Nitrification inhibition by urine from cattle consuming Plantago lanceolata
Plantain (Plantago lanceolata L.) has the potential to indirectly reduce nitrate leaching from urine patches via compounds excreted in the urine of animals grazing the forb acting as biological nitrification inhibitors. Proof-of-concept research was previously undertaken using sheep urine, but it is important to examine whether this effect also occurs with cattle urine since cattle pose a greater N-leaching risk due to their higher urinary-N load. Housed dairy heifers (n=4) were assigned ad libitum dietary treatments of perennial ryegrass/ white clover or plantain for 14 days. On day 14, urine was collected through a sterile Foley catheter into a sealed container. Cattle then switched dietary treatment and urine was collected after a further 14 days. Urine samples were applied to soil microcosms and the net nitrification rate during a 35-day incubation determined. Similar urine-N concentrations were applied initially but a slower rate of soil nitrification was observed in the microcosms treated with urine from plantain-fed cows compared with those treated with urine from ryegrass/white clover-fed cows. The urine samples collected after the crossover showed a wider treatment difference in total N concentration, but also demonstrated a reduction in soil nitrification rate under the plantain urine. These results show similar trends to those previously reported for sheep urine.
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