Phosphorous in air-dry soil aggregates of Chernozem in different types of human-induced landscapes (Kursk region)

Phosphorous is one of the most important elements for plant life, its supply is limited, so supporting the balance of phosphorous is considered to be a global challenge for the 21^st century[1]. In the majority of soils, a vast amount of organic and mineral phosphorous is contained in immobile and insoluble compounds. Intensive tillage, even without fertilizers, may provide plants with resupply of phosphorous, but it leads to negative ecological consequences. [2] There is large amount of total phosphorous (0,15 - 0, 35% P2O5) in Chernozem of Kursk Region, and about 50-70% of it is organic compounds. [3]

We investigated soils with different land use: mowed grassland, soil under the wood line, soil of perennial fallow, tillage and no-till farming. The main soil is Vermic Chernozems (WRB).  Every soil sample was divided into four groups of different-sized aggregates (> 5 mm, 5-2 mm, 2-1 mm and < 1 mm) by Savvinov dry sieving method. We determined the content of organic carbon, mobile phosphorous, organic phosphorous, mineral phosphorous and total ratio of phosphorous and other elements in each group.

Cultivation increases the content of mobile phosphorous because of mineralization process. However, it leads to content reduction of organic matter. Moreover, it significantly changes the structure: the amount of aggregates larger than 5 mm increases. The content of mobile phosphorus in natural soil depends on the size of aggregates, and its amount decreases with decreasing size of aggregates. After cultivation, this trend changes, and mobile phosphorus is shared almost evenly among all groups of aggregates. Most of the mobile phosphorus is in the soil with no-till farming.

When the structure is damaged, the phosphoric state of the soil changes, which will lead to changes in the nutrition of plants.

Literature

1) Yang X., Chen X., Yang X., 2019. Effect of organic matter on phosphorus adsorption and desorption in a black soil from Northeast//

2)Агрохимическая характеристика почв СССР. Почвенно-агрохимическое районирование / Всесоюзная академия сельскохозяйственных наук им. В.И. Ленина (ВАСХНИЛ), Почвенный институт им. В.В. Докучаева ; Отв.ред. Андрей Васильевич Соколов, Николай Николаевич Розов . – Москва : Наука, 1976 . – 363 с.

3)Макаров М.И. Фосфор органического вещества почв. – М.: ГЕОС, МГУ, 2009. – 397