Efficient Nitrogen Fertilization in Grass Seed Crops with Regard to Soil Mineral Nitrogen Content and Analyzing Grass Tillers in Spring

When applying the Nmln method in grass seed crops analogously lo that in cereal crops we proceed from the experience that for a mean level of mineralisation, the sum total of soil-borne Nm1n available to plants at the beginning of the growth period and Nd Input in the form of fertiliser will provide sufficient N to the crop. The total quantity of mineral soil-borne N and fertiliser N is considered as the nominal value. The required N input can be derived from the difference between nominal value and mineral soil-borne N (Nd = nominal value• Nrnin>· For Dactylis glomerata a nominal value of 120-140 kg Nmln (0-300 mm layer of soil) was calculated after IO-year field trials on N fertilisation. Whether a second application is advisable in spring at Feekes 6 should be decided on the basis of plant analyses of the N content. Up to 3.25% N in the dry matter of Dacty/is glomerata responded to a second N rate by yield increases of more than 5%. When the N <;ontent is 3. 75% and more, yield will no longer increase.