Herbage mineral nutrition indexed as tools for rapid mineral status diagnosis in tropical pastures

Abstract

The animal production sector in the tropics is increasingly becoming challenged with the limited availability of pastures. There is need therefore to explore other options to suppliment the available pastures. The objectives of this study therefore was to understand how herbage mineral dilution indices used in developed countries as tools for controlled fertilisation, could be adapted in a tropical environment where high seasonal variations with regard to availability occur in pastures. A 3-year study was carried out in La Réunion Island, Indian Ocean. Forty
nine farms, with swards made of either temperate or tropical grasses, grazed or mowed, were visited between four and five times a year. Dry biomass and dry matter contents were reported at each sample collection; whereas mineral indices were calculated from chemical analysis with a view to generate relevant fertilisation recommendations.
Although the dry matter ( DM) values of less than 20% indicated a better stage of exploitation for the grasses, the data consistently indicate a decrease in the seasonal differences of dry biomass for grazed species. The use of indices, which combine both plant mineral status and pasture biomass, appeared relevant indicators for farmers and for pasture experts in tropical countries, and can be predicted through near infrared spectroscopy with an acceptable precision (R2 = 0.80, 0.60 and 0.91, for nitrogen , phosphorous and potassium, respectively). With reduced cost of pasture feed analysis using the NIRS, farmers can be able to make informed decisions based
on scientific data. Fertilisation is one of the potential options to improve pasture management as indicated by findings of this study. This is useful evidence-based information that could be incorporated in extension packages and resource materials for dissemination and subsequent adoption by livestock farming communities to improve produtivity.