From small seeds to big roots: no-till organic carrots in Maine

We all have biases. In research, we randomize things and establish clear rules to avoid having our biases influence results. But I have concluded that it doesn’t violate any rules of research for me to admit one bias: I like carrots better than spinach. After years of working with spinach as our primary spring vegetable crop in research (just look through this blog…), I was quite excited to no-till seed some carrots this spring in Maine and see how they’d do.

The treatments for this experiment were the same as the spinach I reported on a few weeks ago except that there was no May fertilizer application. The seed was unpelleted (var. Mokum). Before any graphs, a picture:

No-till carrots (left) seeded into forage radish “residue”, were fewer than carrots seeded into tilled seedbeds (middle and right), but they had a higher percentage of marketable roots. Fertilizer was in the form of mustardseed, soybean, and fish meal.

Sandy “carrot” soils like this present different management challenges compared to “heavier” textured soils. Reducing tillage is important for soil quality in all soil types.

This is a sandy, well-drained soil. I mention this because (and here’s another one of my biases…) soil changes everything and the differences between your soil and this one may lead to different results from those presented here.

No-till vs. Tilled

Some results were clearly a function of the seedbed preparation (no-till vs. tilled) and were unaffected by cover crop treatment (the three different fall radish seeding dates vs. no cover crop/weeds). Notably, the emergence was lower in the no-till treatments, but the marketability of carrot roots was higher.

Click for larger version.

The lower emergence seems to contradict the post I wrote about comparing seeders in Maryland. It could be any combination of physical factors (temperature, variable depth of seeding in the no-till surface, moisture) and biological factors (wireworms comes to mind given the observation that there was some wireworm damage on mature carrot roots).

Despite the lower emergence, there were many carrot seeds that did emerge in the no-till plots, indicating that the no-till conditions were not entirely limiting for carrots. Even those little teeny seeds can emerge in an untilled seedbed like this one.

One of the concerns with no-till crops is the potential for delayed maturity as a result of lower soil temperatures, slower nutrient mineralization, and (sometimes) higher bulk density. This has especially been a concern for root crops. In this soil in this spring, delayed maturity of no-till carrots was not evident. All the carrots were slow to grow compared to the stated days to maturity, but it was a slow, cold start to spring this year in Maine.

Cover crop, tillage, and fertilizer effects on carrot yield

FR1, FR2, and FR3 indicate the three fall plantings of forage radish. NC= no cover crop. The – fertilizer treatment had 50 lb N/acre as organic fertilizer added in fall to FR and at planting to NC. The + fertilizer treatment had an additional 50 lb N/acre added at planting in spring.

Sometimes the things that aren’t different are as striking as the things that are. From these yield data, one might assume that seeding date of forage radish in late summer/early fall is insignificant, but what these data don’t show are weed pressure. The third seeding date (FR3) at the very end of August did not provide good spring weed suppression, but weeding all plots with a hoe and by hand limited weed interference with carrot growth. This is important for interpreting the no cover crop (NC) yield data as well… though the data for weed pressure are not presented here, no-till seeding without herbicides into weeds is not advised!

It’s time to start seeding cover crops…

With August just around the corner, it’s time to start seeding forage radish in New England if you want to try this next year. I want a couple more years of data, but I’m almost ready to say I won’t grow spring carrots any other way.

Please contact me if you’re interested in trying any of this, or if you’ve already tried these systems. Share the good, the bad, and the ugly with me! I’m not so biased that I can’t take it.