EFFECT OF NITROGEN AVAILABILITY ON GROWTH AND NITROGEN UPTAKE IN LETTUCE

Fresh and dry matter production and nitrogen uptake during crop growth of two lettuce (Lactuca sativa L.) cultivars, cv.
Audran (butterhead lettuce) and cv.
Canasta (loose leaf lettuce), were studied in a field trial at different levels of fertilizer-N (0, 50, 100 and 200 kg N ha^-1) broadcast at transplanting.

On a dry matter basis, the relative growth rate (RGR) was not strictly related to reduced-N concentration (total-N minus nitrate-N) while, on a fresh weight basis, there was a linear relationship which was cultivar-specific and independent of fertilizer-N rates.
This was mainly due to the effect of N availability on nitrate accumulation because of its osmotic effect on plant water content.

Apparent fertilizer-N recovery declined linearly with the increase in fertilizer-N rates in both cultivars.
The estimated fertilizer-N rate to obtain maximum fresh and dry weights was about 155 kg N ha^-1 in both cultivars.
At that rate, the estimated N uptake was about 145 kg ha^-1 in cv.
Canasta and 131 kg ha^-1 in cv.
Audran.
Considering that the N uptake with 0 kg ha^-1 of fertilizer-N rate was 63 kg ha^-1 in Audran and 58 kg ha^-1 in Canasta, about 80 kg ha^-1 of mineral nitrogen remained in the soil at harvest.

VIII International Symposium on Timing Field Production in Vegetable Crops

F. Tei, P. Benincasa, M. Guiducci

Lactuca sativa L., cultivars, nitrogen concentration, relative growth rate, nitrogen uptake, nitrogen balance

https://doi.org/10.17660/ActaHortic.2000.533.47