Critical chlorophyll, total nitrogen, and nitrate‐nitrogen in leaves associated to maximum lettuce yield

Abstract

An experiment was conducted to establish chlorophyll, nitrate‐nitrogen (NO₃‐N), and total nitrogen (N) critical concentrations in lettuce (Lactuca sativa) leaves that are associated with maximum dry matter yield. Six N levels (0, 60, 120, 240, 480, and 960 mg.kg^‐1 soil) as ammonium nitrate (NH₄NO₃) were applied in a randomized block design with four replications. Two wrapper leaves were collected at the eighth‐leaf stage and analyzed for their chlorophyll a+b and total N contents. Forty‐five days after transplanting, plants were harvested, dried, and analyzed for their NO₃‐N and total N contents. Critical levels associated with maximum lettuce yield at the eighth‐leaf stage were: 1,837 mg chlorophyll kg^‐1 fresh weight and 4.27 g N 100 g^‐1 dry matter, and at harvest: 6,361 mg NO₃‐N kg^‐1 dry weight and 3.75 g N 100 g^‐1 dry matter. In the soil, N levels associated to maximum plant dry weight were 34 mg NO₃ ‐N kg‐¹ and 390 mg N kg^‐1.

Notes

CNPq Fellow.