Influence of cropping, manure, and manure plus lime on exchange capacity, exchangeable calcium, pH, oxidizable material, and nitrogen of a fine-textured soil in eastern Nebraska

Soil samples were taken from the Nebraska soil fertility plots at the time of establishment (1921) and at the end of a 16-year rotation period (1936). Included in the work reported here were samples from the surface 6 inches of plots treated with manure and with manure plus lime, as well as those from adjacent check plots. All samples were analyzed after 1936. Analyses made on these samples included exchange capacity, exchangeable calcium, pH, oxidizable material, and nitrogen. Results of the study may be summarized as follows: 1. In the surface 6 inches of the check plots, 16 years of cropping resulted in small but not statistically significant decreases in exchange capacity and content of exchangeable calcium. The pH values, the content of oxidizable material, and the content of nitrogen had decreased significantly. 2. Differences between the manured and check plots in exchange capacity and content of exchangeable calcium were not statistically significant. A barely significant difference in the pH value was found. Significant differences between these plots were found for the content of oxidizable material and of nitrogen. 3. As compared with the check plots, those receiving manure plus lime did not exhibit a statistically significant difference in the exchange capacity. The difference between these plots in content of oxidizable material was just below the level of significance, whereas the difference in content of nitrogen was barely significant. However, marked differences (statistically highly significant) were found between these plots in the content of exchangeable calcium and in the pH values. The check plots had a pH of 5.5 and were 57% saturated by exchangeable calcium; those receiving manure plus lime had a pH of 6.9 and were 72% saturated by exchangeable calcium.