Specific genotypes of plantain (Plantago lanceolata) vary in their impact on sheep urine volume and nitrification in the urine patch

Abstract

Plantain has the potential to reduce nitrate leaching through a number of mechanisms. In an indoor study, sheep were offered either perennial ryegrass or different plantain genotypes while aiming to achieve similar dry matter and water intakes. Supplementary water was sprayed on the feed to achieve the latter objective. Animals fed two cultivars (‘Tonic’ and ‘Agritonic’, marketed as “Ecotains” with claims around the potential to reduce nitrate leaching, and breeding lines (from a breeding program aimed at improving aspects of leaching mitigation) produced significantly more urine (4925 and 4887 ml/day, respectively) than those fed a range of commercial plantain cultivars (averaging 4333 ml/day) or perennial ryegrass (3993 ml/day). These results suggest the plantains marketed as “Ecotains” and those in the environmental breeding program may have diuretic effects on sheep, thereby reducing the concentration of nitrogen in the urine. In a soil incubation experiment, urine from sheep grazing either perennial ryegrass or ‘Agritonic’ plantain was applied to soil microcosms (70 ml vials containing 20 g of soil). Urine from sheep grazing the plantain, showed a slower overall nitrification rate (especially in the first 28 days post-application) when a significantly lower proportion of the urinary N was converted to nitrate. Both these observations support the use of specific genotypes of plantain to assist in reducing nitrate leaching.