Abstract:
The rain-fed traditional represent a big share of area cultivated in the Sudan and characterized by a very complicated situation leads to numbers of problems in agricultural statistics, in respect to area enumeration and yield estimation and poses serious threats to quality and reliability of area and production estimates. Due to these problems it is essential to pay more attention to this important sector.
The study was carried out to study the effect of plot sizes on the three different types of soils (sandy, loam and clay soils) on the estimation of sorghum yield in the traditional rain-fed sector. The estimation was obtained by using crop-cutting technique and multi-stage stratified sampling. The primary data obtained from different plot sizes namely 5x5m, 6x7m and 10x10m on each type of soil. Equal sample size allocation was used. The village was considered as primary sampling unit and the field as secondary sampling unit and the plot as third sampling unit. Sample size of twenty for each plot size and on each soil type was used, with the following hypothesis;
1-There is a direct relationship between plant density and plot size.
2-The margin of error reflects the required sample size and there is a direct correlation between the level of accuracy required and the cost of conducting survey.
3-Increase of plot size has no effect on either the precision or the accuracy.
Analysis of variance table was used to analyze the effect of sample sizes on the estimation of sorghum yield in traditional rain-fed sector. The coefficient of variation was used to identify the best stable crop yield according to the plot size. The multiple comparison method was used to detect the significant differences between means in each soil type according to the plot size by using statistical package SPSS.
The results shows and according to the conclusions of the study the plot size had not shown any effect on the yield in the different types of soils, but there was slight effect of plots size in case of plants density estimation. There seem other factors affecting the level of yields. These
iv
factors should be planting spaces, seed rate, adequate re-sowing, thinning and optimum sowing dates.
Two recommendations were recommended:
1- If the main objective of the survey is to estimate the crop yield, then the small size plots are better and recommended to use in all types of soils to save time and to save resources.
2- If the objective of the survey is to estimate the plant density then the medium plots size are better in estimation and recommended to be used.
