Cumulative effects of pig slurry application on soil chemical properties under semiarid conditions, Toledo, Spain

The effect of the consecutive addition of pig slurry at rates of 0 (control), 30, 60, 90, 120 or 150 m(3) ha(-1) yr(-1) over a 4-year period, on sol I chemical properties and macro and micronutrients contents, was investigated in a field plot experiment under semiarid conditions. The control soil had a slightly acidic pH, a low electrical conductivity (EC), an adequate level of N for barley growth and low contents of total organic C or available P and K. With respect to the control soil, the pig slurry-amended soils had higher pH, EC, available P and K and slightly larger total N contents. A decrease of total organic C was observed only in soils amended with pig slurry for 4 years at a rate of 150 m(3) ha(-1) yr(-1). With respect to the control soil, the pig slurry-amended soils had greater total contents of Mn, Zn and Cu, and similar total Fe concentrations. The available Fe and Mn contents were generally lower in amended soils than in the control and tend to decrease with the increase of the slurry rate, whereas it was just the opposite for Zn and Cu.