The objective of the study was to assess the effects of long-term application of liquid manure from pig production and digestate from manure fermentation installation for biogas production on chemical changes in the soil, i.e.: soil reaction, accumulation of available forms of phosphorus, potassium, and magnesium in the soil arable layer, as well as the phosphorus balance. The assessment was carried out in two highly productive farms specialising in pig production, located in the Zachodniopomorskie Province. The soils under the study were treated with slurry and digestate annually for subsequent 12 years. The assessment of changes in nutrient content and accumulation was performed twice: after 10 and 12 years of fertiliser treatments. The rate of changes in soil reaction due to slurry and digestate application varied depending on the analysed field. Irrespective of the analysed field, 12-year application of slurry caused a drop in soil pH by an average of half a unit. The direction of changes in the content of available nutrient forms in the soil varied depending on the element evaluated. Notwithstanding the analysed field and the type of slurry used, a decrease in the content of available forms of potassium in the soil was observed. Slurry fertilisation did not affect magnesium contents in the soil. In the study period, the content of magnesium remained unchanged. Among the evaluated nutrients, an increased nutrient content in the soil was only found in the case of phosphorus – as a result of application of liquid manure in combination with mineral fertilisation. In the analysed farms, in the case of fields fertilised with slurry and digestate, the phosphorus balance was positive, and ranged from 15 to 40 kg P·ha−1. The obtained values of the phosphorous balance strongly suggest that regardless of the type of liquid manure used on the farm, measures should be taken to introduce changes in the scope of fertilisation plans, with particular emphasis on the principles of balanced fertilisation.
The paper demonstrates the influence of different mineral fertilization with phosphorus and potassium on the concentration of copper (Cu) and manganese (Mn) in the ear leaf of maize at the stage of flowering (BBCH 65) as well as the contents and accumulation of the nutrients studied in maize when fully ripe (BBCH 89). A single factor experiment was carried out in 5-year-cycle (2007-2011), in the randomized complete block design. The experiment was conducted as a part of a long-term stationary trial. The investigation comprised 8 different P and K treatments: the absolute control, exclusive of one of the main nutrients (P - WPN or K - WKN), reduced amount of phosphorus and potassium (to 25% - W25 and to 50% WP50, WK50) as well as recommended amounts of basic nutrients (NPKMg - W100 and NP*KMg, P* - P* as PAPR - W100 PAPR). Evaluation of the nutriational status, performed in the ear leaf of maize at flowering stage, showed that regardless of fertilization treatment applied, the concentration of copper was lower than normative values, whereas that of manganese ranged within the optimal scope. At the same time, there was found a significant relationship between the grain yield obtained and acquisition of both copper and manganese by maize at flowering stage (stronger for manganese, r = 0.614). The total accumulation of copper and manganese in fully ripe maize was significantly differentiated as a result of mineral fertilization. The total uptake of Cu and Mn was reduced under the conditions of 10-year lack of P fertilization. Uptake reduction was considerably more advanced when K fertilization was absent for 10 years. Regardless of the experimental factor effects, more than 50% of the total copper uptake was accumulated in grain, whereas the majority of manganese was accumulated in maize leaves (50-64% of the total uptake). Correlation analysis showed a significant relationship between maize grain yield and the total accumulation of copper, whereas that of manganese was observed only in 3 of 8 treatments tested (WPN, WP50 and W100 as PAPR).