Species, climate and fertilizer effects on grass fibre and protein in tropical environments

SUMMARYA 3-year experiment (2005–07) was conducted on Reunion Island (France) to evaluate the effect of species, climate and fertilization levels on fibre and protein fractions of tropical (C4;Chloris gayanaandPennisetum clandestinum) and temperate (C3;Dactylis glomerataandLotium multiflorum) grasses. A near infrared reflectance spectroscopy (NIRS) prediction referential was developed to estimate neutral detergent fibre (NDF), acid detergent fibre (ADF), crude protein (CP), NDF insoluble protein (NDF-IP) and ADF insoluble protein (ADF-IP). The NIRS equations were then used to screen many regrowth grass samples collected at heading stage continuously for 3 years to evaluate their changes during the seasons. Results showed that grass species differed significantly in fibre and protein fractions. NDF, ADF and ADF-IP were the lowest inD. glomerata/L. multiflorumand the highest inC. gayana. The wet season was associated with higher NDF, ADF and NDF-IP inD. glomerata/L. multiflorumand lower NDF-IP inP. clandestinum.Fertilization increased the CP inC. gayanaand the NDF-IP inP. clandestinum, but decreased the ADF-IP of bothC. gayanaandD. glomerata/L. multiflorum. Growth rate strongly changed NDF, ADF, NDF-IP and ADF-IP although no change in CP appeared. In general, NDF, ADF and NDF-IP increased with the growth rate. In contrast, the ADF-IP content decreased from slow to fast growth rate inC. gayanaandD. glomerata/L. multiflorum. Growth rate changes were thus considered as a general indicator for fibre and protein fraction variations of these grasses.