Saturday, 15 July 2006

Structural Aggregates' Stability in Soils Irrigated with Sodic-Saline Water and Subsequently Reclaimed.

Giovanna Cucci, Angelo Caliandro, and Giovanni Lacolla. Università di Bari - Dipartimento di Scienze delle Produzioni Vegetali, Via Amendola 165/a, Bari, 70126, Italy

The soil structure degradation largely depends on irrigation water quality, soil particle-size and type of clay minerals. The objective of the research was to assess the stability of the structural aggregates of two soil types first submitted to a four-year irrigation with 9 types of sodic-saline water obtained by dissolving in de-ionised water adequate amounts of NaCl and CaCl2, and then reclaimed for two years through the application of adequate amounts of CaSO4 2H2O and leaching water. The research was conducted at the Campus of the Agricultural Faculty of Bari (Italy). The two types of soil, sampled from the horizon AP, were the following: T1) Udertic Ustochrept, Montefalcone series (Bologna – Italy) andT2) Pachic Hoploxeroll, Cutino series (Locorotondo - Bari). The soil T1 is characterised by the predominance of vermiculite and illite and a low amount of Fe and Al sesquioxides, whereas in T2 illite and kaolinite are prevailing with large amounts of Fe and Al sesquioxides. On the soil samples, taken along the whole profile both at the end of the four-year irrigation with sodic-saline water and after the two-year reclamation, the structural aggregate stability was tested on the aggregates of 1 to 2 mm in size and using the water sieving method. For both soil types, notably for T1, the structural stability indices obtained have shown a significant reduction with the increasing salinity and sodium index of the irrigation water applied in the previous four years. The reclamation techniques applied for two years have induced an improvement in the structure stability indices by 9.5% and 3% respectively for soils T1 and T2. Key words: soil structure stability; salt concentration and soil structure; SAR and soil structure.

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