Black Soil Characteristics and Constraints
The soils developed on schists and gneisses and are moderately shallow (50-75 cm) to moderately deep (75-100 cm) where as those developed on basalt are deep (100-150 cm) to very deep (>150 cm). These soils are highly argillaceous with clay content varying from 30-80%.
The clay of Black soil has high coefficient of expansion and contraction, it is dominantly smectitic in nature, which leads to the development of typical features such as gilgai micro-relief, deep and wide cracks and closely intersecting slicken sides.
The members developed on calcareous clay parent material have high CaCO3 content that increases irregularly with depth. Black soils have pH values ranging from 7.8 to 8.7, which may reach up to 9.4 in sodic soils.
Black soils have cation exchange capacity (35-55 c mol (p+) kg -1) and it is rich in base status. The black soils also have high moisture holding capacity (150-250 mm/m), yet water is not available to plants because the water is held tenaciously by the smectitic clay.
Black soils are extremely sticky when wet and extremely hard when dry. It have low permeability and the bulk density of these soils is generally high (1.5 to 1.8 Mg m -3) because of it is shrink when it dry.
Black soils suffer from moisture stress during drought. These soils are poor in organic carbon, nitrogen, sulfur and phosphorus. Water holding capacity is a major problem in shallow soils. Whereas deep soils when irrigated are very much prone to salinity and sodicity particularly in the subsoil.