Landscape Management of Agronomic Processes for Site-specific Farming

This project is focusing on how landscape-scale variability influences soil properties and processes that are related to the soil’s release of N, P, K, and S and crop responses to both soil and fertilizer N, P, K, and S. The long-term objective of the project is to develop agronomic models, which will assist farmers in making fertilizer management decisions based on landscape units. The field test site chosen for this trial has rolling topography in the Black soil zone of east-central Alberta. The cooperating farmer has been using a combine yield monitor and global positioning system (GPS) to measure yield variability on his farm, as well as variable rate fertilizer application to compensate for in-field differences in soil residual nutrients.

Using ion exchange probes, placed in the soil at two-week intervals, the pattern of plant nutrient availability was measured throughout the growing season. The drier and more eroded shoulder position in the field showed the lowest soil P supply rates, less than that measured in the backslope (mid) and footslope (lower) positions. However, little difference was observed between the backslope and footslope positions in soil P supply rates. Soil K supply showed a progressive response decreasing from the footslope to the backslope and then the upper shoulder position. Soil K appears to be influenced by soil moisture conditions and possibly the higher historic crop residue that was produced at the footslope position. Ion exchange probes were also installed using root exclusion tubes, as a means of determining the soil P and K supply rate in the absence of crop uptake. These results were similar to those obtained from probes used in crops. The results to date indicate that the differences in nutrient dynamics reflect those soil processes controlled by temperature and moisture. Future work will evaluate the nutrient dynamics and crop growth functions of the model Ecosys. In addition, other models (EPIC and DSSAT) will be evaluated using the data from this site. AB-19