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Abstract "Heft 27"

Freiburger Bodenkundliche Abhandlungen

Schriftenreihe des

Institut für Bodenkunde und Waldernährungslehre
der Albert-Ludwigs-Universität Freiburg i.Br.
Schriftleitung: F. Hädrich

Heft 27

H.-P. Ende

Wirkung von Mineraldünger in Buchen- und Fichtenbeständen
des Grundgebirgs-Schwarzwaldes

Freiburg im Breisgau 1991

ISSN 0344-2691


In Norway spruce stands (Picea abies (L.) Karst.) and in a naturally regenerating stand of European beech (Fagus sylvatica L.) in the bedrock region of the Black Forest, short-term and medium-term effects of rapidly soluble mineral fertilizers have been investigated. The nutritional state was evaluated periodically using needle, leaf, and soil analyses. The state of health was. estimated by symptom diagnosis and terminal shoot growth was measured within the beech stand. The investigations were carried out at already existing as well as newly established experimental sites.

Historical studies about the new sites prove that for more than 600 yr the forest had been utilized by clearcutting of large areas and other practises leading to extremely high exports of biomass. The consequences were high losses of nutrient elements, especially of M g and Ca, as well as soil erosion. Calculations of the available soil water suggest that there were several long dry periods between 1975 and 1989 damaging the beeches and leading to yellowing phenomena at these sites. Soil and plant analyses confirm that the pronounced symptoms in the beech and spruce stands are due to specific, extreme Mg deficiency. For one growing season, the seasonal variation of nutrient contents in leaves of the terminal shoot has been investigated within the beech stand. Compared to other authors' findings, the main nutrients took a similar course, but on a substantially lower level. A few weeks after fertilization with MgSO4, the aim of a rapid mitigation of the acute Mg deficiency was achieved. When comparing the three application rates it becomes evident that the lowest rate (500 kg*ha-1) was sufficient and had a more balancing effect on the nutrient element contents than had the double and treble rate. On the other hand, a dose of 2000 k g " h-1 a did not lead to nutritional problems. Compared to the control plot the SO4-S as well as the total S contents of beech leaves were increased pronouncedly after fertilization with MgSO4. However, only the rate of 500 kg*ha-1 enhanced the relation of organic S to SO4-s. in none of the plots the sum of P and S contents in the beech leaves did exceed 0.12 mmol'g-1 d.m. In the control plot, the P contents were higher than the organic S contents, whereas in the fertilized plots (500 or 1000 kg'ha-1) P contents equaled organic S contents. The data underline the importance of a fractionated S analysis for investigations into the effects of S inputs to forest sites. The chemical soil analyses indicate that the application of Mg sulfate initially reduced the availability of K in the upper soil. K supply of the plants, however, remained sufficient for three growing seasons. The range of supply with P . was not changed -after fertilization. pH values (CaCl_) were decreased 0.2 units at the most. On two fertilized plots the short-term effect of fertilization on the Mg supply could also be demonstrated from soil analyses.

One growing season after application of MgSO4, the vitality of the fertilized beeches was remarkably improved compared to the control plot, manifesting itself in a significantly higher shoot growth, slightly increased chlorophyll contents of the leaves and a drastic reduction of deficiency symptoms. The lowest rate (500 kg*ha-1) exhibited the best effects on vitality. In a spruce plantation, fertilization with ammonium sulfate did not induce Mg deficiency. In contrary, the contents of all analyzed elements in the needles except for Ca were enhanced, especially of K. After fertilization with Mg sulfate, extreme Mg deficiency was mitigated within the first growing season by the highest application rate and after two growing seasons by the lower rates. At the end of the first growing season, only Ca contents of the needles were decreased, whereas Mn, Zn and Al were increased. The S nutrition of the fertilized spruces was remarkably improved without changes in the organic S:N ratio of current needles CO.040 as in the control plot). In four-yr-old needles, the organic S:N ratio decreased with higher application rates indicating that excess sulfate was stored in the older needles.

At the experimental sites established in 1984, the applied fertilizers contained NO3-N, SO4-S, K, Ca, Mg, Mn and Zn in different combinations. In general, Mg fertilization improved Mg nutrition in coniferous stands insufficient or deficient in Mg. Mg sulfate had a more sustained effect than Mg nitrate. The Zn contents of the needles often increased together with the Mg contents. Fertilization with Ca nitrate enhanced the Ca and K contents only temporarily. On a K deficient site two trials with different K fertilizers failed. Total S contents measured at part of the sites in 1986 and 1988 seem to be insufficient. At some of the sites, P nutrition was deficient. Statistical relations between nutrient contents of the needles support presumptions that the Mg and Ca supply of some of the sites has been deteriorated by intensified nitrification processes.

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