Tomasz Sosulski

The aim of the study was to assess the impact of the specialization of agricultural production on selected parameters of soil health, i.e., soil organic carbon content (SOC), soil acidification, soil nutrient status, i.e., total nitrogen content (NT), available forms of phosphorus, potassium, and magnesium, and microelements content, as well as the content of selected potentially toxic metals (PTMs). For the study, 18 farms located in the Masovian Voivodeship in Central Poland were selected. They were grouped into six types, and each type was represented by three farms. The study included organic farms; farms specializing in: crop, vegetable, poultry, dairy cattle, and pigs production. A total of 144 soil samples were analyzed. The results showed that the specialization of agricultural production and fertilizer management had a significant impact on most of the tested soil health parameters, except SOC and NT content. Despite the high organic fertilizer doses introduced into soils in poultry (170 kg N per hectare as poultry manure) and pig farms (150 kg N per hectare as pig manure), there was no significant influence of these amendments on SOC content. This may indicate low organic carbon sequestration potential in some Polish agricultural soils. Organic farms had the lowest levels of plant nutrients in the tested soil samples, which may limit soil productivity. All the tested soils were strongly acidified, which could restrict both production and regulatory soil functions. Based on the synthetic index of soil fertility (SSFI), vegetable and poultry farms were characterized by very high fertility, while crop, dairy cattle, and pig farms fell into the medium fertility class. Organic farms were in the lowest fertility class. However, the study suggests that the SSFI may not be the best indicator for assessing soil fertility and health; therefore, further research is needed.

Two important goals of sustainable agriculture are food production and preserving and improving soil health. The soil organic carbon content is considered an indicator of soil health. The evaluation of the methods to increase the soil organic carbon content in long-term experiments is usually carried out without considering its environmental effects, (e.g., CO2–C soil emission). This study hypothesized that sandy soils have a low carbon storage potential, and that the carbon accumulation in the soil is accompanied by increased CO2–C emissions into the atmosphere. The study was carried out as a long-term fertilization experiment in Central Poland using a rye monoculture. The changes in the soil organic carbon content (SOC), CO2–C emissions from soil, and plant yields were examined for two soil treatments: one treated only with mineral fertilizers (CaNPK) and one annually fertilized with manure (Ca + M). Over the 91 years of the experiment, the SOC content of the manure-fertilized treatment increased almost two-fold, reaching 10.625 g C kg−1 in the topsoil, while the content of the SOC in the soil fertilized with CaNPK did not change (5.685 g C kg−1 in the topsoil). Unlike mineral fertilization, soil manuring reduced the plant yields by approximately 15.5–28.3% and increased the CO2–C emissions from arable land. The CO2–C emissions of the manured soil (5365.0 and 5159.2 kg CO2–C ha−1 in the first and second year of the study, respectively) were significantly higher (by 1431.9–2174.2 kg CO2–C ha−1) than those in the soils that only received mineral fertilizers (3933.1 and 2975.0 kg CO2–C ha−1 in the first and second year of the study, respectively). The results from this experiment suggest that only long-term fertilization with manure might increase the carbon storage in the sandy soil, but it is also associated with higher CO2–C emissions into the atmosphere. The replacement of mineral fertilizers with manure, predicted as a result of rising mineral fertilizer prices, will make it challenging to achieve the ambitious European goal of carbon neutrality in agriculture. The increase in CO2–C emissions due to manure fertilization of loamy sand soil in Central Poland also suggests the need to research the emissivity of organic farming.