Effect of soil deep ploughing on winter wheat depending on soil conditions

Soil deep ploughing has a significant role on packing prevention technologies of soil layer beneath topsoil. It demands high energy consumption. This investigation was intended to clarify the effectiveness of deep ploughing in various field relief conditions. The experiments were arranged in LUA RFS Vecauce Ltd during the years 2001 - 2007. Field trials were settled in loamy sand sod-podzolic soils with equalized micro-relief during the years 2001-2004. Winter wheat was grown after clover - timothy mixture. The field was treated with glyphosate herbicide after harvesting of fore-crop. Soil tillage included soil deep ploughing in the following treatments: untreated (without tillage), deep ploughing at 0.25, 0.35 and 0.50 m depth. Subsequent soil treatment included soil ploughing at 0.22 - 0.25 m depth and direct sowing. Field trials in production fields were carried out in the years 2004-2007. Soil tillage included soil deep ploughing at the depth of 0.35 and 0.50 m. All observations were carried out in certain field points detected by GPS. The chosen fields had wavy meso-relief. Grain yield was determined by CLASS LEXION 420 GPS-established harvest maps. Soil deep ploughing at the depth of 0.50 m gave the winter wheat yield increase by 7.3% or 0.4 t haE-1 on average of three year field trials in 2001-2004. A significant positive effect of soil deep ploughing at the depth of 0.35 and 0.50 m on yield of winter wheat in the next year was determined. The impact on soil resistance from soil deep ploughing was significant only on the trail of tine and 0.10 m away from it. Significant increase of soil resistance was determined at the depth of 0.30 to 0.50 m in treatments with soil ploughing what showed formation of plough pan, but that was determined only in treatments without soil deep ploughing. Lower soil resistance in the subsoil layer was detected in production fields in the years 2004-2007 but only in treatments with soil deep ploughing in the depth of 0.50 and 0.35 m. Soil had higher moisture content in subsoil at the depth of 0.20-0.25 m if soil deep ploughing at the depth of 0.50 m was done. A significant effect of relative height of specific site, thickness of A horizon and content of organic matter on soil moisture in topsoil and also below topsoil was determined in treatments with and without soil deep ploughing. Soil moisture had an effect on soil resistance in all soil layers up to 0.50 m in both deep ploughed and non-ploughed treatments. Analysis of yield maps from the trial years 2004-2007 did not confirm a positive effect of soil deep ploughing on the winter wheat grain yield in the first year after soil deep ploughing, but if the next year characterised with increased amount of precipitations, soil deep ploughing resulted in a significant decrease of the winter wheat grain yield. The recommendations, which are designed for soil deep ploughing in levelled field conditions, do not give a positive effect in production conditions in areas with marked differences in relative height.