The influence of no-till, conventional tillage and nitrogen fertilization on physico-chemical and biological indicators after three years of monoculture barley

An experimental trial was carried out over three years at Cavacurta (Po valley, Italy) on continuous barley. The soil was a coarse-loamy over sandy, mixed, mesic Fluventic Ustochrept. The experimental design was a split-plot with four replicates; the main factor was the soil management system (conventional tillage, CT, and no-tillage, NT), while the secondary factor was the nitrogen fertilization (N0 = 0, N1 = 50 and N2 = 90 kg N ha-1 year-1). At the end of the third year soil samples were taken in all plots at four depths (0-5, 5-10, 10-15 and 15-20 cm). For these samples, pH, organic matter, total N, available P and cation exchange capacity were determined. On the contrary, water aggregate stability was determined for a single layer (0-20 cm depth), excluding the N1 level of fertilization. The biological indicator, QBS-ar index, was studied only in the layer 0-10 cm. Statistical analysis shows that no-till positively influenced all the indices except for CEC and QBS-ar. N fertilization had significant effects on CEC only; in the upper layer, the value in N2 subplots was of approx. 1 cmol+ kg-1 higher than in N0 and N1 subplots. There was no significant interaction for any of the indices. As regards only the 0-20 cm layer, the most important results are as follows. The organic matter content in NT plots was significantly higher than in CT plots (32.6 vs 29.8 g kg-1), as was the total N (2.11 vs 1.97 g kg-1). No-till also had a very clear effect on the Olsen-P (12.3 vs 9.3 mg kg-1). The most remarkable result was found for the water aggregate stability: for NT plots the value was 246% higher than for CT plots (34.3 vs 9.9%). As regards the microarthropod community, the value of the QBS-ar index was between 90 and 126, a typical range for soil under barley.