Agronomy Degree Practice Exam

How many soil cores are recommended to obtain an adequate soil sample from each management zone in a 160-acre field?

1. 5-7 cores

2. 20-40 cores

3. 1-5 cores

4. 15-20 cores

The correct answer is: 15-20 cores

To obtain an adequate soil sample from each management zone in a 160-acre field, the recommendation is to collect 15-20 soil cores. The reasoning behind this number is that a greater quantity of cores provides a more reliable average representation of the soil properties within the management zone. This is essential for accurate nutrient testing, pH measurement, and other essential soil characteristics, which can vary significantly across a field due to factors like topography, drainage, and previous land use. Sampling 15-20 cores allows for better homogenization of the sample and reduces the likelihood of anomalies skewing the results. If fewer cores were taken, such as just 1-5 or even 5-7, the sample may not capture the variability often present in soil properties, leading to less accurate assessments and potentially poor agricultural decision-making. Collecting 20-40 cores may seem excessive for simpler or more uniform zones, but when dealing with diverse management zones, the recommended amount ensures a thorough analysis representative of the area's conditions.