The Effect of Root Temperature and NO⁻₃/NH⁺₄ Ratio on Strawberry Plants. I. Growth, Flowering, and Root Development¹

Abstract

Abstract The purpose of this work was to study the effect of various NO − 3 /NH + 4 ratios in the nutrient solution at various root temperatures on strawberry ( Fragaria ananassa ) plants. The results could lead to a suitable NO − 3 /NH + 4 ratio of the fertilizer solution to be applied in field‐grown strawberry plants in different seasons on sandy soils. 3 Strawberry plants were selected for uniformity and transferred individually to a 1 L container through which the nutrient solution was flushed at a rate of 1 L/h. The total N concentration was 7 me/L. Five ratios of NO − 3 /NH + 4 , 7/0, 5/2, 3.5/3.5, 2/5, and 0/7, respectively, were used, each at four root temperatures (10, 17, 25, and 32°C). Constant NO − 3 /NH + 4 ratio, constant total nutrient concentration, and constant pH (6.2) were maintained for 8 weeks. There is a general decline in root growth with increasing root temperature when a single source of N is supplied. This decrease is followed with a decrease in the sugar concentration of the roots. At 32°C root temperature gradual increase in the NH + 4 fraction in the nutrient solution is followed by gradual deterioration of the plants to a complete death at 100% NH + 4 . This death is related to the depletion of sugars and possible shortage of oxygen in the root cells due to NH + 4 metabolism in the root.