Phosphate uptake by lettuces and carrots from different soil depths in the field

Abstract

In order to investigate the depths in field soils from which plants derive their phosphate nutrition, uptake of s2P from depths of 6, 12, 24 and 36 inches was studied, using a shallow-rooted crop (lettuce) and a deeper-rooted crop (carrot). A soil at two different fertility levels was used, the higher level of fertility having been attained by heavy applications of farmyard manure over a period of twelve years.The exchangeable pool of phosphate in the high-fertility soil, at the depths investigated, was about twice that in the low-fertility soil. Total phosphate uptake by lettuces on the two soils was almost proportional to the size of the exchangeable pool, but the uptake by carrots on the high-fertility soil was much less than twice that on the low-fertility soil.Phosphate uptake, computed as the product of measured radioactive phosphate and the size of the exchangeable phosphate pool at the depths investigated, shows that lettuces derived almost all their requirements of phosphate from the uppermost foot of soil. Carrots obtained most of their phosphate from this layer, but also obtained appreciable amounts from depths of 24 and 36 inches.Some implications of these findings are discussed.

Effect of variety, soil fertility status and agronomic treatments on carrot mineral and phytochemical composition and consumer liking of flavor traits

“…Soil P is positively correlated with yield up to a point (∼200 μg g −1 soil P); above this level, additional soil P results in dropping yields . At later growth stages approaching maturity, tissue P does not continue to rise with increasing soil P . Potassium (K) does not have consistent impact on carrot yield or quality .…”