Effects of phosphorus and potassium supplied for the various stages of growth, on the yield and quality of seeds of chinese cabbage

Abstract

The experiment were carried out in sand culture 10 clarify the effects of phosphorus and potassium supplied for the various stages of growth, on the yield and quality of seeds of chinese cabbage. Phos-phorus concentration in the nutrient solution was 15ppm as P, and potassium concentration was 120 ppm as K. All other nutrient elements were given during all stages of growth in every treatment. The results obtained are as follows.
(1) Phosphorus experiment
The plants which were supplied with phosphorus from the planting time (Sept. 26) to the end of flo-wering stage (Apr. 26), had about the same seed yield as control plants supplied with phosphorus throughout all stages of growth. But the plants which were supplied with phosphorus until the ear-ly flowering stage (Mar. 28) or until the bolting stage (Feb.18), produced pretty lower yield due to smaller size of seeds compared with that of control plants. And the plants which were supplied with phosphorus during the period only from the plant-ing time to the flower bud differentiation stage (Dec. 17), had remarkably lower seed yield (only 2/5 of the control). The causes for this consisted in inferior development of the secondary and the tertiary lateral shoots, and furthermore in smaller size of seeds in the pods.
When phosphrus supply was withheld in the ear-ly stage, plant growth was retarded remarkably. And even in case of phosphorus application after Dec. 17 or after Feb. 18, growth recovery was slow, and seed yield was inferior to that of above-mentioned treatments. The plants which were withheld phosphorus supply during all growth stages, had scarcely any seed.
As for seed quality, the earlier the stage of growth which was stopped phosphorus supply, the lower was seed phosphorus concentration. And there was no differences of percentage germination among treatments, but incipient elongation rate of radicles was inferior in the treatments having smaller size of seeds.
From the results obtained, it is concluded that phosphorus supply from the planting time to the end of flowering stage, especially in the early stage, is necessary for good yield and quality of seeds.
(2) Potassium experiment
The plants which were supplied with potassium from the planting time (Sept. 26) to the full bloom ing stage (Mar. 22), had much the same seed yield as control plants supplied with potassium throughout all stages of growth. Even the plants which were supplied with potassium until the bolt-ing stage (Feb. 15) made no great difference in seed yield compared with the control. But in the treatment supplied with potassium during the period only from the planting time to the flower bud dif-ferentiation stage (Dec. 17), plants suffered from severe potassium deficiency and had remakably lower seed yield (about 1/3 of the control). The causes for this consisted in inferior development of the secondary and the tertiary lateral shoots. Seed size in this treatment was about the same as cont-rol, but some of seeds germinated within the pods.
Even if potassium supply was withheld in the early stage, plant growth became vigorus and seed yield also approached to that of the control, by the later application of potassium after Dec. 17. But potassium application after Feb. 15 was too late to recover the plant growth and seed yield. The plant which were withheld potassium supply throughout all stages of growth, had by far lower seed yield than other treatments.
As to seed potassium concentration, percentage germination and incipient elongation rate of radi-cles, there were no differences among treatments.
From the above results, potassium supply is ne-cessary at the least until the bolting stage for good yield and quality of the seeds.