engleski

Changes in Soil Properties after 15 Years of Different N Fertilization

After establishment of the experimental field (1996) with different nitrogen fertilization practices for arable crops, we have analyzed influence of different treatments on selected soil properties. Included treatments are 1. Control, without any fertilization, 2. N0PK, 3. N100PK, 4. N150PK, 5. N200PK, 6. N250PK and 7. N300PK. Fertilization with phosphorus and potassium was equal for all trial treatments in the same year of investigation, excluding check treatment. Research was conducted on experimental field located within drained cropland in Western Pannonian subregion of Croatia (45°33´N, 16°31´E). The soil type of trial site is drained distric Stagnosols. Terrain is flat with average altitude 97.2 m. Groundwater occurs under 175 cm below soil surface. Besides soil physical properties that favor water stagnation in upper layers, and low soil organic matter content, the main factor that limits crop yield is low soil pH value. We have recorded changes in soil pH, and in soil content of plant available P2O5 and K2O, total C content, total N content in soil. In order to get good spatial distribution, during summer 2010 we have used new way of soil sampling with increased volume of sampled soil, and with high density of sampling. Semi-automatic circular tractor soil probe prototype (PCT-HR2011-000021) was tested after winter wheat harvest (20th July, 2010). Sampling was performed with grid sampling in a grid of 15 x 15 m, at grid intersections. In soil samples pH was determined in 1:2.5 (w/v) in (1 M KCl) soil suspension (modified ISO 10390). For soil P2O5 and K2O content determination we have used AL method (soil extraction by ammonium-lactate solution) which is the most common method for this type of analyses in Croatia. Total carbon and nitrogen content were determined by dry combustion method (elemental analysis) with the Vario Macro CHNS analyzer (Elementar). Different mineral nitrogen fertilization was found to be the key factor that influenced soil pH 15 years later, with decreasing values corresponding with the increased N levels. Changes in P2O5 and K2O were significant, after 15 years of continuous fertilization, compared to the original state at the time of the beginning of experiment. We have recorded higher average total nitrogen content in soil at the treatments with higher nitrogen fertilization rates. We have also concluded that nitrogen fertilization has influenced the increase in total soil carbon content.

Soil ; Nitrogen fertilization ; Spatial variability

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