Effect of nitrogen rate and stubble catch crops on concentration of macroelements in spring wheat grain

The aim of this study was to determine the effect of different rates of nitrogen ferti- lizer and stubble catch crops on the content of nitrogen, phosphorus, potassium and ma- gnesium in the grain of spring wheat. Field experiment was carried out in 2005-2008 at Moche3ek near Bydgoszcz (53° 13' N, 17° 51' E) on the Alfisols soil classified as a very good rye complex and IIIb quality class. Nitrogen fertilization was applied at the rates of (kg N ha ?1 year ?1 ): 0; 40 (before sowing), 80 (40 kg before sowing and 40 kg in BBCH 31-32 stage), 120 (60 kg before sowing and 60 kg in the BBCH 31 ? 32 stage) and 160 (60 kg before sowing and 60 kg in BBCH 31-32 stage and 40 kg in BBCH 45-47 stage). Stubble catch crops (field pea and oilseed radish) were sown in the period from 3 to 11 of August in 2005 to 2007. After 70-77 days of plant growing, the whole biomass was plowed in as green manure. Spring wheat cv. Tybalt was sown following the catch crop,between March 30 to April 11 in 2006 to 2008. Nitrogen fertilization affected the concentrations of N, P and Mg in grain of spring wheat. Every 40 kg increment of nitrogen fertilization per ha resulted in a significant increase in the N content in wheat grain. The concentration of Mg in spring wheat grain was significantly higher when nitrogen fertilization was dosed at 120 or 160 kg per ha than at lower doses. The phosphorus content in grain of wheat grown after field pea catch crop was not related to nitrogen fertilization rates, while after the radish and in the control (without catch crop), it was significantly higher at 120 and 160 kg N per ha than at 40 kg N per ha. No effect of nitrogen fertilization on the K concentration in grain of spring wheat was found. Mean values from the three years of the N and Mg content in the grain of spring wheat were significantly influenced by the stubble catch crops. The effect of this factor on the content of macroelements in spring wheat grain was detected only in 2008, which had very low rainfalls during the growth of plants. Under these conditions, the stubble catch crops caused an increase in the content of N and a decrease of P and Mg in grain.