The state of soils was presented in the aspect of environmental protection when using acidified slurry was used as fertilizer to protect ammonia from escaping into the atmosphere. The use of concentrated sulfuric acid to lower the pH of the slurry and thus retain nitrogen in the soil and then use it by crops gives a double benefit, reduces nitrogen losses, and reduces the cost of mineral fertilizers that should be purchased. Injecting raw slurry below the surface of the soil has some benefits in the form of reducing ammonia emissions, but it does not affect the use of fertilizers with the addition of sulfur, which is ensured in the case of acidification of the slurry. Additional benefit is to obtain environment protection. Leaching of elements from grassland and corn crop soil treated with raw cattle slurry and acidified cattle slurry (m3·ha−1) was presented. The K content was highest in the leachate collected after the application of the last batch of acidified slurry. Yield tests were conducted on similar soils as presented in the tables for grass, using six 500 m2 plots with corn, cultivar ES Cirrus, with acidified slurry and one test plot with non-acidified slurry. Analysis of variance and significant difference among the treatment means were separated using Duncan’s Multiple Range Test (DMRT) at a probability level of 0.05. Based on statistical analysis, it was demonstrated that crop yields of corn grain increased when fertilized with acidified slurry, at an average of 4 t·ha−1. During field tests corn crop yield varied from 14 t·ha−1 to 18 t·ha−1 when non-acidified and acidified slurry were used. The yield on the grassland was approx. 30 t·ha−1. The soil sorption complex, in combination with its buffer properties and acidification, did not affected the pH value. This makes the acidification process safe for plants and for the soil environment.