The effectiveness of plastic and petroleum mulches did not change in tests at two different locations on two different soil types in San Joaquin Valley cotton fields. Higher soil temperatures generated by all of the mulch test treatments resulted in earlier cotton germination and faster development, but ultimate plant sizes were the same. The mulches did not affect cotton quality, but shifted a greater percentage of the yield into the first picking. Although yield increases alone may not return the cost of treatment, reductions in hand labor made possible through precision planting as part of the mulching operation offer some compensation.

Film and equipment were provided by Spencer Chemical Company, Kansas City, Missouri. Humble Oil and Refining Company, Houston, Texas, provided the petroleum mulch.