Impact of Soil Tillage and Crop Rotation on Barley (Hordeum vulgare) and Weeds in a Semi-arid Environment

Experiments were conducted to evaluate the effect of mouldboard‐ or chisel‐ploughing and rotations on barley crops and associated weeds in a semi‐arid location. Two primary soil tillage operations and eight crop rotation‐tillage operation combinations were evaluated over two successive seasons. Drought conditions prevailed (<152 mm annual precipitation) and affected the measured parameters. Barley grown in mouldboard‐ploughed plots had higher biomass compared with chisel‐ploughed plots. Barley grain yield was greater in mouldboard‐ploughed plots in a fallow‐fallow‐barley rotation. Weed species densities varied between tillage systems and rotations. Density of Hordeum marinum, for example, was high in fallow‐barley‐fallow in chisel‐ploughed plots, and was high under more continuous fallow in mouldboard‐ploughed plots. Similar variations were also observed in weed fresh weights and in numbers of seed produced. The results describe the productivity of barley under extremely dry conditions, where an advantage for mouldboard ploughing was observed. The results also indicate the complexity of weed communities in their response towards different tillage‐rotation combinations.     

Effects of Reduced Tillage and Fertilization Practices on Soil Characteristics, Plant Water Status, Growth and Yield of Upland Cotton

Three different tillage practices, conventional (mouldboard ploughing at 22–25 cm plus one rotary hoeing at 5–6 cm, CT), minimum (one rotary hoeing at 12–15 cm, MT), and no‐tillage (direct drilling in soil covered by vetch residues, NT), combined with three fertilization treatments, inorganic (50 kg N ha^?1 as ammonium sulphate), cattle manuring (30 t ha^?1), and control (no‐fertilizer), were applied on a cotton crop (Gossypium hirsutum L. cv. Acala SJ‐2) grown on a clay loam soil in the field of the Agricultural University of Athens. Soil (gravimetric water content, bulk density, and penetration resistance in the top 40 cm) and plant parameters (root growth, leaf water potential, leaf area growth and seedcotton yield) were recorded throughout the cultivation period in all treatments. No‐tillage was associated with significantly higher values of soil water throughout the observation period caused by the vetch mulch. Bulk density and penetration resistance were initially higher in the no‐tilled plots, but they became significantly lower after 2–3 months from sowing. These beneficial effects on soil properties favoured root growth, expressed as root surface density, in the NT‐plots at the top soil layer. Similar, although less spectacular, effects were observed in the manured plots. Plant water status, expressed in terms of the water potential index, was significantly and consistently best in the NT‐ and worst in the CT‐plots throughout crop growth. In addition, NT favoured a better foliage growth and resulted in significantly higher yields than the other tillage practices. In general, NT, and in second instance, MT considerably improved plant water status, and hence foliage growth and yield in comparison with CT by maintaining higher levels of soil water and improving root growth. Manuring positively interacted with the reduced tillage practices for most soil and plant parameters.