Spatial and temporal variability of wheat grain yield and quality in a Mediterranean environment: A multivariate geostatistical approach

In Mediterranean countries, on top of the erratic weather pattern, rainfed wheat grain yield and protein content in a field are spatially variable due to inherent variability of soil properties and position in the landscape. The objectives of this three-year field study were: (i) to assess the spatial and temporal variability of attributes related to the yield and quality of durum wheat production; and, (ii) to examine the temporal stability of sub-field management classes derived from (i). A Geostatistical approach was used to analyze data collected in each year from 100 georeferenced locations. In particular, block-kriging was used to produce maps of gluten and protein content, test weight, biomass weight and Harvest Index. The multivariate spatial data sets were then analyzed by Factorial co-Kriging Analysis (FKA). The classes obtained from the FKA output were compared with the yield maps in order to assess their production potential. The first factors relating to each year were also compared by using contingency matrices, to estimate the temporal consistency of field delineation. In the first two seasons, at most, about 50% of the total spatial variance of the crop attributes was ascribed to production potential. In the third season the variation was more erratic, equally influenced by all variables. The contingency matrices have showed that only 26% on average of the spatial variation of the attributes of wheat production was characterized by temporal stability. The present study highlighted the influence of climatic conditions over the persistence of wheat crop responses.