Studies on the nitrogen nutrition in tomato plants. I

Abstract

1. A study on the effects of various nutrient levels, especially excess level of nitrogen, upon the seasonal nutrient absorption by tomato plants and the growth response was undertaken in water culture from June 17 to September 9, 1953. 2. Uniform Marglobe tomatoes, at the seven leaf stage, were transplanted to the 35l glazed earthenware pots. During the season, the nutrient solution was aerated by bubbling method continu-ously, and was renewed every week. At the same time, chemical analysis of the nutrient solution and the measurement of plant growth were performed. 3. The following levels of the nutrient solu-tion were used: nitrogen levels 50, 100, 200 and 400 p.p.m. Standard level (treatment N in series A) was N, P, K, Ca, Mg, and S: 100, 20, 80, 70, 25 and 33 p. p. m. respectively. In other treat-ments in series A, all the nutrient levels were varied in proportion to the nitrogen level. In series B, the nitrogen levels were changed such as 50, 100, 200 and 400 p.p.m. and the other elements were always provided in constant proportion. pH of the solution was adjusted to 5.6-5.8. 4. In the 50, 100 and 200p.p.m. nitrogen plots, nitrogen absorption process were nearly similar: increased gradually until the third clusters are going to bloom, afterwards the increase and de-crease of the absorption continued alternately without great change to the end of season. How-ever, in the 400 p.p.m. nitrogen plot, nitrogen absorption was quite different from that of the lower levels. Amount of absorbed nitrogen was very large in early growing season and this ab-sorption continued to early August, but thereafter decreased. Thus, nitrogen absorption of the 400 p.p.m. nitrogen plot seemed to have been always excessive luxury. 5. The absorption process of phosphorus was analogus to that of nitrogen. 6. The absorption process of potassium was also analogus to that of nitrogen. However, in high nitrogen and low potassium level (N 400 p.p.m., K 80 p.p.m. ), potassium absorption increased up to late July, and then decreased rapidly. 7. Amount of nitrogen and phosphorus absorption increased as these elements increased in the culture solution, there were no effects of the other elements upon their absorption. Potassium absortion depends upon the level of applied potassium in the 200 p.p.m. nitrogen plot, but the absorption was controlled in the 400 p.p.m. nitro-gen plot, especially reduced in the 400 p.p.m. N, 80 p.p.m. K plot (N:K=5:1). Thus, the potassium absorption was affected not only by the level of potassium in the nutrient solution, but also by the level of nitrogen and the ratio of N/K. 8. The absorption process of water was proportional to variation of atmospheric temperature. 9. Growth and fruiting behavior of plants in all the treatments were normal as the field condition. When the nitrogen level was excessive, excessive symptoms such as vigorous vegetative growth, delaying of anthesis and unfruitness were not occured. 10. There were not always constant tendency between inorganic constituents in the leaves and amount of nutrient absorption from the solution by plants.