Field prediction of alfalfa (Medicago sativa L.) fibre constituents in northern Europe

Models to predict neutral detergent fibre ( NDF ) and acid detergent fibre ( ADF ) of alfalfa before harvest have been developed in the USA , but have not been tested in northern Europe or above 50°N latitude. Our objective was to test predictive equations for alfalfa quality ( PEAQ ) and the New York prediction equation for alfalfa quality ( NYPQ ) for estimating alfalfa NDF and ADF in northern Poland. A total of 275 alfalfa samples, varying in height and maturity, were collected from twenty farm fields over 3 years. Observed NDF and ADF values were regressed on predicted values. The accuracy of PEAQ for predicting NDF and ADF in Poland was equal to that observed in the USA ( r 2 > 0·89; RMSE < 21·6). In most cases regression equations were not biased (slope = 1 and y‐intercept = 0), and when there was bias it was minimal. The relationship between observed and NYPQ prediction of NDF was also strong ( r 2 > 0·88; RMSE < 23·0), but these equations were extremely biased. The results demonstrate that the PEAQ model provides a simple, rapid and reasonably accurate means to estimate fibre concentrations of alfalfa before harvest, appropriate for the growing conditions of northern Europe.