Comparison the effectiveness of grid sampling methods and quadrate shape in estimating the spatial distribution of weed populations in corn fields under different irrigation systems

In order to investigate the effectiveness of grid methods in estimating the spatial distribution of weed populations in corn fields under drip, furrow and sprinkler irrigation systems, a research was conducted in 2020 year in three corn fields. The fields were gridded with two methods of 5 m × 5 m and 5 m × 10 m. At the intersection of the lines, using square (100×100 cm) and rectangular (80×125 cm) squares perpendicular to the planting lines, data on the density and diversity of weed seedlings were recorded by species. In general, the spatial distribution maps confirmed the distribution of weed patches and the effect of the irrigation system on the appearance of patches, which was affected by the biological characteristics and wetting pattern of the field soil. The variogram of the studied species showed that in the furrow irrigation system, the range of influence of the species increased compared to other irrigation systems, The distribution range of the studied species was smaller in the drip irrigation system. The output maps showed a higher number of dense patches of weed species in the sprinkler irrigation system, possibly due to the uniform wetting pattern of the field. Sampling methods of the studied species showed differences in the estimation of spatial distribution maps. The rectangular grid sampling method of 5 m × 10 m mainly showed the size of the weed patches to be slightly larger than the square grid method of 5 m × 5 m,