Temperature and plant responses to paper and plastic protectors on cantaloupes

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Introduction

When warm-season plants are grown during the winter months, some means of microclimatic manipulation becomes essential. This is the case in the production of cantaloupes in the desert areas of the south, vestern United States. At EI Centro in Imperial Valley, for instance, the average maximum in January of 1959 was 73.3° and the average minimum was 39.8° F. The soil temperature varies from a maximum of about 75° to a minimum of about 45° F. According to (Knott (1957)),5 the optimum temperature for cantaloupe growth is a monthly average of 90° during the day and 60° during the night. The optimum soil germination temperature is about 90° F. It is obvious, then, that conditions existing in this area during January are far from ideal for the germination and growth of cantaloupe plants.

In contrast to the use of plant protectors in many other areas of the country, those used during the winter season in the desert areas of California remain in place for as long as three months. Cantaloupes planted during December remain under the protection of the shelters for nearly half of their life span. Any device employed under such conditions must meet certain requirements in order to be of value. Conditions should be such that rapid growth occurs and vigorous and hardy plants are produced. Environmental modifications which would create conditions for the plants more ideal than those naturally occurring would be: increased daytime air temperature, but not in excess; maximum increase in nighttime air temperature, hence protection from frost; increase in soil temperature; and maintenance of relative humidity at moderate levels. In addition to the conditions which relate directly to plant growth, shelters must also provide protection from wind and blowing sand.