Structural quality of a Latosol cultivated with oilseed in succession to soybean

Understanding the changes in soil structure that develop from oilseed crop successions is vital for successful production. The objective of this study was to evaluate the effects of different oleaginous crop successions on the least limiting water range and load-bearing capacity of a clayey Rhodic Hapludox. The following oilseed crops were cultivated under a no-tillage system in autumn-winter: sunflower (Helianthus annuus L.), canola (Brassica napus L. and Brassica rapa), safflower (Carthamus tinctorius L.), crambe (Crambe abyssinica Hochst.) and niger seed (Guizotia abyssinica). They were sown after soybean and soybean/corn (summer/fall-winter). When the autumn-winter crops flowered, soil samples with structure intact were collected at the 0.0–0.5 m and 0.5–0.10 m depths in metal cylinders. It was observed that in terms of water interval, the poorest soil structural quality in the 0.0–0.5 m layer was provided by the corn/safflower and corn/crambe successions. In terms of soil water content, the optimal time for soil management practices varied for the different oilseeds succeeding soybean. Soil load capacity varies inversely with water content and directly with soil density. Niger grown during autumn-winter in succession to soybean improved Rhodic Hapludox structure more than the other crop successions.