Auteur: Rietberg P., De Wit J. and Van Eekeren N.
Jaar van uitgifte: 2015
Inclusion of red clover (Trifolium pratense) in grasslands offers important economic and environmental advantages as nitrogen (N) fertilizer is replaced with N from N2 fixation. These advantages seemed to be reduced under high fertilization rates. In a field experiment we compared perennial ryegrass swards (Lolium perenne) with grass-clover mixtures in which the artificial N fertilizer was omitted. The experiment was conducted at two locations (sandy and clay soil) at high fertilization levels (254 and 306 kg total-N ha‑1 on grass-clover and 389 and 489 kg total-N ha‑1 on the pure grass swards). Grassclover mixtures produced more dry matter (+18%), digestible energy (+12%), crude protein (+45%) and digestible protein (+27%). Economic evaluation at farm level shows that grass-clover mixtures had a surplus of €510 ha‑1 year‑1 over pure grass swards. This surplus would be reduced (to €282 ha‑1) if the higher crude protein content of grass-clover cannot be balanced in the feed ration, resulting in extra N excretion of the animals and subsequent higher costs for manure disposal if maximum allowable manure application rates per ha are exceeded. These results show that inclusion of red clover in grasslands has agro-economic benefits, also under high fertilization rates.