Shoot and root growth of cereals under reduced tillage in Organic Farming in field trials in Germany and Greece

Summary

In two organically cultivated field trials, located in Germany and Greece, effects of reduced primary tillage systems on root and shoot growth of cereals were investigated. The field trial in Rommersheim near Mainz, Germany, was established in 1994. A similar experiment was established in 1995 located in Athens, Greece. Mouldboard plough, two-layer plough and layer cultivator were used in Germany. Mouldboard plough, rotary hoe and zero tillage were applied in Greece. The field experiment in Germany was performed on a clay loam soil with a 5-year crop rotation (green fallow, winter wheat/catch crop, peas, winter rye/catch crop, spring barley) in a split-plot design. The investigated crop was spring barley and winter rye. Tillage systems were implemented after cereal harvests only. The field experiment in Greece was performed on a clay loam soil with a 3-year crop rotation (cereal, green manure, cotton) and a split-plot design. The test crop was winter wheat. The parameters measured in both field trials were soil physical and chemical parameters, as well as root and shoot parameters of the cereals.
In Germany higher tillage intensity implemented on spring barley on one hand reduced aggregate stability and decreased the penetration resistant, especially in lower depths. On the other hand, it increased rooting density, nutrient uptake and crop development. Dry matter production of weeds was significantly lower in the ploughed fields compared with those treated with the cultivator. Correspondingly, higher grain yields were positively correlated with tillage intensity. Positive effects of the cultivator on soil properties (e.g. significant higher aggregate stability compared to ploughing) became less significant. The two-layer plough used in Germany combines the effects of turning and mixing the soil in the upper plough depth, while loosening the soil in the deeper plough layer, resulting in a good soil structure. The differences between the tillage systems in the parameters measured became less when they were releated to the winter rye. This fact was due to the lack of tillage before the seeding of the crop.
In the experiment field of Athens, under minimum and zero tillage, it was found that root and shoot parameters were significantly higher than those of ploughed plots. Physical and chemical soil properties were also improved compared to those of ploughed soil. Yields were found to be significantly correlated to the root parameters and the soil properties, and this was confirmed by the significant yield increase observed under minimum tillage.
Concluding the results show that under conditions of temperate humid climate sufficient control of weed and optimized nutrient management in organic farming can only be ensured by turning and mixing the soil. Thus, a general renunciation of ploughing cannot be suggested. Under conditions of primary tillage becomes more important for the main soil properties and more Mediterranean climate and limited soil water availability, reduced profitable in the long term.