Tillage, lime, and poultry litter effects on soil zinc, manganese, and copper

Abstract

Long‐term no‐tillage has profound effects on soil properties which can affect the availability of plant nutrient elements. The objectives were to study the effects of tillage and lime treatments on soil pH and extractable soil micronutrients where poultry litter was used as a nitrogen (N) source. Surface soil samples were taken in the spring and fall for two years from a long‐term tillage experiment that had been in place for nine years. There were two tillage treatments [conventional (CT) and no‐tillage (NT)] and six lime/ gypsum treatments (control, 8,960 kg gypsum ha‐1 every fourth year, 4,480 kg lime ha‐1 every fourth year, and three treatments of 8,960 kg lime ha‐1 in a four‐year period divided by application times into 1, 2, and 4 treatments per year). Poultry litter was applied each year of the two‐year experiment at a rate of 8.96 Mg ha‐1 on a dry weight basis. The crop was corn (Zea maize L.). Soil samples were analyzed for pH and Mehlich‐1 zinc (Zn), manganese (Mn), and copper (Cu). Soil pH was higher for NT than CT and was higher in the spring than in the fall. Lime rates resulted in soil pH increases, but showed less difference for CT than NT. The three 8,960 kg ha‐1 per four yr treatments caused an interaction in that for CT the pH increased more for 2,240 kg ha‐1each year than for 8,960 kg ha‐1 every fourth year and the opposite was true for NT. Extractable Zn, Mn, and Cu all responded to this interaction being lower for the higher pH plots. Extractable Zn was higher for NT possibly due to high Zn from the poultry litter and non‐incorporation for NT. Extractable Cu was lower for NT as expected from the soil pH, whereas extractable Mn was not affected by tillage. Extractable Zn and Cu both increased over time due to inputs from the poultry litter. Neither extractable Zn nor Mn responded to increasing lime rates, however Cu decreased with increasing lime rate. Extractable Cu was influenced mainly by soil pH differences due to tillage and lime. Extractable Zn was influenced much more by tillage and from inputs by the poultry litter and not as much by pH differences. Extractable Mn was the least responsive to tillage and lime treatments of the three micronutrients studied.