The Influence of No-Till, Conventional Tillage and Nitrogen Fertilization on Physico-Chemical and Biological Indicators After Three Years of Monoculture Barley

Abstract

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.