DR. Don Research Update
Crop productivity products don’t always work – but need more evaluation

By Don Lotter

June 1, 2004: The bewildering array of crop productivity products out there is badly in need of rigorous, systematic comparative evaluation. A small, and unfortunately flawed, start has been made by Oregon State University researchers on one crop in one location, evaluating 15 products.

The researchers found that there were no significant differences between any of the treatments, including the control.

The plant productivity products were: humic acid products, Norwegian kelp concentrate, a nitrogen fixing bacteria, plant growth regulators (cytokinen and ammonium zinc acetate), and various organic fertilizers.

The products of nine companies were evaluated in 15 treatments in an onion crop. Each treatment generally consisted of a combination of products from one company. The products were too numerous to list here.

According to the researchers, humic acids in the humic acid products were far below the 75 kg / ha rate recommended in humic acid research. With the exception of one product at 31.4 kg / ha, the others averaged less than 5 kg / ha. To attain the recommended 75 kg / ha, some of the humic acid products would cost over $1000 / ha.

The only foliar-applied humic acid product supplied humic acid at only 1/10th of the recommended foliar rate of 0.5 kg / ha.

For micronutrients, with the exception of one product, all of the foliar-applied products supplied micronutrients at far below the recommended rates.

The nitrogen fixing bacteria inoculant didn’t give results because all of the plots were fertilized with nitrogen fertilizer.

Kelp extracts had no effect on yield or size classification of the onions.

While this research is helpful in giving some perspective on plant productivity products, there are a number of deficiencies in the work. The most glaring is that no consideration was given to sensory quality or for shelf-life. Lots of anecdotal evidence, and some research, suggests that kelp products have an effect on sensory quality and shelf-life of fruit and vegetable crops.

Many plant productivity products improve yields where crops are stressed – either by disease, insect attack, difficult soils etc. The onion crop in this research was grown under optimum conditions.

As far as the “active ingredients” being far below the recommended rates, well, this may or may not be relevant. It is like doing a chemical analysis on a biological inoculant and saying that the NPK levels are far below those recommended. The ingredients might be synergistic with each other in small amounts.

However, it does seem that the humic acid products were coming up awfully low on humic acids. We need more research to be done to answer these questions.

It should also be taken into consideration that organic crops may react differently to these products than conventionally grown crops do. Organic crops are much more underpinned by biological processes, which may respond quite differently to these products.

The same kind of research as this needs to be done on at least another 100-200 products, on dozens of crops, in different regions, in different conditions of stress.

Source:
Feibert, E. et al. 2003. Nonconventional additives leave onion yield and quality unchanged. HortScience 38(3):381-386.

Don Lotter has a Ph.D. in agroecology and has worked in sustainable agricultural development in North America, Latin America, and Africa over the past 25 years. He can be contacted via his website www.donlotter.com


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