Spatial relationship between soil properties and wheat grain yield under the conditions of competition with wild barley (Hordeum spontaneum Koch.) using geostatistical method

Knowledge of spatial variation in yield as well as the factors that affect it, will improve field management. Geostatistical methods are very effective in identifying and describing the distribution patterns of soil variation in the field. In this regard, this research was conducted to study the spatial relationship of some important physical and chemical properties of soil with bread wheat cv. Pishgam grain yield under the conditions of competition with wild barley using geo-statistical method.

In 2019-2020 cropping season, a field experiment was conducted in Isfahan, Iran in the form of a grid system with a distance of 2 × 2 meters. At each grid point, soil properties, bread wheat cv. Pishgam grain yield and wild barley density were measured and recorded. Experimental variograms, model fitting, kriging estimation and drawing maps for different traits were done using GS+ software. To describe the spatial correlation between two variables, a cross-semivariogram was employed. Spearman's correlation coefficients were also calculated using SPSS software (Ver. 16).

The results showed that soil properties in the field varied from one place to another and were seen as patches with different sizes and shapes on the maps. The lowest (1.6%) and the highest (23.7%) of coefficient of variation (CV) for the studied soil properties were related to pH and nitrogen, respectively. The results indicated that the distribution of wild barley was not even or random, but had a patchy or cumulative distribution pattern. The interpolated maps by kriging showed that the weed patches generally tended towards the edges of the field. Wild barley had a strong spatial correlation with nitrogen (N) and phosphoreous (P) of the soil, while this weed was found in soils with low amount of clay and potassium (K). The cross-semivariogram showed that bread wheat cv. Pishgam grain yield had strong spatial correlation with N, K, pH, clay and silt properties of the soil with correlation coefficient of 75.0, 83.2, 83.6, 94.1 and 78.6%, respectively within the distances of 6.1, 3.7, 4.7, 14.0 and 3.2 meters. The results of cross-semivariogram, estimation of Spearman's correlation coefficients and also comparison of maps showed the negative relationship between bread wheat cv. Pishgam grain yield and wild barley density in the field. Spatial correlation between weed density and grain yield was 86.9% within the distance of 14.0 meters.

In general, the results of this research indicated that the spatial variation of soil properties and also weed density caused patchy patterns of bread wheat cv. Pishgam grain yield in the field. Knowledge of the spatial distribution of soil nutrients and weeds density in the field can be useful for site specific management of the breat wheat crop.