Slow migration of capsicum oleoresin in a sandy loam soil

A mixture of 16.47±0.038 L concentrated capsicum oleoresin with 163.8±3.63 L water and a total of 17.2 L concentrated soybean oil with 177.1 L water was dispensed over five 4.87 m×4.87 m plots via a grid of 128 augured holes (≈15 cm-diameter×≈30 cm deep) in a compacted, sandy loam soil. During the next 9 days, a total of 37 soil samples were obtained from these plots and other off-plot areas. Spectrophotometric analyses of dual aliquots of soil samples were performed to detect absorbance of capsaicin (λmax at 282 nm). Analysis of variance showed that absorbance readings from points of capsicum application (augured holes) were 30-fold greater than for samples obtained 30-40 cm distant (F=19.21, df 1/4.22, p<0.0105). Soybean-oil plot and off-plot soil samples yielded negligible absorbance readings. Thus, capsicum oleoresin persisted for ⩾10 days in this type of soil, but migration was minimal.