Agrochemical characteristics of Haplic Chernozems in conventional and transition to organic farming
Margarita Nankova • Atanas Atanasov • Iliya Iliev
Dobrudzha Agricultural Institute – General Toshevo, 9521, General Toshevo, Bulgaria
Резюме
The research was carried out in 4-field crop rotation in the experimental field (Haplic Chernozems) of Dobrudzha Agricultural Institute – General Toshevo. The study covers the period 2018-2020. Agrochemical analyzes characterize two systems of agricultural farming - transition to organic farming (TOF) and conventional one (CF).
The nutrition regime in conventional part of the trail was differentiated by using mineral fertilization with variable nitrogen norms - from 0 to 180 kg N/ha against background fertilization with 60 kg P2O5/ha and 60 kg K2O/ha.
After nearly four years period of transition to organic farming statistically significant differences in soil pH values were found between organic and conventional systems. The transition to organic farming keeps the level of the soil reaction close to neutral without a significant difference between its values in layers 0-20 cm and 20-40 cm. Annual application of nitrogen fertilizaion, especially with 180 kg N/ha lead to the lowest value of this indicator in the depth to 40 cm.
The forms of mineral nitrogen and their total amount are reliably influenced by the meteorological conditions during the years of research. It has been found that over 60% of mineral nitrogen is in nitrate form. In all variants of conventional farming there is a clear reduction of mineral nitrogen in the underlying layer, while in the transition to organic farming its content is maintained at the level of the surface layer.
Over the years, the variation in the values of available phosphorus at the studied depths is from 2.31 mg P2O5/100 g soil to 17.76 mg P2O5/100 g soil depending on the type of variant. As commented above, these changes are statistically significant and the scattering of the trait is large.
In the conventional farming system, the annual nitrogen fertilization with increasing norms against the background of PK leads to enrichment of the upper part of the root layer with available phosphorus.
At this stage, no statistically significant differences were found in the content of exchanged potassium in the transition to organic farming and the variants of conventional production with lower fertilizer norms. In the variant with annually nitrogen fertilization (N180P60K60) there is a tendency to enrich the two soil layers not only with available phosphorus, but also with cation-exchanged potassium.
A statistically significant negative correlation was found between the soil reaction and the sum of forms of mineral nitrogen and available phosphorus. The correlations are positive. Almost all correlations of cation exchange potassium with other indicators are statistically insignificant.
Despite the relatively short period of transition to organic farming, changes in the content of available for plants forms of nitrogen, phosphorus and potassium have been found. This transition period has had a particularly favorable effect on soil acidity.
