Yield and chemical composition responses of Lablab purpureus to nitrogen, phosphorus and potassium fertilisers

An experiment was conducted over 2 years to investigate the response of Lablab purpureus plants and shed leaves to nitrogen, phosphorus and potassium fertilisers, applied alone or in combinations. No responses in plant DM yield were seen in the first year to any fertiliser combination. Applying both nitrogen and phosphorus fertilisers increased the yield of shed leaves. but adding potassium negated any advantage and also reduced plant modified acid-detergent (MAD) fibre levels. In Year 2. no response to any fertiliser was obtained. Sodium concentrations in both harvested plants and shed leaves were considerably below the requirements for ruminant growth or lactation, but tended to be increased by N + P + K fertiliser. In both years, the crude protein and phosphorus levels in shed leaves were increased by most fertiliser treatments that contained phosphorus. It is concluded that, as consistent benefits in DM yield or plant composition were not observed, the application of N, P and K fertilisers cannot be recommended in these circumstances.