| Popis: |
The choice of agricultural land use or management can be based entirely on a soil map or on results of soil analysis or on a combination of the two. This paper presents the kind of comparison that should form the basis for choosing among these alternatives. It is illustrated with the dry matter yield of barley (Hordeum vulgare cv. Julia) in topsoil samples. The results clearly indicate the superiority of the combination of mapping and analysis over either of these for crop yield prediction. Thus, subdividing the soil of the study area of 250 ha into 2, 3 and 4 mapping units reduced the undescribed variability from 100% to 93, 73 and 66% respectively. There was no further benefit from mapping into 5 and 6 units. Regressions of yield on values of 1, 2 and 3 soil properties reduced the undescribed variability to 62, 60 and 58& respectively. There was little benefit from including more soil properties in the regression. Regressions on 2 and 3 soil properties within each of 2 mapping units reduced the undescribed variability to 50 and 48%, while for 3 units it was reduced to 45 and 34% respectively. |
