Excess rainfall during planting and early growth did not occur this year, as in 1998 (other than February). We received 4.37 inches of precipitation in February, on fourteen days. Rainfall after February was average or lower than average. Low air temperatures were a problem in March and April. The average daily air temperature in March was 51^"F, while April was 59^"F. The real culprit, however, was the minimum air temperatures. These averages were 38^"F in March and 44^"F in April. Temperatures in this range are not favorable for rapid tomato growth and the crop did not "move" like normal. The minimum air temperature on April 9 was 28^"F for several hours, which damaged or killed many plants that were larger than the cotyledon growth stage. This caused some replanting, if that was an option. There were 16 days with minimum air temperatures lower than 40^"F during the growth period. There were only six days that exceeded 100^"F during that period.

Environmental conditions during this test were more favorable for good plant growth and fruit development. There were only 11 days when the maximum air temperature exceeded 100^"F. The temperatures could only be described as moderate, compared to other years. The night temperatures were several degrees cooler, which was favorable for good pollination, fruit set and field-holding abilities. It was just about perfect conditions, as reflected in the high yields obtained locally. There was no substantial precipitation received during the mid-season test growing period.

Environmental data for both tests are contained in the following table. All data are from a California Irrigation Management Information System (CIMIS) automated weather station maintained by the Department of Water Resources. The Colusa station was used to obtain weather data for both test sites.

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Copyright © 1999 Colusa County Cooperative Extension, Univ. of California
Last modified: August 16, 2000