Studies on the sodium chloride injury of vegetable crops in relation to the form of nitrogen in sand culture. II

Abstract

Spinach, Chinese cabbage, celery, turnip, and carrot were grown in sand culture under glass and were supplied with NO3 (a mixture of nitrates of K, Ca, and Mg), NH4+NO3 (ammonium nitrate), or NH4 (ammonium sulfate) in the absence and presence of NaCl, to study the sodium chloride injury of these crops in relation to the form of nitrogen supplied. The nitrogen concentration of any nutrient solution was equally 10m.e./l (140ppm), and the concentration of NaCl added to the solution was 8000ppm for spinach and Chinese cabbage, 6000ppm for celery, 2500ppm for turnip, and 4000 ppm for carrot. The pH of the solutions was adjusted to 6.2-6.4 in all cases.1. Both in the absence and presence of NaCl, plant growth was much better with NO3 than with NH4. And NH4+NO3 plants showed growth similar to or less than that shown by NO3 plants. Effect of NaCl on the yield of crops was not always constant with each nitrogen form.2. The dry weight percentage of plants generally incresed with the increasing supply of NH4-N.3. In the absence of NaCl, plants supplied with NO3 developed no specific symptoms; but NH4+NO3 plants produced darker green foliage than NO3 plants in some crops, and produced uneven or leathery leaves in Chinese cabbage. The supply of NH4 alone generally caused various specific symptoms, such as entire or interveinal chlorosis, burn, or withering of leaves. The rate of dead leaves increased as the amount of NH4-N increased. Some crops supplied with NH4 alone had brownish or purplish rootlets.In the presence of NaCl, the supply of NH4-N crops caused serious symptoms of malnutrition more markedly than in the absence of NaCl with NH4 alone chlorosis was developed markedly in general, and leaves of some crops were fragile. In Chinese cabbage, NH4+NO3 caused marginal rot of younger leaves, symptom of Ca deficiency, more markedly than NO3; and plants supplied with NH4 alone were severely stunted in growth showing entire chlorosis, marginal rot, and burn of leaves. In carrot, branched roots occurred to a high degree with NH4+NO3 or NH4.4. In the absence of NaCl, as the proportion fo NH4-N in the solution increased, N content of both leaves and roots tended to increase; and P content of leaves similarly increased, while that of roots showed an irregular tendency. Content of K, Ca, or Mg of both leaves and roots generally decreased with the increasing supply of NH4-N.In the presence of NaCl, similar tendencies as mentioned above were obtained for each element, except for N in leaves which mostly decreased with the supply of NH4-N, and the content of any essential cation was generally depressed by the interaction with Na. Moreover, Cl or Na content of leaves increased with the increasing supply of NH4-N, while that of roots showed a variable tendency with crop species.5. It is concluded that NO3-N is much more favourable than NH4-N as the nitrogen source for the crops tested, especially in the presence of excess NaCl. Application of NH4-N in the presence of excess NaCl may cause marked interference in absorption of essential cations, especially of Ca, and increased accumlation of Cl or Na in leaves.