Evaluation of the accuracy of systematic and random sampling methods in estimating the density of weed seedlings in corn fields under different irrigation systems

In order to investigate the effectiveness of random, zigzag and diagonal sampling methods in seven sampling levels in estimating the weed population of corn fields under drip, furrow and sprinkler irrigation systems, a research was conducted in 2020 year in six corn fields. In order to estimate the accuracy of the sampling methods, first, the studied area was gridded with the standard grid sampling method of 5 m × 5 m and at the intersection of the lines using a square quadrat an area equal to one meter. The data related to the species number and density of weed seedlings by species were recorded in one stage. The results showed that increasing the sampling levels increased the accuracy in estimating the number of weed species in different sampling methods. At low sampling levels, the random sampling method estimated weed density with less error, but with increasing sampling levels, the accuracy of diagonal and zigzag systematic sampling methods increased and with 20 and 21 sampling units, respectively, they estimated the density of seedlings of the weed population with acceptable accuracy. With the increase of sampling levels, the amount of error in estimating the density of C. album species decreased so that the lowest error was in levels IV , VI (with 24 samples in random and diagonal methods and 25 sample in zigzag method) and VII (with 28 samples in random and diagonal methods and 29 samples in zigzag method) were observed with 0.04, 0.02 and -0.06 respectively.