The European Perspective On Understanding Yield Variation.

This paper will discuss precision farming from the European perspective.

In a number of field studies a correlation analysis, principal component analysis and clustering were tested for the relation between soil and yield variability, in the frame of the development of precision agriculture management.

A static approach looked at soil data and yield data. Three principal components for soils describe the overall soil texture variation over the field, soil organic matter, soil nitrogen in early spring and acidity and phosphate variability. Correlations between yield and crop measurements and soil principal components did lead to zones that could be used to set up management zones. The average soil properties of these zones could be used as a start to determine causes of variability in crop growth and yield, using a broader knowledge on the soil-plant interaction.

It was also found that there exist zones with different yield potential due to previous soil erosion. High grain yield, straw yield and biomass could be related to flat, high places in the field with little erosion. Good grain yield, low straw yield and high harvest index were found on relatively steep slopes subjected to erosion. High straw yield and low grain yield were found at low places in the field on relatively steep slopes. Lowest grain yield, straw yield and biomass were located on steepest slopes with high erosion and in depressions where accumulation of eroded soil took place and slumping and crusting of the soil were present. However these relations may change from one year to another as climatic conditions are different.

Furthermore, it turned out that the field history (previous crops, the associated use of fertilizers and herbicides or other treatments) and farmer’s knowledge were very important to explain some of the observed variability in yields resulting in financial profits or losses in different areas of the fields.

Crop response to treatments is another approach for precision farming. Since crop production is a process that varies in time as well as in space, it is considered that crop observations and measurements during the growing season can help to manage the final yields. This is especially so in case of split fertilizer application. Optical instruments were used to see how they can give an indication of crop cover and crop response to treatments and would be helpful in crop management. At mid-season, the applied nitrogen to the crop was the factor that determined change in crop cover percentage. This in turn had good correlations with total nitrogen in the crop and protein content in grain, the yield variables that are best related to applied nitrogen. This means that observed changes in crop cover measurements during the growing season can be used to adjust nitrogen fertilization.  Of course, split application of nitrogen must be tailored according to weather conditions since water availability affects the nitrogen uptake.