Pest Control Through Soil Fertility

PROJECT BACKGROUND
Our farm has undergone many changes in the last four years. When this study began, we were focused on raising berries and vegetables, which we sold from our on farm market. We also raised free range chicken, hogs, and turkeys, which we direct marketed to our customers. In the last year things have changed quite a bit in my off farm employment. This has led us to drop our labor intensive enterprises. Currently our only farming enterprise is a small herd of meat goats, which we began raising about two years ago, and raising food for our family.

Before 2000 when this study began, we had started to use sustainable practices such as use of ground covers for weed and soil erosion control, some use of organic fertilizers, little use of chemical pesticides, use of manure from neighboring farmers, selling of produce locally, and rotation of crops.

PROJECT DESCRIPTION AND RESULTS
To determine whether or not organic fertilization increased pest resistance in tomato and bean crops by comparing an organic fertilization, conventional chemical fertilization system, and no fertilization. The crop was tomatoes the first and third years with a rotation of green beans the second year. Although we received the SARE grant for the year 2001, we actually started the project using a Missouri Demonstration Award in 2000 and extended it so that we could have a better study. The organic system we used (developed by the Christian Agriculture Stewardship Institute (CASI) claims that the soil needs a few years to balance and develop the healthy array of biological life needed to produce maximal pest resistance, so we chose to do a three year study (which turned out to be a four year study).

Process:
In the year of 2000 we started tomatoes (Celebrity) from seed in our own greenhouse. We set up test plots to compare organic fertility methods with conventional fertility methods. Some of the treatments included pesticide application; some did not. Each treatment was randomly replicated three times. Each plot was 3’x14’, containing seven tomato plants. Below is a small table describing the different treatments.

Table 1. Treatment Description
Treatment #, Fertility, Pesticide?
1, organic, no
2, conventional, no
3, none, no
4, organic, yes
5, conventional, yes
6, none, yes

We took soil samples and got fertility recommendations for organic and conventional fertility methods. The soil samples were analyzed by Midwest Laboratories Inc, in Omaha Nebraska. The organic fertility recommendations came from Carroll Montgomery, president of the Christian Agriculture Stewardship Institute and the conventional recommendations came from Gaylord Moore, Regional Horticulture Extension Specialist in Green County for the University of Missouri. The soil was prepared and the tomatoes planted in May. Pesticide applications were made on appropriate treatments, and follow up fertility steps were taken. We have not included specific fertility recommendations – these recommendations were made from the results of our soil sample results. No other farmer will get the same soil sample results we did. Each treatment was sprayed with a Bt product to control tomato hornworm. Tomatoes were staked with a stake and weave system. We harvested from late July through September. We did not harvest from the plants at either end of each treatment to negate the border effects. We followed this same procedure each year of the experiment. As we recorded the yield, we divided the tomatoes into three grades. Grade “A” were tomatoes that had no blemish of any kind, grand “B” tomatoes had some type of blemish or deformity, but were still marketable and grade “C” were not good…unless you have a market for tomato soup.

We purchased a refractometer to measure the Brix (% Sucrose). Supposedly the higher Brix reading indicates higher sugar content, higher mineral content, higher protein content and a greater specific gravity or density. This adds up to a sweeter tasting, more minerally nutritious food with lower nitrate and water content. Crops with higher Brix should produce more alcohol from fermented sugars and be more resistant to insects. This should provide more disease resistance and be more nutritious for human consumption. We took a refractometer reading from one tomato at random from each different grade within a plot at each harvest. This was repeated each year of the experiment.

In the year 2001 we wanted to rotate in green beans so as not to build disease pressure by growing tomatoes three years in a row in the same place. We again took soil samples and took appropriate measure to fertilize. Unfortunately, due to reasons we can only guess at, we failed several times to have bean germination sufficient to have any results in any plot.

In the year 2002 we attempted to grow another tomato crop. We took soil samples and again fertilized as recommended. However, due to a series of very unlikely events a successful tomato crop was never established (sometimes that happens on a real farm). We did however plant a late crop of green beans, which gave us good data.

We decided to extend the experiment another year so we could compare the first year tomatoes with the last year tomatoes. Soil samples were again taken and fertilizer applied. Tomatoes were planted in May, and harvesting lasted from late July through the end of September.

People:
- We were assisted and advised by Carroll Montgomery, president of the Christian Agriculture Stewardship Institute
- Gaylord Moore, Regional Horticulture Extension Specialist in Green County for the University of Missouri.

Results:
The results are very interesting. It is interesting to note that in the first year the conventional fertility treatment easily produced more than the organic treatments. We find that after four years things seem to have turned around. In 2003 the organic treatments are much improved, while the conventional treatments have a lower yield and are now less than the organic plots. The no-fertility treatments also dropped in yield from the first to the fourth year. The highest yielding plot was #4, organic fertility with pesticide applications.

The results from the third year, our study on beans, do not show so clearly one treatment above another (see table 2). The “Plants/trt” column shows that there was not uniform germination in the different plots. This was at least partially due to a mole problem, but we are not certain that is the only factor. Since the conventional treatments had fewer plants, it is not surprising to see that the total oz per treatment is higher for the organic treatments. However, when we look at the yield in regards to oz/plant, we see that the conventional treatments yielded approximately twice as much as the organic treatment. One factor leading to this could be that since there were fewer plants in the conventional plots, the plants that were there had greater access to light, water and nutrients.

Table 2. 2002 Green Bean Yield
Treatment, Plants/trt, Total oz, oz/plant
1, 131, 135, 13.9
2, 64, 92, 24.3
3, 188, 97.5, 6
4, 124, 128.75, 12.8
5, 67, 127, 22.3
6, 68, 75.75, 11

Regarding pest control, it was also noted that the tomatoes has less disease problem in the organic plots during the fourth year (see table 3). Our main disease problem had always been early blight, which caused a premature ending to our tomato crop every year. During the final year I did not note any early blight in the organic plots, while there was some in treatment two and quite a bit in the no fertility treatments.

When we grew green beans none of the treatments had significant pest problems.

Table 3. Percent Grade A, B, C
Treatment, Grade, 2000, 2003
1, A, 4%, 8%
1, B, 54%, 97%
1, C, 42%, 25%
2, A, 6%, 1%
2, B, 69%, 73%
2, C, 25%, 26%
3, A, 7%, 0%
3, B, 54%, 76%
3, C, 39%, 24%
4, A, 3%, 6%
4, B, 80%, 69%
4, C, 17%, 25%
5, A, 3%, 2%
5, B, 44%, 76%
5, C, 24%, 22%
6, A, 1%, 4%
6, B, 66%, 80%
6, C, 33%, 16%

There was bug bite damage in all of the plots in the fourth year. Grasshoppers, cucumber beetles, and squash bugs caused some damage and there was some disease. This accounts for the tomatoes in grade C. We did not diagnose the specific diseases seen.

Discussion:
Upon examining the results of this study there are a number of things to learn. First, it is possible for an organic fertility system to help reduce pest problems – tomatoes in this case. We chose tomatoes because of the perennial disease problem that we had in them. Seeing healthy tomato plants at the end of September that had received no pesticide application was a great thing to see. In previous years all the tomato plants would have been dead by then.

We reviewed the results of the soil sample analysis and found surprisingly few differences from the first year to the last. There were some; phosphorus was higher in organic treatments the last year then the first, so was copper. So, what made the difference? We had no way of measuring soil biological life, but I think that was part of the difference. Part of the organic recommendations was the addition of live biological products every year.

It is also interesting the conventional fertility treatments had a drop in production. Was this a result of the chemical fertilizers? Certainly an experiment such as this could be carried on for several more years and something new could be learned each year.

Table 4. Refractometer Readings
Treatment, Grade, 2000, 2003
1, A, 3.1, 5.9
1, B, 5.4, 5.9
1, C, 2.3, 5.5
2, A, 5.1, 6
2, B, 5.3, 5.5
2, C, 4.8, 5.6
3, A, 4.9, NA
3, B, 5.2, 5.6
3, C, 4.7, 5.2
4, A, 5.2, 5.5
4, B, 5.6, 5.7
4, C, 5, 5.7
5, A, 5.5, 5.9
5, B, 5.8, 5.6
5, C, 5.4, 5.7
6, A, 1, 5.9
6, B, 5.4, 5.6
6, C, 5, 5.7

We did not see a correlation between the refractometer readings and yield quality or quantity (see table 4). Sometimes a grade C tomato which was severely diseased or eaten would have a relatively high refractometer reading. The readings for 2003 seemed generally to be higher than those of the year 2000, but again there was not much difference between grades or treatments. For tomatoes, 4 is considered a poor reading, 6 average, 8 good, and 12 excellent. Most of our tomatoes were close to an “average” reading, with a few closer to “poor”.

OUTREACH
The first year we had a field day and about 15 people came. Gaylord Moore and Carroll Montgomery, representing the two fertilization paradigms, gave presentations. Until this last summer when we closed our farm market, we informed many customers regarding this project and the SARE program.