دانلود رایگان مقاله انگلیسی روابط فضایی بین عملکرد غلات و خاصیت فیزیکی خاک انتخاب شده و ساختار شیمیایی - الزویر 2018

abstract

Sandy soils occupy large area in Poland (about 50%) and in the world. This study aimed at determining spatial relationships of cereal yields and the selected soil physical and chemical properties in three study years (2001 −2003) on low productive sandy Podzol soil (Podlasie, Poland). The yields and soil properties in plough and subsoil layers were determined at 72–150 points. The test crops were: wheat, wheat and barley mixture and oats. To explore the spatial relationship between cereal yields and each soil property spatial statistics was used. The best fitting models were adjusted to empirical semivariance and cross-semivariance, which were used to draw maps using kriging. Majority of the soil properties and crop yields exhibited low and medium variability (coefficient of variation 5–70%). The effective ranges of the spatial dependence (the distance at which data are autocorrelated) for yields and all soil properties were 24.3–58.5 m and 10.5–373 m, respectively. Nugget to sill ratios showed that crop yields and soil properties were strongly spatially dependent except bulk density. Majority of the pairs in cross-semivariograms exhibited strong spatial interdependence. The ranges of the spatial dependence varied in plough layer between 54.6 m for yield × pH up to 2433 m for yield × silt content. Corresponding ranges in subsoil were 24.8 m for crop yield × clay content in 2003 and 1404 m for yield × bulk density. Kriging maps allowed separating sub-field area with the lowest yield and soil cation exchange capacity, organic carbon content and pH. This area had lighter color on the aerial photograph due to high content of the sand and low content of soil organic carbon. The results will help farmers at identifying sub-field areas for applying localized management practices to improve these soil properties and further spatial studies in larger scale.

5. Conclusions

The application of the geostatistical approach including basic statistics, direct semivariograms, and cross-semivariograms improved the description of the spatial dependence between cereal yields and selected soil properties on a field scale. The cross-semivariograms and the kriging maps allowed delineating a field area with a low cereal yield and soil CEC, SOC, and pH. The reduced cereal yield in the distinct area was noted consistently in each of the three study years with different weather conditions. The distinct area is characterized by higher sand content and lower silt content, compared to other part of the field. This area in the experimental field along with some neighboring areas is seen on the aerial photographs as one similar zone separated by lighter soil color, probably due to the greater content of sand and the lower content of SOC. This implies that the analysis of the kriging maps together with a larger-scale aerial photographs allows delineating a larger critical zone based on the data of soil textural composition and organic carbon content that are often available in soil databases. In connection with this observation, further more detailed studies on the spatial relationships between crop yields and soil properties and on their usefulness in upscaling were undertaken on a larger scale.