As. Claassens, INFLUENCE OF VARYING PHOSPHORUS SUPPLY ON THE GROWTH AND PHOSPHORUS COMPOSITION OF LETTUCE, Communications in soil science and plant analysis, 25(9-10), 1994, pp. 1209-1221
The effect of varying phosphorus (P) supply on the growth, yield, leaf
abnormalities, and nutrient composition was investigated for three le
ttuce cultivars (Chaparal, Wintercrisp, and Robinvale) in sand culture
and soil. The leaf P content for optimum yields varied between 0.40 a
nd 0.90% while higher than 0.90% P seemed to cause leaf abnormalities
in Chaparal and Winter-crisp. With high P supply, more calcium (Ca) wa
s necessary to overcome the detrimental effect of P. In soil, maximum
yields were obtained with a P supply level of 540 mg/kg P, while highe
r levels caused yield reductions. Soil analysis at the end of the expe
riment showed that a soil P content of 250 mg/kg P (Bray II) was assoc
iated with the best yield. When additional Ca was supplied to the soil
, yield reduction due to high P supply was reduced. The leaf abnormali
ties which coincided with the high P supply were similar to those whic
h have previously been described for auxin-type herbicide damage on le
ttuce.