Studies on the Dry Matter Production of Sweet Potato : III. The relation between the dry matter production and the absorption of mineral nutrients

Abstract

These experiments were carried out in order to make clear the relation between dry matter production and absorption of the three major elements under various cultural conditions, and to find out the factors which influenced the absorption of nutrients in sweet potato plants. 1). In the course of absorption of the three major elements, it was recognized that the process was greatly influenced by soil temperature during early growing stage. Sweet potato plants could hardly absorb the nutrients and slightly produce the dry matter at about 20°C of the culture solution. But both dry matter production and absorption of nutrients markedly increased with rising up of the solution temperature. 2). The total dry matter production per unit field area was most remarkably governed by the amount of absorption of potassium among others. There was a close relation between the amount of nutrient absorbed and the increasing weight of leaves in early growing stage, and at the harvesting time there was a high correlation between the leaf area duration and the amount of nitrogen absorbed. 3). The amount of nitrogen absorbed was increased by late planting compared with early planting. As a result, it caused an increase in leaf area duration in late planting plots. Increment of leaf area duration had also other effect, e.g. total dry matter production was increased in the infertile field, while, in the fertile field, it was decreased by the decline of Net Assimilation Rate owing to excessive increase of the leaf area duration (Table 2).