Microbial biomass, microbial activity and enzymatic activity were examined in soil samples originating from a field experiment, which was initiated in 1893 at the Askov Experimental Station. The unmanured, manured and fertilized plots, respectively, were since that time treated in the same way. The results of the microbiological investigations varied with the time of the soil samplings. On an average of all soil samplings, plate counts of fungi, ATP content, oxygen uptake and dehydrogenase activity yielded the highest results for the fertilized soil, lower results for the manured soil and the lowest results for the unmanured soil (control). Plate counts of bacteria and the biomass determined by fumigation according to Jenkinson yielded the highest results for the manured soil. In general, the differences between the microbiological results for unmanured, manured and fertilized soils were small.

A greenhouse study was conducted to evaluate growth and mineral nutrition responses of Typha latifolia L. (common cattail), a ubiquitous emergent aquatic macrophyte, to changes in certain environmental conditions. Typha was found to be sensitive to temperature and nutrient changes in the soil. Elevations in temperature affected the growth and mineral nutrition more than increases of the soil N and P. An incremental change of 7°C, from lg to 25°C, increased the shoot biomass 1.7 times. However, a 14°C elevation, from lg to 32°C, increased the biomass only 2.2 times. Of the elements analyzed (Al, Ba, B, Ca, Cu, ¹³⁷Cs, Fe, K, Mg, Mn, N, P, Sr, and Zn), only the Cu content was not changed by elevated temperatures. In general, elemental contents increased with increasing level of temperature, paralleling the biomass production. The results indicate that Typha's potential to remove some elements from contaminated soil may be influenced by certain environmental factors.

1. Compound fertilization inhibits the enzymatic activities of the hydrolytic decomposition of litter. 2. In the nursery soil examined urease and xylanase activities had been distinctly reduced after six weeks, whereas cellulase and invertase activities had scarcely been affected after this period. 3. Through compound fertilization the enzymatic activities of intracellular dehydrogenases increased by the same amount as the microbial biomass. 4. It was proved that, in the case of litter decomposition, extracellular biochemical activity was not at all bound to be in direct relation to the microbial biomass, but that it is closely connected to the decomposible organic matter. 5. An additional treatment of the soil with cupric sulfate brought a toxic effect. Dehydrogenase activity was inhibited by a further 72 per cent, urease and xylanase activities by 30 per cent. Invertase activity was only reduced by 15 per cent and cellulase activity by 10 per cent. 6. The present studies make it possible to understand the complicated interaction between soil microorganisms and the plant, point to the inhibition of litter decomposition by chemical soil treatments (fertilization, addition of a heavy metal) and suggest the competition for nutrients between the plant and the soil microflora. 7. A new method for the determination of invertase activity in soils was developed.

Grain production in two 1/4 hectare plots gave 2971 and 1380 kg/ha for an average yield of 2175 kg/ha. Average yield for local farmers was 1700 kg/ha. Weed biomass accounted for 50 per cent of total biomass in the hydric Site 4, but held 64-83 per cent of the total nutrients. In the mesic Site 1, values were 5 per cent and 3-29 per cent respectively. Canna edulis was the most abundant weed species. Soil nutrient levels neither increased or decrease significantly between clearing and harvesting. Any decline in future crop production would be due to increased weed competition and not a decline in soil fertility. Weevil (Sitophilus zaemis) infestation is a serious problem in hybrid corn not encountered with local varieties

A marginal agricultural area (soil pH = 4.0, sandy moraine) in Mols Bjerge, Jutland, Denmark, was grazed by a herd of nursing cows for five years. The amount of exchangeable Ca, Mg, K, Mn, Fe and P together with the pH, bulk density and organic material in the upper 10 centimetres of the soil as well as the amounts of the above elements in the above ground biomass were measured over the period. Grazing did not cause any significant decline in the amounts of available nutrients in the soil even though no fertilizer was added, but the exchangeable amounts of Ca, Mg and to some extent Mn and P were increased as a result of grazing. No changes were detected in the pH of the soil, but the bulk density and the content of organic material in the upper soil layer were increased. Apart from P, the deposition of nutrients from precipitation was greater than the amounts removed from the area with the carcasses