Effect of irrigation on soil structure and water stability of aggregates

Abstract

The paper presents the results of comparative investigations of structuration degree, macro- and microaggregate stability of irrigated and non-irrigated type of carbonate clayey chernozem and non-carbonate clayey humogley soils within watering system in Surcin ( in the vicinity of Belgrade), where watering by sprinkling is carried out for more than 10 years. Due to the sprinkling, there occurred a degradation of the surface part (0-10 cm) of arable horizons, the aggregates of which are destructed by rain drops to a significant degree. The aggregates with the diameter of 10-5 mm are especially exposed to this process. The content of lumpy (>10 mm) aggregates in deeper parts (10-30 cm) of the arable horizon in the irrigated soils is significantly higher than in non-irrigated ones, while the ratio of agronomically most favorable aggregates (10- 0.25 mm) decreases, the decrease being much greater in chernozem than in the humogley soil. Under the influence of several years of sprinkling, the resistance of the structural aggregates to water of the investigated soils is also decreased, the lowest water resistance being present in the aggregates >3 mm of the surface part of the arable horizon. Several years of irrigation by sprinkling led to a degradation of microaggregate composition of the chernozem. However, in the irrigated humogley soil, microaggregates are more water resistant than in the non-irrigated one, which is supported by the data on the aggregation degree.

U ovom radu prikazani su rezultati uporednih istraživanja strukturnog stanja, makro i mikroagregatne stabilnosti navodnjavane i nenavodnjavane varijante karbonatnog ilovastog černozema i beskarbonatne glinovite ritske crnice u zalivnom sistemu u Surčinu (okolina Beograda), gde se zalivanje kišenjem vrši duže od 10 godina. Usled kišenja znatno je pogoršan agregatni sastav površinskog dela (0-10 cm) omičnog horizonata, čiji agregati su u znatnom stepenu razoreni kišnim kapima. Tom procesu su naročito izloženi agregati dijametra 10-5 mm. Sadržaj grudvastih (>10 mm) agregata u dubljim delovima (10-30 cm) orničnog horizonta u navodnjavanim zemljištima je znatno veći nego u nenavodnjavanim, dok se udeo agronomski najpovoljnijih agregata (10-0.25 mm) smanjuje, i to mnogo više kod černozema nego kod ritske crnice. Pod uticajem višegodišnjeg kišenja smanjena je i vodootpornost strukturnih agregata istraženih zemljišta, pri čemu najmanju vodootpornost pokazuju agregati >3 mm u površinskom delu orničnog horizonta. Višegodišnje navodnjavanje kišenjem dovelo je do pogoršavanja mikroagregatnog sastava černozema. Međutim, u navodnjavanoj ritskoj crnici mikroagregati su vodootporniji nego u nenavodnjavanoj, o čemu svedoče podaci o stepenu agregatnosti.