# Developmental History of Soil Concepts from a Scientific Perspective
## 4 Discussion  
### The Emergence of Soil Concepts  
Many soil concepts have emerged at different times over the years. The soil fertility concept appeared to be the earliest of all of the soil concepts examined in both all journals (1908) and soil science journals (1917) (Tables 4 and 5). [PERSON] (1977) argued that much of the research that contributed to progress in soil fertility research was conducted even before the establishment of a formalized soil science [21]. [PERSON] and [PERSON] (2004) supported this idea and asserted that the oldest writing on the topic--the book _Yugong_, which described the characteristics of soil fertility in Northern China--appeared in around 500 B.C.E. [22]. The soil fertility concept has a strong association with measurements of soil nutrients for crop production [23]. [PERSON] (2004) found the historical linkage between human fertility and soil fertility in the writing--_Mother Earth_(24,25). The linkage has been developed across diverse cultures as farmers developed a general agronomic theory in the late 18 th century [26]. Social and technological development and understanding have also impacted the development of soil concepts. Food supply shortages during and after the World Wars led questions of soil fertility to be central [22] at a time when urgent demand for farm products and high prices confronted U.S. farmers [27]. Many countries in Europe also recognized the need to increase agricultural production, especially after World War II [28]. [PERSON] and [PERSON] were early scientists in Europe who contributed to the initial development of organic chemistry for soils and mineral fertilizer production, which revolutionized agricultural production. A German chemist, [PERSON], later synthesized and industrialized nitrogen fertilizers, which coincided with trends to industrialize and corporatize agriculture and forest industries (e.g., machinery- and technology-derived agricultural revolutions). Land reform after World War II, enforced by U.S. occupation forces, also played an essential role in consolidating fragmented agricultural land in Japan [29]. Other countries in South Asia have increased external inputs to enhance agricultural production by diversifying biophysical and chemical conditions. Soil fertility currently emphasizes the biological, chemical, and physical soil attributes important for provisioning crop nutrients and water [30,31]. The measurements and analysis of such soil properties have been explored as well in context of soil fertility studies, e.g., [32,33]. The concepts of soil conservation and soil productivity appeared in soil science journals at almost the same time in the late 1940s (Table 4). The first author found in the search process for all journals in the Web of Science was [PERSON] (1926), who argued that soil conservation should deal with both plant-food ingredients and the ability of the soil to attain maximum crop production capability under all environmental conditions [34]. The change point for the soil conservation concept came about 20 years later with [PERSON] and [PERSON]'s (1948) article, published in SS [35]. [PERSON] (2012) reported that many U.S. Plains areas had cumulatively lost more than 75% of their original topsoil due to deep ploving and drought, which was notably visible by the 1940s [36]. [PERSON] (1974), argued that the origin of the U.S. national soil conservation program occurred much earlier than the U.S. Dust Bowl era of the 1930s [37]. The author stated that an article he wrote, which was published by the Department of Agriculture in the 1920s, was the first comprehensive appraisal of the erosion issue in the U.S. Many regional erosion stations were built and thousands of soil and water measurements were performed to comply with the Buchanan Amendment to the Agricultural Appropriations Bill for 1930. [PERSON] argued that the commitment of scientists to prevent nutrient runoff and soil erosion was undertaken at the national level using a top-down approach.