Science on the Farm

We haven’t spoken much about science on the farm, but we’ve had a number of projects going over the last few years. Last season, KCC Urban Farm┬áran a small experiment to see how adding minerals to our soil could boost plant nutrition. This year, we plan to expand upon that experiment, so stay tuned for internship opportunities!

The problem:
Soil is made out of minerals (50%), air (23%), water (23%), and organic matter (4%). Because KCC Urban Farm is lucky enough to receive donations of compost from the Department of Sanitation, however, our soil has 30% organic matter! What does this mean for us? For growing our high quality vegetables, it means we have to test our soil for the nutrients plants need to grow.

The solution:
Based on the soil test results, we can add mineral amendments based on what we’re missing.

The experiment:

Student research assistant Adriana Valerio measuring brix in kale leaves

Student research assistant Adriana Valerio measuring brix in kale leaves

We want to know if our mineral amendments are leading to healthier crops. In 2014, we ran a small experiment on our tomato plants: we amended only half of the plants for each variety of tomato. After a couple of weeks, we measured calcium and brix levels in new and old leaves for all of the tomato plants. We did the same thing a couple of months later. Calcium is important for plant growth – plant cells use it for structure. It’s also a good indicator of nutrient uptake. Brix is a measure of plant sugars – if brix is high, we know our plants have everything they need to thrive.

The results:
Our amendments increased calcium in our plants, but not brix:

CalciumAvgs

Calcium averages by raised bed (ppm)

BrixAvgs

Brix averages by raised bed

We have two theories as to why this is the case:

  • Three out of the four tomato beds were in the hoop house (H1, H2, and H3) – meaning they didn’t get any rain. This could have affected how much of the soil amendments actually soaked through to the plant roots.
  • We only added amendments once. Next time around, we will send the soil to a lab again, and amend again as needed. Maybe the plants needed more!

Discussion
2015 will give us an opportunity to expand on this pilot project. We plan to amend the soil and measure results for multiple crops, not just tomatoes, and to test our soil again mid-season to assess nutrient need when our plants need it the most.