Effect of Potassium and Moisture on Rape Growth and Its Nutrient Uptake

The Interaction between potassium and moisture during the growth of and nutrient uptake by rapeseed plants grown on K-deficient soils has been investigated in this Study. The results show that the dry weight of the above-ground parts of the plant appears to be somewhat reduced when the volume water content of the soil remains 0.15 for 3 successive days. As the shortage in the soil water continues, the height of the plant root and the permeability of the root plasmalemma are markedly affected; the stem thickness and leaf area are reduced. However, K application can increase the dry matter weight of the above-ground parts, the thickness of the stem, and the area of the leaf. Application of K can also maintain a comparatively low water potential(ψ) and a comparatively high moisture content in the leaves, thus increasing the drought-resisting ability of the plant. When the volume water content of the soil is raised to 0.30, leaf yellowing as a symptom of nutrient deficiency appears on rapeseed plants grown on K-deficient soils. With increase in soil moisture content, the Ca concentration of the aerial parts of the rapeseed plant without K application increases while the K concentration decreases. Both K application and the soil moisture regime have very little effect on the Mg concentration in the plant. Under soil moisture stress, the nitrogen content and total amount of alnino acids in rape leaves increases; and thus more proline and glutamic acid is formed. On the other hand, the impact of soil moisture on plant's dry matter is governed by the status of potassium nutrition. On soils with low K, the moisture content has very little effect on yield; when K fertilizer is applied, however, the moisture content shows a very significant effect on yield increase.