EFFECT OF LIMING MATERIALS ON SOIL AVAILABLE NUTRIENTS, YIELD, AND GRADE DISTRIBUTION OF DOUBLE-CROPPED TOMATO AND CUCUMBER GROWN WITH PLASTICULTURE

Abstract

For economical reasons, cucumber (Cucumis sativus L.) may be grown as a double crop after tomato (Lycopersicon esculentum Mill.). In this production system, plant nutrition may be limited for the second crop due to pH change or insufficient levels of calcium or magnesium. The objective of this 2-year field study was to compare the effects of selected liming materials on yield and grade distribution, and soil available nutrients of a tomato/cucumber double crop produced with plasticulture. Liming materials were compared to a control and a CaSO₄ treatment based on the same neutralizing value as standard agricultural limestone. Supplemental N fertilization was provided by weekly injections at a rate of 7 kg/ha/week from ammonium nitrate (NH₄NO₃) or calcium nitrate [Ca(NO₃)₂]. Each year, soil samples were collected at the beginning of the study and after each crop to determine nutrient availability. All liming materials raised soil pH in 1998 and 1999 over the unlimed control, though not to the target level for tomato and cucumber production (pH 6.5). Throughout the study, agricultural limestone, a high CaO-containing blend (calcitic blend) and a CaO/MgO (dolomitic blend), resulted in greater fruit weights compared to the control and CaSO₄. These materials, along with quick lime (CaO), provided higher levels of soil Ca and Mg available for plant growth. However, it was found that current recommendations for potassium (K), regardless of liming source, were not adequate for optimal soil reserves and yields in this tomato/cucumber cropping system. Ammonium nitrate as a source of N for fertilization was as effective as Ca(NO₃)₂.

ACKNOWLEDGMENTS

The authors wish to thank Jim Pitts, Superintendent, Chilton Area Horticulture Substation, for his assistance in day-to-day operations and data collection throughout this study.