Studies on the mineral nutrition of scotch pine in rendzina soils

Riispere, A.

Izv Akad Nauk Est Ssr Ser Biol Nauk 16(3): 247-274

1967


Accession: 025585134

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Abstract
The poor growth of scotch pine on rendzina soils is to an essential degree induced by the unfavorable physical and chemical properties of the humus horizon (A1). As the humus horizon lies immediately on dolomitized limestone, the soil has a high content of carbonates and the nutrition of plants is mainly determined by the system CaCC3-MgCO3-H2O-CO2. The predominance of this system produces a neutral or weak alkaline reaction and a high bicarbonate content in rendsina soils, which affect the nutrition and growth of pine disadvantageously. The unfavorable action of these factors is to a certain extent compensated by the high humus content in the soil. A high Ca carbonate content and neutral or weak alkaline reaction cause a low availability of P in rendzina soils, and the P is a main growth-limiting nutrient on these soils. The supply of pine seedlings with other nutrient elements (N, K, Ca, Mg, Fe) are sufficient. The intensive uptake of Ca does not induce the phenomena of antagonism in the absorption of other cations. The deficiency of P is not the single cause of inhibited growth of pine seedlings on rendzina soils, for there was no remarkable growth response in spite of an intensive uptake of P after the addition of this nutrient in a well-soluble form to natural soils. The direct inhibitory effect of high pH and bicarbonate ions in soil, which induce the inactivation of absorbed nutrients (especially of Fe) and reduce the activity of the metabolic processes in plant tissues should be considered. The nutritional conditions of scotch pine on rendzina soils are improved by the acidification of the soils with sulphuric acid or elementary S, after which the carbonate system in soil is replaced by the system CaSO4-MgSO4-H2O. This results in a more favorable soil reaction and decreases the deteriorating effect of bicarbonate ions. Acidification increases the solubility of P in soil and prevents the inactivation of absorbed nutrients in tissues, which results in increasing the total metabolic activity of plants. The addition of P to acidified soils considerably improves the growth of pine seedlings. Though in natural rendsina soils the varying of the total carbonate content and the ratio of Ca and Mg carbonates do not affect the growth and nutrition of pine seedlings to any considerable extent, it is necessary to consider those factors when acidifying the soil. Due to the formation of well-soluble MgSO4, the acidification of soils with a relatively high MgCO3 content may result in an excessive increase of the concentration of the soil solution. It may induce serious injury to roots and a destruction of the whole plant. The CaSO4 formed at an acidification of soils is not deleterious to plants (even if it occurs in large quantities) because of its low solubility.