Determining of sample size in order to annual yield estimation in the steppic rangeland of Yazd province

Investigation for adequate sample size is essential for annual yield measurement in each range sites. For this purpose, a key area was selected in the Nir range research station that is indicator of steppic rangelands of Yazd province. One hundred and fifty 2m-1 quadrate plots with 25 m space were systematically located on 5 transects. Forage yield measurements were carried out with clipping and weighting methods in mid-May 2004. Forage yield per hectare were calculated based on 10 until 150 mentioned plots data. Adequate sample size was determined with drawing method. Results showed that total forage yield in the area were assessable with clipping and weighting method by thirty 2m-1 quadrate plots, but separate species yields were analyzed by one hundred 2m-1 quadrate plots data. Forage yield estimation with clipping and weighting in thus sample size is more consumed time and expensive. Thus, the double sampling model with cover were recommended for these rangeland inventory that were measured cover and yield with 100 and 25 plots, respectively.