Assessment of the soil organic matter and ironoxides impact to aggregation

Soil organic matter, oxides, sesquioxides and clay mineralogy play the important role in aggregate formation. Since it is of necessity to investigate the behaviours of these active agents with relation of aggregates in order to improve and maintain soil quality and productivity, we evaluated soil organic matter and iron oxides impact to aggregation in the Rendzic Leptosol (locatity – Nitra–Dražovce – experiment with different soil management practices, established in 2006).There were evaluated following treatments: 1. TTP as control, 2. O (intensive cultivation of vineyard), 3. O + MH (farmyard manure – dose 40 t·ha–1), 4. NPK3 (3rd intensity of fertilization for vineyards), and 5. NPK1 (1st intensity of fertilization for vineyards). The soil samples were taken above mentioned treatments in spring 2012. Obtained results showed that, in O + MH and in NPK1 the values of labile carbon (CL) and hot–water soluble carbon (CHWD) on average increased by 668 mg·kg–1 and by 611 mg·kg–1 as well as by 53 mg·kg–1 and by 141 mg·kg–1 respectively compared to TTP treatment. Contents of total iron (Fet) and „free“ iron oxides (Fed) ranged from 19.0 to 25.9 g·kg–1 and from 4.04 to 7.16 g·kg–1 respectively. Contents of amorphous (Feo) and crystalline (Fec) iron oxides decreased in the following order: O > O+MH > TTP > NPK3 = NPK1. Intensive cultivation of vineyard had negative effect on contents water–stable macro–aggregates (WSAma ) > 2 mm. Application of NPK fertilizers significantly increased contents of WSAma > 2 mm and, on the other hand decreased content of water–stable micro–aggregates (WSAmi ). These effects were more intensive in NPK1 than in NPK3. Application of farmyard manure had also positive effects on increase of WSAma. Positive statistically significant correlations were observed between the CHK : CFK and WSAma 2 – 0.25 mm and WSAmi. All Fe forms were negative correlated with WSAma > 5 mm, however these effects were the most significant at Fed and Fec forms. Between all Fe forms and contents of WSAma 2 – 0.25 mm significant positive correlations were observed. All Fe forms (except Feo ) positive correlated with content of WSAmi.