2018 ASHS Annual Conference

In the southeastern U.S. many vegetable growers produce multiple crops over several years on plastic mulch in order to reduce input costs for the crops grown. Typically a high value crop such as bell pepper (Capsicum annuum) or tomato (Solanum lycopersicum) will be grown first, followed by lower valued crops such as squash (Cucurbita pepo) and even cabbage (Brassica oleracea var. capitata). One problem encountered is that there is no practical way to increase the soil pH in the planted bed for second or third crops. Generally limestone-based products are insoluble and not appropriate for injection through drip irrigation. Recently, a finely ground (<0.5 micron) liquid limestone based product (Top Flow 130; Omya, Oftringen, Switzerland) was developed for agriculture use to be injected through drip irrigation tubing. To test the efficacy of Top Flow 130, 0, 94, and 187 L·ha^-1 of product were injected through drip irrigation and soil pH and nutrient content evaluated 7, 17, and 28 d after injection. Soils tests were conducted using the Mehlich 3 extraction method. The study was arranged in a completely randomized design with four replications. Each plot was a plastic mulched bed approximately 24 m-long. Flow rates measured before and after injection were not affected by treatment, suggesting that the liquid lime product did not clog emitters. There were significant interactions between application rate, sampling time, and distance from the emitter for change in soil pH and calcium level. In general, both application rates led to a significant increase in soil pH and calcium concentration at the emitter location and a distance of 10 cm from the emitter. Soil pH and calcium concentrations did not significantly change when measured at 20 cm from emitters. The increase in pH and calcium concentrations at a distance of 10 cm from the emitter were greater in those plots receiving 187 kg·ha^-1 compared to those getting 94 kg·ha^-1 of Top Flow 130. The effects on soil pH and calcium concentrations occurred within 7 d after injection the product, with no significant differences occurring between the 7, 17, and 28 day sampling periods at each sampling location (0, 10 and 20 cm from the emitter). These results suggest that Top Flow 130 could be used to adjust pH in a plasticulture system, but that the effects would occur within a zone of 10 cm on each side of the drip irrigation tubing.