Sequential cropping of vegetables on black plastic using two sources and rates of nitrogen fertilizers

Broccoli (Brassica oleracea), bell peppers (Capsicum annum var. annum grossom group), yellow summer squash (Cucurbita pepo var. melopepo), and tomatoes (Lycopersicon esculentum) were grown on an Etowah fine loamy soil during the seasons of 1982-1983 as single or double crops on black polyethylene film mulch at the Plant and Soil Science Field Laboratory, Knoxville, TN in order to compare the relative projected gross returns of each crop and crop sequence and to compare two different sources (urea and sulphur-coated urea) and rates (145 and 290 kg/ha) of nitrogenous fertilizers. The fertilizer was banded and incorporated beneath black plastic rows at the beginning of each growing season. Yields by grade were taken of each crop and wholesale prices were recorded at the end of each harvest. The recorded prices provided a common denominator of monetary value in order to compare estimated returns from the crops and cropping sequence.

During both years tomatoes were significantly higher in projected gross returns than all other crops and cropping sequences. The double crops of broccoli-pepper and broccoli-squash were not significantly different from each other in gross returns. The double crop of broccoli-pepper did not give significantly different gross returns than the single crop of broccoli in 1982 or 1983. The double crop of broccoli-squash was not significantly different in value than the single crop of broccoli in 1982 but did give higher gross returns in 1983. All other single crops with the exception of tomatoes were not significantly different in returns in 1982, yet were different in 1983.

There were no significant differences in projected gross returns between fertilizer treatments on single crops and cropping sequences either year except on the broccoli crop during 1982. The high rate of urea allowed broccoli to have significantly higher returns than from the other fertilizer treatments.

During both years of the study, yields of most single crops were not influenced by various nitrogen fertilizer treatments, except broccoli which was significantly increased as a result of the high rate of urea. Marketable yields of squash following broccoli and U.S. Fancy grade peppers following broccoli also increased as a result of a higher application rate of sulphur-coated urea.

The first crop planted in a double crop sequence demonstrated greater yields and projected gross returns than the second crop both years.