The Effect of Root Temperature and Nitrate/Ammonium Ratio on Strawberry Plants. II. Nitrogen Uptake, Mineral Ions, and Carboxylate Concentrations1

Strawberry plants (Fragaria ananasa Duch.) have shallow roots and are grown in the field during both hot and cold seasons. The possibility of irrigating and fertilizing the plants daily, through the trickle system, led to the question of what is the best nitrogen form and NO−3/NH+4ratios to be supplied to this crop during the growing season. The effect of four root temperatures (10, 17, 25 and 32 °C) and five NO−3/NH+4mole ratios (0⁄7, 2⁄5, 3.5⁄3.5, 5⁄2, 7⁄0) at constant total N in the solution was studied. To keep constant pH, total nutrient solution and root temperature, continuous flow techniques were used. The solution was flushed through 1‐L pots at the rate of 1 L h−1. When both N forms were present, the rate of total N uptake was higher than when NH+4or NO−3alone was present. The maximum uptake rate was found at 25 °C root temperature. Best conditions for growth were found at 25 °C root temperature when both N forms were present in equal concentration. A preference for NO−3uptake was found during flowering and the fruiting period. Ammonium was preferred during the vegetative growth period. Increasing root temperature decreased total cation concentration and especially that of K+, Na+, and Mg2+, and increased Ca2+in the roots of NO−3‐fed plants. The Na+was accumulated in the crown and did not move to the leaves and fruits. Increasing root temperature reduced inorganic anion concentration in the roots while increasing it in leaves of NH+4fed plants. In the fruits, the ratio of mole of charges of Ca2+to that of H2PO−4was about 1:1 for both N forms.