- Author: Mark Bolda
Nice, very short article - doesn't take more than 5 minutes to read - addressing the general question of soil acidity and nutrient availability for plants. As many of you know, I am a big fan of soil acidity for plant culture but as the article clarifies, acidity is only beneficial down to a point, below which the availability of N, P, Ca, Mg and K drops off too much apparently.
Key here is that favorable pH for plants is in a RANGE from 5.9 to 7.0. Still, if you peruse the included graph closely you get the strong sense that optimum availability of most nutrients is at 5.9, especially the micronutrients iron, copper, manganese and zinc.
Many of our soils for berries in Salinas and Watsonville range from 6.5 to 7.5, so there are many above optimum (for many reasons, I know that). It would be an interesting avenue of research to pursue a soil that is at 5.9 and see how well a crop of berries does there.
- Author: Mark Bolda
Below is a look at what happens to a soil following application of mustard seed meal (MSM) at 1.5 T per acre and mustard seed meal (again 1.5 T per acre) + crab meal (500# per acre) as separate treatments two weeks after fumigation with Ally 33 (67% AITC, 33% chloropicrin applied at 340# per acre on Oct 7).
Grower standard was methyl bromide/chloropicrin applied at 350# per acre. Planting took place Nov 3.
A soil sample taken on Nov 7 did not show differences in soil aspects analyzed between any of the treatments, although ammonium - N concentrations were surprisingly high (30 ppm and up) and nitrate - N numbers tended to be quite low (6 ppm and below).
Remarkably, look what has happened in the 4 weeks since that sample. Bear in mind that the grower has since sprinkled overhead several times and we had a good amount of rain as well. Commenting continues below the tables.
Unless otherwise indicated, units are in ppm of dry soil.
Table 1A. Soil analysis from December 7, 2016
|
Sample |
pH |
EC (dS/m) |
Nitrate – N |
Ammonium – N |
|
Methyl bromide grower standard |
7.4 |
0.9 |
11.3 |
4.7 |
|
Mustard Seed Meal |
7.1 |
1.7* |
34* |
20* |
|
Mustard Seed Meal + Crab Meal |
7* |
1.8* |
32* |
12* |
*Student's T-Test; different from grower standard at 5% level of significance.
Table 1B. Soil analysis from December 7, 2016
|
Sample |
(P) |
(K) |
(Ca) |
(SO4) |
(Mg) |
(Mn) |
Fe |
Na in meq/L |
Cl in meq/L |
|
Methyl bromide grower standard |
51 |
148 |
3100 |
278 |
178 |
8.9 |
18 |
1.9 |
3.2 |
|
Mustard Seed Meal |
54 |
190* |
2933 |
318 |
193 |
19.2* |
16 |
1.5 |
1.9 |
|
Mustard Seed Meal + Crab Meal |
60 |
185* |
3100 |
589 |
150 |
20.1* |
16 |
1.5 |
1.9 |
*Student's T-Test, different from grower standard at 5% level of significance.
One sees immediately that the pH has fallen, even significantly, in plots treated with mustard seed meal and mustard seed meal + crab meal. This is not surprising, since in the month's time since the initial sample on Nov 7, the ammonium has clearly nitrified (releasing 2 H+ ions per molecule, in turn acidifying the soil) creating a big pool of nitrates which have gone up significantly over the grower standard.
EC has gone up a bit due to the higher nitrates (NOT because of sodium or chloride), and interestingly levels of manganese (Mn) a mineral sensitive to acidification apparently, have soared in both MSM treated plots. Levels of available potassium (K) have gone up significantly also in MSM treated plots.
Quite interesting on the whole. By the way, a soil report like this makes for pretty good reading, and outside of the EC which is for the time being a little high in the MSM plots, all the other numbers are right where I like to see them.
Stay tuned on this one; we are following all of this trial through the season.
