SAMPLE OPTIMIZATION FOR 5 PLANT-PARASITIC NEMATODES IN AN ALFALFA FIELD

  • 1 January 1981
    • journal article
    • research article
    • Vol. 13  (3) , 304-313
Abstract
A data base representing nematode counts and soil weight from 1936 individual soil cores taken from a 7-ha alfalfa field was used to investigate sample optimization for 5 plant-parasitic nematodes: Meloidogyne arenavia, Pratylenchus minyus, Merlinius brevidens, Helicotylenchus digonicus and Paratrichodorus minor. Sample plans were evaluated by the accuracy and reliability of their estimation of the population and by the cost of collecting processing and counting the samples. Interactive FORTRAN programs were constructed to simulate 4 collecting patterns: random: division of the field into square sub-units (cells); and division of the field into rectangular sub-units (strips) running in 2 directions. Depending on the pattern, sample numbers varied from 1-25 with each sample representing 1-50 cores. Each pattern, sample and core combination was replicated 50 times. Strip stratification north/south was the most optimal sampling pattern in this field because it isolated a streak of fine-textured soil. The mathematical optimum was not found because of data range limitations. When practical economic time constraints (5 h to collect, process and count nematode samples) are placed on the optimization process, all species estimates deviate no more than 25% from the true mean. If accuracy constraints are placed on the process (no more than 15% deviation from true field mean), all species except Merlinius required < 5 h to complete the sample process.

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