ALBERT

Notes: Summary Fertilizing experiments have been established in the years 1955/56 in pine stands(Pinus silvestris) of very bad site quality in the forest districts of Amberg and Schwabach (Bavaria). The sites have a pure nutrient supply and have been gathered of forest litter in former time. In the plots unhydrous ammonia is compared with solid nitrogen fertilizers. In part the nitrogen fertilization is combined with application of lime, phosphate and KMg-fertilizer. The effects on the humus, the mineral nutrition of the trees, and their growth are investigated. Solid nitrogen fertilizers had only a weak effect in the soil. Unhydrous ammonia, which was injected in the humus layers and the mineral soil respectively, caused point by point chemical changes of humus and microbial conversions. 2 years after the application no higher mineral nitrogen supply was stated any more by incubation tests. The needle analysis, which were made every autumn showed, that after application of solid N-fertilizer the N-concentration in the half-year old needles had risen strongly (until the value, which is observed in well growing stands) already in the year of fertilization. Unhydrous ammonia caused only a moderate rising of the N-concentration. In the following years until 1961 the concentrations felt down again to the level of the non-treated plots. The weights of the needles increased very much in the first years, especially in the plots with solid N-fertilization. The concentrations of the other important elements remained on the same level. The current tree-growth rised in the 3 years after the year of fertilization in the plots with 200 kg/ha N in solid form at 95 %, in the plots with unhydrous ammonia at 46 %. This means in the case of solid N-fertilization already a lucrative rent.

Notes: Summary Equal fertilizing trials were established in 1956 in two spruce-stands (Picea abies) of bad stand quality class („Höhenbonität“ = III,0). One is situated near Munich on Rissmoraine, the other near Mähring (north-eastern part of Bavaria) in the low crystalline rock mountains. The main purpose was to compare solid nitrogen fertilizer with anhydrous ammonia concerning the effect on the mineral nutrition and the growth of the trees. In some plots the nitrogen fertilization was combined with application of lime and phosphate. 1956–60 yearly needle samples were taken. In autumn 1960 increment cores were taken. Needle analysis showed considerable differences in the main nutrient contents in the needles corresponding to their position in the upper tree crown. After fertilization the nitrogen contents raised remarkably for 3–5 years. In both trials the nitrogen salt fertilization effected a higher content of nitrogen in the needles than anhydrous ammonia. The wood volume increment, too, raised in the manured plots. With a retarting of 1–2 years the increase of the current wood increment responded to the higher level of the nitrogen contents in the needles. Only immediately after the application of anhydrous ammonia the wood increment was lower than that of the untreated plots. This probably was caused by mechanical injury of shallow roots with the ammonia injector and the initially very high ammonia concentrations in the injection points. The largest wood increment increase was effected in the plots where 200 kg/ha N as nitrogen salt were given. Significant and causal correlations are shown between the increase of the nitrogen content in the needles and the increase of the wood increment. Therefore it is possible to predict the increase of the current wood increment by means of needle analysis results. Five years after manuring a lucrative rent results from the fertilizer application in the plots near Munich. In the best responding plots with a wood increment increase of 15–18 cubic meters „Derbholz“ the net yield amounts from DM 800,— to 1300,— per Hektar in 5 years. Because of the unfavourable climatic conditions in the Mähring-area the effect of manuring was lower than in the Munich-area. Therefore in the Mähring-area no net yield results until now.