Submitted to: Soil & Tillage Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/14/1996
Publication Date: N/A
Interpretive Summary: Changes in soil-profile nutrient distributions with the adoption of conservation tillage systems could have a significant impact on the productivity and ecology of land management systems by altering (i) the quantity and timing of nutrient availability, (ii) competition between crops, weeds, pests, and soil microorganisms and fauna, and (iii) the potential for environmental degradation due to excessive nutrients entering surface and ground waters. Extractable P, K, Zn, Fe, Mn, and Cu under no tillage tended to be present in higher levels than under conventional tillage, especially near the soil surface due to surface placement of crop residues. Secondary cations of Zn, Fe, Mn, and Cu were generally greater under no tillage than under conventional tillage throughout the 0-0.3 m depth probably due to wetter, denser soil conditions. Few differences between tillage regimes occurred with soil pH, nitrate, sulfate, and extractable Ca, Mg, and Na. Continuous no tillage did not appear to have any detrimental effect on soil-profile nutrient distributions, and in the case of extractable P and K especially, was beneficial by allowing accumulation near the soil surface where plant roots are most active.
Technical Abstract: Nutrient distributions under no tillage (NT) compared with conventional tillage (CT) management need to be assessed so that future placement, quantity, and types of fertilizers can be altered, if necessary, to efficiently match crop demands. We determined soil-profile distributions of pH, N, P, S, K, Ca, Mg, Na, Zn, Fe, Mn, and Cu to a depth of 0.9 m at the end of 8.5 yr of continuous CT and NT management on a Weswood silty clay loam (fine, mixed, thermic Fluventic Ustochrept) in southcentral Texas. Most dramatic changes occurred within the 0-0.05 m depth, where soil under NT had lower pH, Fe, and Cu than under CT, but greater P, K, Zn, and Mn. Greater P and K under NT than under CT also occurred below the till-zone (0.15-0.3 m). At a depth of 0-0.3 m, soil under NT contained greater amounts of extractable P, K, Zn, Fe, Mn, and Cu than under CT. Nitrogen fertilization had little effect on nutrient distributions, except producing greater extractable K at 0-0.05 m and greater nitrate at 0-0.15 m. Few changes in soil-profile distributions were observed for extractable S, Ca, Mg, and Na. Long-term continuous use of NT enhanced conservation and availability of P, K, Zn, Fe, Mn, and Cu near the soil surface where crop roots proliferate.