Over it! Study Shows Cover Crops And Organic Fertilizer Improve Zucchini Yield

By Jonathan Parker

Finding the proper combination and rotation of crops can be a challenge in any given farming system. Permaculture enthusiasts will be familiar with the idea of cover crops.

Cover crops are grown below, between, next to and sometimes even over the primary growth. They prevent weeds from taking hold, help provide proper nutrition in the soil and if chosen correctly, can even control pests and certain plant diseases.

Vetch, grown for thousands of years, is one of the most popular cover crop families. Recently in Italy, an experiment was undertaken that measured the effects of vetch cover crops and natural fertilizers on organic zucchini.

With a cover crop such as vetch, the timing of the growing cycle and methods of laying the cover are crucial. Typically, the cover crop has an earlier cycle; and as the time approaches to plant the primary seeds, the crop is rolled or mowed down to create a thick layer of natural mulch that the next crop can be sown in. This process creates a protective layer that serves multiple purposes. Rather than exposure to the elements, the soil is covered, preventing erosion. Weeds are stifled and the soil remains moist and fertile while the new seed germinates.

Terminating cover crops via the roller-crimper method is a common practice, but as mentioned above, the timeline for planting cover crops, crushing them, and planting the primary crop can be difficult to manage. Incorrectly managed cover crops can throw off the balance of nitrogen in the soil which can lead to poor plant nutrition and drastically affect yield. Experienced (crop coverers?) not only time the application carefully, but occasionally treat the nitrogen imbalance with organic soil supplements to keep the levels in check.

The study referenced was originally published in HortScience in August. It outlined the various methods of vetch management and the use of different organic fertilizers in varied combinations, and how these different processes affected the organic zucchini crop they were used on. The different fertilizers used were solid waste composts, anaerobic digestate (the remains of biodegradable feed stock) and commercial organic fertilizer. The process was laid out and examined for two seasons with a focus on the yield, quality of the crops and the nutritional changes in the soil.

At the end of the experiment the scientists involved had this to say

“Our results showed that zucchini yield was influenced positively by the vetch residue management strategy, although the response was significantly different between years. The vetch cover crop increased marketable zucchini yield in the first year by 46.6% compared with the fallow treatment, indicating that this fertility-building crop could reduce off-farm nitrogen (N) fertilizer input for subsequent crops. Averaging over 2 years of the experiment, marketable zucchini yield increased by 15.2% and 38% with the roller-crimper mulch and green manure plow-down, respectively, compared with the fallow treatment, although differences were significant only in the first year. 

An unfertilized area of zucchini crop was maintained as a control. In the first year the difference in yield between the two was significant, with the organically fertilized crop outperforming the control by over 20%. As mentioned earlier, the careful attention paid to the cycle of the vetch and the nitrogen in the soil paid off. The scientists only used about half of the fertilizer normally required for a field that size, based on their soil study. Francesco Montemurro, the lead author of the study noted “The greatest yield response was obtained in the green manure treatment, probably as a result of high above-ground biomass production that, when incorporated into soil, progressively mineralized and increased the available N content.

It was also noted that the variances in the 2 years was attributable to weather patterns and environmental factors. Cover crops, organic fertilizers and soil supplements can be susceptible to unfavorable conditions. The study was still extremely interesting and the scientists that participated are recommending further research on the long-term affect of these practices.

It’s good to see science taking a positive role in the management of old technology and the development of new organic methods of farming. Positive findings like this show that we are not as dependent on bio-engineering and chemical fertilizers as some organizations would have you believe. You can read the complete study HERE

Jonathan Parker is an EMT-Paramedic and Preparedness Instructor with a love for emergency medicine, self-sufficiency and homesteading. His goal is to empower people towards a natural and sustainable lifestyle.