Part 1, Section 2: Soil Fertility Management
Soil Fertility Management
Keeping good records of soil test results can be very helpful for fine-tuning fertility management. To make the most of the result, collect samples regularly and consistently (e.g., same time of year, same depth). Once you have obtained optimum to high soil test levels, the goal is to maintain those levels.
Figure 1.2-6, part A, illustrates how records of soil tests can be used to monitor soil fertility levels, fine-tune recommendations to maintain optimum levels, and evaluate odd values. A decrease or increase in a soil test level at a relatively constant yield might indicate underfertilization or overfertilization, respectively. Adjust soil test recommendations according to the observed trends. Soil test levels will vary from one test to the next; however, if an obviously odd value is observed, the soil testing lab can recheck the results and/or test a new sample for confirmation.
In a crop rotation, the objective is the same: to maintain the soil test levels in the optimum range over time. This is complicated, however, by the different crops in the rotation. On most farms with animals, manure is applied to the corn crop and not to the hay crop. This results in a buildup of nutrients during the corn part of the rotation that can be used by the hay crop later. In this type of system, illustrated in Figure 1.2-6, part B, the test levels fluctuate during the rotation, but the average trend over time remains in the optimum range. If manure is applied to all crops in the rotation, especially at N based rates, then there will most likely be a continuous upward trend in soil test P and K levels over time.
For questions about interpreting the recommendations on your soil test, contact the Penn State Extension office in your county. For questions about the analysis of the samples, contact the Agricultural Analytical Services Laboratory at University Park (phone 814-863-0841; e-mail firstname.lastname@example.org). You can also visit their Web site at www.aasl.psu.edu.