Our farm receive a SARE grant in order to pursue research with respect to the spacing of dissimilar cash crops in the same planting. We have some preliminary results which we shared at the Small Farm Conference in Missouri a few days ago. We thought it might be enjoyable to give a summary here so everyone can see a little of what we are doing.
Some assumptions on which we based the research:
- Intercropping (also known as companion planting) can be beneficial for the health of both crops in that it can help control pests and diseases.
- If a small vegetable farm wants to 'scale up' their operation, they must find ways to become more efficient in handling their labor/farm tasks.
- Monocropping (growing one crop exclusively in a field) has gained acceptance because it is difficult to figure out how to intercrop AND increase farm efficiency.
Can we identify intercropping spacings that will allow us to automate some of the operations that have been very hand labor intensive up to this point on our farm? One could consider these efforts an attempt to provide a 'proof of concept' for the idea.
There were, of course, sub-questions. And, you can make arguments about how research should be conducted - but that only derails us here. The point of the matter is that we have to identify proof of concept in order to open the way for increasingly focused study.
Potatoes and Beans
One of the fields that received our attention for this study was our potato/bean field. We have long been convinced that bush beans (in particular green beans) have a masking effect that prevents Colorado potato beetles from finding potatoes. We want to maintain the benefit of this pairing, but add some mechanized cultivation to reduce labor time and cost.
Treatment (new tractor spacing)
The photo shown above was taken in July of this year. You can see each "bed" has wheel tracks that match the width of our Ford 8n tractor. The area between the wheels is approximately 40 inches. In each row, you will see the broader and lighter colored bean plants on the left. The potatoes are on the right.
The wheel tracks are very clean, as are the beds. The plants formed a solid canopy and coexisted well.
Control (old spacing)
Our old spacing was implemented using a walk behind tiller. The space between potato rows is approximately 6 feet, with a double bean row in between each. The double bean row consists of two seeded rows that are about 8 inches apart. If you look carefully, you can see there is a path between each row.
Weeding between rows - New Spacing Wins
Clearly, the reduced number of paths to maintain for weeds in the tractor spacing is a win. It is also a win when you realize you can use a cultivator behind the tractor to get those paths weeded.
In Row Weeding - Inconclusive
If you consider 'sides' of each row you have to weed, you actually have 'less' with the tractor spacing. But, we also found that the last weeds caught up with us in row for the tractor side. This would be, in part, because the potatoes started to die off. But, it was largely because it was slightly more difficult to weed by hand in the tractor spacing. The net result was that we seemed to do better early in the season with the tractor spacing and better later in the season with the old method. But, with all of that said, there were some mitigating factors that we can attribute to our drought year that may have something to do with it as well. So, we're unwilling to make a conclusion on this one.
Mulching - Edge to New Spacing
This one is a bit difficult to state since we simply didn't have the grass/straw mulch available to us this past season. But, we did have some in the first year of the study. The new spacing should use less of the mulch. The only issue being the effort getting mulch between the beans and potatoes in the tractor spacing. But, since we have done double bean rows, this wasn't much of a new problem. Typically, we just let the canopy handle that area.
Irrigation - Edge to New Spacing
A single line of drip tape for a row of potatoes combined with beans. In the old spacing, we needed a line of drip tape for every row. This would reduce our use of drip tape by about 1200 feet in this plot alone. On the other hand, you have to realize that the irrigation spread may not be perfect for both the beans and potatoes. And, in a dry year, they may try to move into the 'wet zone' and compete for the water and nutrients. But, we didn't see much problem in those areas.
Pest Control - Tie
First - we did note Colorado potato beetle presence this year on our farm. They appeared both in potatoes and eggplant in very small numbers. But, the great news is that we only noted them on the edges of the field, where the proximity to beans would be lessened. We also grow bush beans near our eggplant and noted similar results. What this tells us is that either spacing technique appears to be sufficient in providing pest control.
Yield Potatoes - Tie
We noted that the yield of Purple Majesty potatoes in both were nearly exactly the same in terms of pounds per foot harvested. Rio Grande (russet) was a bit lower in the tractor spacing than in the traditional spacing. However, we noted some anomalies in East end of the tractor spacing that likely account for the difference. Even so, the reduction was not statistically significant.
Yield Beans - Tie (sort of)
We grew two varieties of green beans that were tested. Provider is an earlier, 'peak crop' variety. Jade is a later, 'long season crop' variety. Essentially, Provider is known to give a large harvest over a short window and Jade, once it starts, gives lighter crops per pick, but over a longer period of time.
We found that Provider actually produced a similar amount in both sections in terms of total weight. This is also true in terms of row feet. However, you must remember that the old spacing ran Provider in a double row. That means we dropped twice the amount of seed into the old spacing in order to get the same harvest levels. In other words, our production per SEED foot was halved.
On the other hand, Jade produced nearly double the total weight per row foot in the old spacing than it did in the new spacing. In other words, it produced the same amount per SEED foot in each spacing. It did not seem to care about the relative proximity of its neighboring row of plants. Nor did it seem to care if it was a potato or a bean.
It would seem then, that we can declare a possible win for the old spacing here, until you consider how many rows we can plant for beans in each spacing. We can run 14 rows of beans in the tractor spacing and only 10 with the old spacing. Of course, that would mean 10 double rows of Jade versus 14 single rows. But, if you can't keep these rows weeded, the point is moot. And, of course, this assumes you only wish to grow Jade as your only green bean. If you want an earlier crop, you might prefer Provider, making the tractor spacing superior in terms of seed use.
Brassica and Allium
We also ran spacing trials on this field. The top picture shows our tractor spacing and the bottom shows our traditional spacing. Perhaps we'll discuss this one later.