Organic Fertilizers Have an Impact on Vegetable Crop Yield


How well do eggplant crops perform with organic fertilizers? Researchers are taking a close look at production results.

To badly quote Jane Austen, it’s a truth widely acknowledged that organic production is in need of a well-fed, healthy soil. To that end, researchers have turned their attention to understanding just how much organic fertilizers impact vegetable yields.

Check out two recent studies on the topic. One examines if organic acids can access soil’s natural phosphorus (P) content without adding mined P fertilizer. Another assesses how much organic fertilizers impact sweet onion yield.


Organic Fertilizer Rates Impact Sweet Onion Yield and Quality

With increased interest in organic fertilizers, researchers at the University of Georgia wanted to test if they have an impact on sweet onions.

Using five organic treatments during the 2012 to 2013 and 2013 to 2014 winters, the team found the sweet onion weight and yields increased “quadratically.”

In fact, the more fertilizer used, the higher the yields and weight, and the team didn’t reach a ceiling with the rates used in the study.

One drawback they discovered was in postharvest. The most common cause of postharvest bulb decay is botrytis rot.

Read the full study, “How Organic Fertilizer Rates Impact Sweet Onion Yield and Quality.” It requires a fee to access.

Organic Acids Can Help Crops Access Naturally Occurring Phosphorus in the Soil

USDA and Texas State University researchers noted the soil usually contains sufficient P to nourish crops. The only problem? It’s often bonded to other minerals, reducing its availability.

Organic acids release bonded P, thus increasing fertility, however. The research team set out to determine if yields improved on phosphorus-loving eggplant crops if they applied organic acids alone to soil. They then compared the results to eggplant treated with traditional fertilizers.

Here are the details of the trials:

Organic acids: The two organic acids were citric and oxalic and given in two different concentrations — 0.1 millimoles per litre and 100 millimoles per litre each.

Soil: The study also used soil from two Texas locations with significantly different soil types. One is from the Houston area. That soil had a 7.8 pH, high levels of calcium, and calcium carbonates.

The other soil came from a location between Austin and San Antonio, with a 6.6 pH.

Results: The Houston-area soil showed just slightly lower P levels than the soils treated with conventional P fertilizers. There was no significant difference in yield. The soil taken from the second location did not have as strong a result.

Since the Houston-area soil had high amounts of calcium-bonded P, the researchers believe the organic acids had more opportunity to release P and, therefore, those soils had better results.

The researchers also speculate that pH below 7.0 results in more P retention and decreased P mobility.

Read the full study, “Effects of Organic Acids Application on Olsen-Extractable P and Eggplant (Solanum melongena) Yield.”