Relative Structural Developments and Crop Yields in Two Landforms of an Ultisol in Southeastern Nigeria

Aggregate stability is an important factor in the functioning of soil due to its ability to controlling plant growth, influence on root penetration, soil temperature, and water transport and seedling emergence. Some soil characteristics play important role in improving soil aggregation and hence soil structure. This study evaluated the aggregates between soils of Beach Ridge Sand (BRS) and Coastal Plain Sand (CPS) as well as relating the stable aggregates to variability in soil properties and crop yields. Twelve soil profiles were sunk for the study. The relationship between structural indices; Mean weight diameter (MWD) and Water-stable aggregate from one side and some soil properties on the other side were assessed to compare the relative stable aggregates between the landforms. Structural development of CPS improved maize yield by 67.5 % and cassava 35.3 %. However, significant difference in the aggregate stability between the two landforms was a function of organic C and hydrated Fe oxides. Differences in sand and silt content are not a probable cause of differences in aggregation of these landforms, because these particles usually have low-activity surfaces and very low surface areas compared with clay particles. Calcium contents also influence aggregation, but do not correlate well with any of the aggregation indices in these landforms.