1995) and relative humidity (1996) were factors of secondary importance, while rainfall had little or no effect. The MAXR-derived equations gave better predictions of soil temperature in a given year than did stepwise-derived equations. Predictions of 1995 soil temperature based on 1996 data-derived regressions showed good agreement [per cent root mean standard error (% RMSE) <8], whereas the converse (1995 predicting 1996) gave generally poor agreement (% RMSE as high as 177).
