Aggregate composition and stability of structural aggregates of non-calcareous rendzinas in Eastern Serbia

Abstract

The present study includes the results of comparative investigations of aggregate composition and water stability of structural aggregates in humus horizons of non-calcareous rendzina under native forest and pasture vegetations and the same rendzina utilized long-term as arable field. The results show that aggregate composition and water stability of structural aggregates in the cultivated non-calcareous rendzina are significantly impaired due to a long-term anthropogenization. In the cultivated rendzinas the content of agronomically most valuable aggregates (0.25-10 mm) significantly decreased, while the percentage of cloddy aggregates (>10 mm) was increased about 1.5 to 3.5 times in comparison with the rendzina under pasture and forest vegetations. The structure coefficient of cultivated soils was lower (2.61) than in forest (4.63) and pasture (10.47) rendzinas. The cultivated non-calcareous rendzina had lower (59.12%) aggregate water stability than rendzina under pasture (82.66%) and forest (91.92%). Mean weight diameters of water stable agregates was higher in forest (1.44 mm) and pasture (1.20 mm) than in cultivated (0.65 mm) rendzina.

U ovom radu je dat prikaz uporednih istraživanja agregatnog sastava i vodootpornosti strukturnih agregata u humusnom horizontu beskarbonatnih, skeletnih, praškasto-glinovito ilovastih rendzina na laporcu i laporovitim krečnjacima, pod prirodnom šumskom i pašnjačkom vegetacijom, i istih rendzina koje se dugotrajno (vekovima) koriste kao njivska zemljišta u istočnoj Srbiji. Dugogodišnja antropogenizacije dovela je do znatnog pogoršanja agregatnog sastav i vodootpornosti strukturnih agregata. Međutim, i pored toga, njivske rendzine se, prema klasifikaciji koju navode Shein et al. (2001), još uvek karakterišu dobrim agregatnim sastavom. U njivskim rendzinama sadržaj agronomski najpovoljnijih agregata (prečnika 0.25-10 mm) je znatno smanjen, dok je udeo (prošek 26.15%) grudvastih agregata (prečnika >10 mm) znatno povećan u poređenju sa šumom (17.00%) i pašnjakom (6.92%). U humusnom horizontu istraženih beskarbonatnih rendzina pod šumom i pašnjakom utvrđena je znatno veća vodootpornost strukturnih agregata nego u njivskoj rendzini. Najmanju vodootpornost pokazali su strukturni agregati prečnika >3 mm. Koeficijent strukturnosti u njivskoj redndzini znatno je manji nego pod šumom i pašnjakom. Najveći prosečni prečnik strukturnih agregata (MWD) u suvom stanju utvrđen je u rendzinama pod šumom (5.24 mm). 4.41 mm pod pašnjakom i 4.20 mm u njivskoj rendzini. MWD vodootpornih strukturnih agregata veći je za oko 2 puta u zemljištu pod pašnjakom (l .20 mm) i pod šumom (1.44 mm) nego u njivskoj (0.65 mm) beskarbonatnoj rendzini.