The effect of soil nutrients on nodulation by Inga jinicuil, a leguminous tree used for shade in Mexican coffee plantations, is discussed. Nodulation and C(,2)H(,2) reduction of I. jinicuil seedlings, grown in soil, taken at different distances from coffee trunks, is described. Nodule biomass and activity are compared to the nutrient content of soils within various distances of coffee trunks. Seven coffee plantations, that employ I. jinicuil for shade, were examined with respect to nodule biomass, C(,2)H(,2) reducing activity, and soil characteristics. Highest nodule biomass was observed in soils with high levels of available phosphorus. High nitrogen content of the soil, on the other hand, appeared to be correlated with low nodule biomass. Potassium and magnesium, while apparently having little effect on nodule biomass, seem to be positively correlated with C(,2)H(,2) reduction.

Microbial biomass, microbial activity and enzymatic activity were determined in soil samples originating from a field experiment at the Askov Experimental Station, where sewage sludge has been applied to plots yearly since 1973. The results showed, on an average of all soil samplings, that plate counts of bacteria, biomass determined by fumigation according to Jenkinson, ATP content, oxygen uptake and dehydrogenase activity were highest in soil treated with sludge with a high content of toxic metals, lower in soil treated with sludge with a low content of toxic metals, and lowest in untreated soil (control). In contrast, plate counts of fungi were highest in soil treated with sludge with a low content of toxic metals. The untreated soil yielded intermediate values. The results from the different methods were in the same order of magnitude as previously found in other field manure experiments at the Askov Experimental Station. A toxic effect of the metal accumulation on the soil microbial activity was not observed. However, the possibility that increasing concentrations caused by repeated applications of sludge with a high metal content eventually may lead to harmful effects cannot be ruled out.

The purpose of this research is to study the effects of fire on vegetation and soil properties after the first growing season in Mt. Chiak, Korea [R.]. With the basis of important value of species in each stand, status of species was assessed for three categories; Increaser species, Decreaser species, and Neutral species. Biomass was 2.2 times higher on burned area than unburned. This indicates that biomass was remarkably increased after fire. To evaluate similarity, coefficients of similarity among communities were obtained, and correlation coefficients were also estimated. These indices showed that burned and unburned community were markedly different. B1-stand and B2-stand appeared most similar to each other among stands. Species diversity was greater in burned than unburned stands. Soil pH value and organic matter content in burned area were significantly higher than those in unburned area. However, soil water content was lower in burned area. Thero was no effect of burning on soil pH value and water conetnt at 15-20 cm depth of soil.

Biodegradation of the carbon or specific carbons of a large variety of ¹⁴C-labeled organic substrates were followed in a closed, constantly aerated system in Steinbeck loam (pH 5.0) and Greenfield sandy loam (pH 7.0) over various periods of incubation at 22°C. Incorporation into biomass and stabilization in humus were estimated after 12 weeks of incubation. The labeled carbons in biomass were estimated using a slight modification of Jenkinson's fumigation method. Readily available substrates such as glucose, acetate, pyruvate, uracil, uridine, amino acids, and some polysaccharides were rapidly metabolized by the soil population, and after 8 to 12 weeks, about 80% or more of the substrate carbons had evolved as CO₂. After 12 weeks, about 20 to 40% of the residual carbons of these substrates were present as hiomass, and 60 to 80% was present as new humus. Glucosamine, cysteine, cellulose, protein, and some microbial and plant polysaccharides were degraded to a somewhat smaller extend, 60 to 70%, indicating some stabilization of the intact molecules or partial degradation products by incorporation into humus or by complexing with soil colloids or metals. About 10 to 30% of the residual carbons were associated with the biomass after 12 weeks. Most microbial cells and plant residues such as straw were utilized to a still lesser extent, with about 50 to 60% loss of applied C in 12 weeks and an incorporation of about 5 to 13% of the residual ¹⁴C into biomass. A fungal humic acid-type melanin was still more resistant, and less of the residual C, 0.2 to 1.3%, was present in biomass at 12 weeks.

Studies on biological activity of soil complex were carried out in 1978 in two grassland ecosystems in Upper Silesia affected by coal industry pollution. In comparison to less contaminated environments in the ecosystems examined the following were observed: considerable restriction of green parts of plants as compared with the weight of their root system, poorer both species composition and biomass of soil fauna as well as lowering the CO2 diffusion from the soil. (Pilarska, J.; Cianciara, S.; Urban, E.; Prus, M.)

The distribution of fertilizer nitrogen in soil and needle biomass of an 120-year-old stand of Scots pine was studied over a period of six years. The nitrogen was applied as ammonium nitrate or urea and at rates of 150,300 and 600 kg N per hectare. The soil investigations showed that, at the lowest nitrogen application rate, 21 % of the ammonium nitrate and 49% of the urea nitrogen were immobilized in the soil in nonexchangeable form. For the corresponding treatments the losses by leaching were estimated to 3040% and 0-lo%, respectively. The accumulation of fertilizer nitrogen in the needle biomass culminated during the third growing season. Relative to control, the total nitrogen accumulation for the lowest ammonium nitrate and urea application rates then amounted to 174 and 134% respectively. As regards volume growth, the ammonium nitrate was greatly superior to urea at the two lowest nitrogen application rates. The dose of 600 kg N per hectare proved to be over-optimal as far as the ammonium nitrate source of nitrogen was concerned.