Tuberous Roots Of Sweet Potato Research Articles

Effects of the application time of nitrogen on the rate of nitrogen absorption as related to top growth, and formation and thickening of tuberous roots in sweet potato

Experiments on the application time of nitrogen fertilizer were carried out to clarify the mechanism of the formation and thickening of tuberous roots in sweet potato. Four types of soil classes, that is, sand, sandy loam, loam and clayey loam were used.In sandy soils, the application of nitrogen at about 30 days after planting was unfavorable to tuberous root formation during the one month period, mid-July to mid-August, because the higher rate of nitrogen absorption produced the vines growing vi gorously. However, the marked nitrogen absorption during the period of thickening growth after tube rous root initiation was favorable to the increase of yield of tuberous roots.In clayey soil, the application of nitrogen until 10 days after planting was favorable to both formation and thickening of tuberous roots due to the vigorous growth of vines having the high rates of nitrogen absorption throughout the growing season. Such a nitrogen status caused a higher yield of tuberous roots.

Studies on the Effects of Soil Physical Conditions on the Growth and Yield of Crop Plants : IV. Effects of the different soil Structures on a few plysiological characters of sweet potato plants.

These experiments were made on the relationship between the effects of soil structure on the growth and yield of sweet potato Plant, and a few physiological characteristics. The results obtained may be sammarized as follows. (1) By aggregating the soil, the growth of sweet potato plant was promoted and its total dry weight increased. As for the relationship between soil treatment and growth of different stage, it was found that the aggregate formation of the soil affected its growth in its late growth stage to a large extent and promoted especially the thickening of tuberous root. When the soil was made compact, the growth of the top parts of the plant became flourishing, but the thickening of its tuberous root was hampered considerably. (2) The authors examined the internal tissure of sweet potato's root in the aggregated soil treatment. As a result, it was found that the activity of cambium was vigorous and that the number of primary xylem was few. It was also observed that its root presented the condition liable to become tuberous root, and that the differentiation of root had advanced. (3) The nitrogen content of sweet potato was larger in the aggregated soil treatment than in the standard soil treatment, and the rate of soluble nitrogen content against total nitrogen content was liable to be higher in the standard soil treatment. (4) The phosphorylase and amylase activity in tuberous root of sweet potato was lower in its early growth stage, highest in its middle growth stage, and decreased slightly in its late growth stage. The value of isoelectric point of cell protoplasm of parenchyma in tuberous root was low in its early growth stage and became higher as its growth advanced. (5) With regard to the relationship between the soil managing methods and a few emyzme activities, phosphorylase activity was higher in the standard soil treatment in its early growth stage, but decreased in and after its middle growth stage, whereas amylase activity was higher in the aggregated soil treatment in its early growth stage but decreased in and after its middle growth stage. All this goes to show that the aggregated soil treatment offered more favourable internal conditions for the accumulation of starch in tuberous root than the standard soil treatment.

Effects of High Soil Temperatures on the Growth of Sweetpotato Plant.

1) Effects of high soil temperatures on the growth of sweet potato plant was investigated using soil thermostats at 32°C, 27°C and 23°C. The higher the soil temperature, the greater was the growth of vines. But, at 32°C, the growth of tuberous roots became poor, and some varieties tested did not produce any roots at all, and there was no difference between the results by 27°C and those by 23°C. So, the authors concluded that the optimum soil temperature for the growth of sweet potato plant ranges from 20°C to 30°C, and temperatures above 30°C are inappropriate for it. 2) The soil temperature was kept at 25°C in the daytime (a.m. 8.00 p.m. 6.00) and at 31°C in the night, and reversely at 31°C in the daytime, and at 25°C in the night. As a resuet of this test, high soil temperature in the night was proved to be a crucial factor for the growth. 3) The relation of the growing period to the high soil temperature (31°C) was examined, and it was found that the effects of the high soil temperature for 20 days after transplanting were not so remarkable for the growth of the tuberous roots of sweet potato, but the sametemperature after this period was crucially important. 4) It is known that the soil temperature at the late-planted fields is usually high above 30°C for about one month after the rainy season, and moreover, the high soil temperature prevails during the night for this period, and it is also confirmed that straw mulching is efficacious on late-planted sweet potato fields. Therefore, from the above points of view, it may be reasoned that the main cause of reduceds yields of sweet potatoes planted late is due to the high soil temperature.

Effects of Soil Moisture Content upon the Quality of Tuberous Roots of Sweet Potato

Effects of Soil Moisture Content upon the Quality of Tuberous Roots of Sweet Potato