Reed canarygrass (Phalaris arundinacea L.) genotypes contain varying amounts of indole alkaloids which are negatively associated with grass palatability to ruminants and which are potentially toxic to animals. Forage researchers need knowledge of the influence of environmental factors such as soil fertility on alkaloid concentration to aid control of these anti-quality components of reed canarygrass.
We conducted seven experiments to determine whether the alkaloids of reed canarygrass could be modified byinherent soil fertility or by application of nutrient elements to fertile and infertile soils.
Mean alkaloid concentrations in four clones of reed canarygrass were doubled by growing the clones in an infertile peat, compared to a fertile mineral soil. Supplying the deficient nutrients (especially P and K) to an infertile peat significantly reduced alkaloids of grass growing in the soil, provided N levels did not exceed 240 kg/ha.
Ammonium sources of N (NH4Cl and urea) caused greater alkaloid concentrations in reed canarygrass than did a nitrate source (NaNO3), while grass supplied with both sources (NH,NO3) had an intermediate alkaloid concentration.
Relatively low levels of N (as low as 60 kg N/ha) applied to fertile mineral or peat soils caused increased alkaloids in grass clones inherently high in alkaloids. However, over 240 kg N/ha were required to significantly elevate alkaloid concentration in reed canarygrass growing in an infertile peat, and up to 225 kg N/ha in solution culture did not affect alkaloid concentration in a low-alkaloid clone.
We concluded that N fertilization is likely to increase alkaloid problems of reed canarygrass in situations where alkaloids are already high, but that practical levels of N (up to at least 200 kg/ha) will probably not increase alkaloid concentrations of those strains inherently low in alkaloids. Fertilization of infertile soils with deficient nutrients (other than N) may cause reduction in alkaloid concentration of reed canarygrass, even though P, Mn, or Cu individually did not affect alkaloids.
None of the fertilizer elements changed the type of alkaloids (gramine, DMT, or 5-MeO-DMT) of the various clones and seed sources used in the seven experiments, indicating that this variable was genetically controlled.