*2.1. Experiments Set Up*

Three series of field experiments with winter oilseed rape (*Brassica napus* L.) were conducted during the 2008/09, 2009/10, and 2010/11 seasons. Each year, two different fields (sites) were investigated. Field experiments were conducted on soils with texture ranging from sand/sandy loam to sandy clay loam, classified as Albic Luvisol. The content of the available nutrients (measured each year just after a fore-crop harvesting from two soil depths of 0.0–0.3, and 0.3–0.6 m) ranged, depending on the nutrient, from low to very high, and it was, in general, sufficiently high for covering the nutrient requirements of the high-yielding WOSR (Table 1).




(soil/solution ratio 1:5; m/v); 6 Soil layers: 0.0–0.3/0.3–0.6 m; 7 Soil agronomy class; 8 classes of available nutrient content: L—low, M—medium, H—high, VH—very high.

The local climate, classified as intermediate between Atlantic and Continental, is seasonally variable (Table 2). Precipitation during the period extending from January to July was for most of the sites slightly higher than the long-term average, which amounted to 347.5 mm. Each year, the highest amount of precipitation was recorded in July. In 2010, a severe shortage of precipitation was recorded in June, a critical month with respect to pods and seed growth [14], but it was preceded by high precipitation in May. Air temperatures were, with the exception of Wieszczyczyn in 2010, around the long-term average.
