Intra-field yield variation over crops and years

ata and yield maps were obtained from farmers using their own combine harvester equipped with commercial systems for yield easurements and satellite positioning. Three quarters of the datasets collected were abandoned due to being incomplete or roblems occurring when overlaying maps from different years. Intra-field yield variation was investigated in the remaining 82 ields. Some fields had data present for 4 years. The predominant crops were winter wheat and winter barley. The coefficient f variation (cv) ranged from 0.05 to 0.22, which was comparable to the residual cv usually found in agricultural experiments. n spring and winter rape the average cv was 0.15, cereals varied from 0.05 to 0.22. The distribution of yields within fields as generally non-normal; it was negatively skewed (left tailed) and broader than a normal distribution. Although the highest ielding crops and fields had the lowest intra-field variation, the distributions of yield were mostly negatively skewed. egression analyses of intra-field yield pattern between years gave R2 values from 0 to 0.81, with an average of 0.27. Similar rops and crops with small average yield differences gave the highest R2 values, even when they were separated by more than ne year in time. Prediction of intra-field variation, trend maps of temporal stability, and maps of classified management, could herefore be improved by developing them for individual crops based on the most appropriate previous crops. It appears nlikely that trend maps will account for much more than 1/3 of the annual intra-field variation on average. The possibilities for eveloping maps of classified management based on similar quality yield maps as obtained from farmers in the present nvestigation, appears limited because of the high frequency of erroneous data sets, systematic errors in the recorded data and heir restricted yield predictive ability.