The "microplot" fertilization treatments are used in experiments 1, 2, 4, 8, 9, 11, 23, 25, and 52. Experiments 5, 6, 28, 36,53,97, 98 and 100 are conducted within plots that are fertilized and should be treated as part of the fertilized plot.  There are nine treatment levels, assigned a letter A through I. This is also equivalent to the numeric labels 1 to 9. Treatment levels A through H differ in the amount of NH₄NO₃ added. Treatment I is a true control and receives no nutrients. The nutrients are applied twice a year, once in early May and once in late June. An exception is experiment 25 where time of application is experimentally manipulated. Not all experiments  use all possible treatments. Nutrients are given in g/m² for each fertilization; plot area and treatments used follow the nutrient lists.

Treatment A to H receive the following base nutrients:

The description for making trace mineral sand is at the end of this section.

The amount of NH₄NO₃ fertilizer added at the different treatment levels is:

These rates are added twice a year. Actual annual N addition is calculated as:

0.34%N * rate (g/m²) * 2 times/year

The trace mineral stock solutions are made by adding the following grams of reagent to 1000 ml of water:

CuSO₄*5H₂O 9.8 g
ZnSO₄*7H₂O 22.0 g
or
ZnCl₂ 10.5 g
CoCl₂*6H₂O 10.0 g
MnCl₂*4H₂O 180.0 g
Na₂MoO₄*2H₂O 6.3 g
H₃BO₃ 6.0 g

The trace metal solution is made by combining 120ml of each stock solution, adding 67.2g of citric acid dissolved in deionized water and adding deionized water to bring the volume to a total of 2 liters. The working solution is then autoclaved to chelate the trace metals.

The size of the plots and treatments used for each experiment are:

Some changes and/or additions occur from year to year for some experiments. These changes are listed below. Unless specific experiments are mentioned, these differences apply to all experiments in a category.

In 1982, 30ml of each stock solution was combined with 16.8g citric acid, brought to a total volume of 1 liter, and autoclaved to dissolve. 1.5ml of this solution was added to 30ml of silica sand, mixed and dried.

In 1983, 60ml of each stock solution was combined with 25g of EDTA brought to 1 liter, and autoclaved to dissolve. 1ml of this solution was added to 10ml of sand and added to each plot.

In 1984, 60ml of each stock solution was combined with 25g of citric acid and brought to 1 liter.

In 1985, the first fertilization for experiments 1 and 2,
Treatment F received an extra 23 g/m² of CaCO₃
Treatment G received an extra 118.5 g/m² of CaCO₃
Treatment H received an extra 132.5 g/m² of CaCO₃

In 1985, between fertilizations for experiments 1 and 2,
Treatment G received 137.5 g/m² of CaCO₃
Treatment H received 206.25 g/m² of CaCO₃

In 1985, the second fertilization for experiments 1 and 2,
Treatment F received an extra 23.0 g/m² of CaCO₃
Treatment G received an extra 252.7 g/m² of CaCO₃
Treatment H received an extra 441.1 g/m² of CaCO₃

In 1985, the first fertilization for experiment 4,
Treatment E received no CaCO₃
Treatment G received an extra 45.5 g/m² of CaCO₃

In 1985, both fertilizations for experiments 8, 9, and 11,
Treatment F received an extra 23 g/m² of CaCO₃
Treatment G received an extra 43.5 g/m² of CaCO₃
Treatment H received an extra 57.5 g/m² of CaCO₃

In 1989, lime was added to adjust pH to the following treatments in the spring:

Quantities of lime stone (g/plot):

In the fall of 1989, each plot receiving treatments B, C, D, E, F, G and H in field D of experiment 1, received 1067g of lime to adjust pH.