Nitrate Accumulation in Spinach Grown Under Different Light Intensities1,2

Abstract ‘Winter Bloomsdale’ spinach plants were grown in a growth chamber with a light intensity of 2400 ft-c until 2 weeks before harvest when light intensity treatments of 600, 1600, 2400, and 3500 ft-c were imposed. The total N and NO 3 concn of the leaves were increased by the addition of N to the soil and by reduction of light intensity. At 600 ft-c the plants accumulated NO 3 -N and total N at all soil N levels, but response to soil increments of N was greater at higher light intensities. The concn of K in the tissue increased with a reduction in the light intensity from 2400 to 600 ft-c or application of N fertilizer to 200 mg/kg of soil. Less P was found in spinach leaves as N fertilizer was added to 100 mg/kg of soil. The P content was variable with light intensity.