Ewald Wollny—A Pioneer in Soil and Water Conservation Research

Considerable emphasis has recently been placed on research in soil and water conservation. The soil erosion plots at the Missouri Agricultural Experiment Station, which were originated by M. F. Miller and his associates in 1917, are the classic examples of the amount of erosion taking place under various cropping systems (5). These plots have been the germ from which the soil and water conservation activities in this country have developed. Miller and his personal friend, H. H. Bennett, have indeed been the pioneers who have blazed the trails of thinking in the field of soil conservation in America. The former not only brought to light the fact that cultivation of sloping land resulted in large losses of surface soil but also opened a practical way of curtailing these losses through cropping methods. The latter has enlarged and carried this story to the American public with a sincere conviction that the fundamental assets of a great agricultural nation were rapidly diminishing and will continue to do so if adequate control measures are not initiated. It is interesting and important to note that from thirty-five to forty years previous to the highly significant developments in this country, some fundamental investigations relating to soil and water conservation had been carried out in Germany. The pioneer in this case was Ewald Wollny. His primary interests were in the field of soil physics with special emphasis on the fact that plant growth is dependent upon the physical properties of the soil. From 1878 to 1898 he published twenty volumes of the periodical "Forschungen auf dem Gebiete Agrikultur-physik" (investigations in the field of agricultural physics). Each volume was divided into three sections, soil physics, plant physics, and agricultural meteorology. Inasmuch as the raindrop is one of the important agencies involved in changing the physical properties of the soil, he and his coworkers made some classical advances in the knowledge in the field of soil and water conservation. As early as 1874 (7,8) Wollny studied the effect of a vegetative canopy on the structure relationship of soils. He found that vegetation protected the soil from the impact of raindrops to such an extent that the non-capillary porosity was from 34$ to 53$ higher than in unprotected soils. His results are given in Table 1. These differences were attributed to the protective effect of the leaves against the dispersive action of raindrops on the soil. The loose, granular structure of the unprotected soils was not only broken down to cause a compaction of the soil but the non-capillary porosity was also decreased as a result of the percolation of turbid water into the large pores and a subsequent clogging up of these pores with fine particles. In 1879 (9) he found that the volume decrease of a cultivated soil was related to the density of the vegetation and the rapidity with which a vegetative canopy was established. Results of this investigation are given in Table 2. He concluded that the major effect of vegetation upon the properties of the soil is due to the protective influence of the canopy against the impact of raindrops.