ACID-BASE BUFERING OF SOILS IN CONNECTION WITH THEIR AGROGENIC ACIDIFICATION AT TEA CULTIVATION IN THE SUBTROPICS OF RUSSIA

Abstract

Based on long experience with fertilizers on tea culture in the conditions of the Sochi Black Sea coast, the buffer properties of brown forest acid soils, acidified in various degrees as a result of the use of single (111), double (222) and triple (333) doses of NPK were studied. The total load of nitrogen fertilizers (the main factor of acidification) for 26 years of use was 3.8-7.6-11.4 tons N/ha. Comparison was made with the soil without fertilizers (000) and forest soil. The identical capacity of soil buffering relative to the hydroxyl load was revealed: shift by 1 and 2 pH units with the introduction of 2.5 and 10.0 mEq NaOH per 100 g of soil. Soil resistance to acid loads was increasing in the series: forest — 000 — 111 — 222 — 333. The highest buffer capacity under increasing proton load was found in soils with a high degree of acidification as a result of the use of double and triple doses of NPK. For them, a shift of 2 pH units was achieved by adding into the suspension about 12.5 mEq HCl per 100 g of soil, while for others it was about 7.5 mEq HCl per 100 g of soil. The resistance of some soils (222 and 333) to acid loads was higher than to alkaline loads, while the resistance of others (forest, 000, 111) on the contrary.