The number of growing seasons required for no-till practices to improve soil properties should be considered before changing management systems. To evaluate this time factor, an 8-yr tillage study was conducted on a Grenada silt loam (fine-silty, mixed, active, thermic Glossic Fragiudalfs) using cotton (Gossypium hirsutum L.), grain sorghum [Sorghum bicolor (L.) Moench]-corn (Zea mays L.), and soybean [Glycine max (L.) Merr.]-wheat (Triticum aestivum L.) as test crops. Soil samples were characterized for soil organic matter (SOM), pH, exchangeable Ca and Mg, extractable P, K, Fe, Mn, Cu, and Zn, aggregate stability (AS), water dispersible clay (WDC), total clay (TC), and modulus of rupture (MR) at time 0, 4, and 8 yr. Within 4 yr, no-till (NT) resulted in statistically significant (P less than or equal to 0.05) differences compared to conventional tillage (CT). The surface 2.5 cm of the NT treatments had higher levels of SOM, exchangeable Ca, and extractable P, Mn, and Zn, but lower extractable K, Fe, and Cu. Tillage had no effect on exchangeable Mg and pH. No-till also resulted in higher AS, and lower MR, WDC, and TC in the top 2.5 cm, relative to CT. The differences in soil properties between tillage treatments were essentially independent of crop. Instead, the results are controlled by relative amounts of SOM and clay, and the extent to which these properties change with time. Undoubtedly, NT practices ran improve several fertility and erodibility-related properties of this soil within 4 yr, and-enhance its sustainability.
