That's ag snark for Unconfirmed Field Observations. It's the bedrock of "alternative agriculture" (alternative to what?), organic advocacy etc. Robert asks some pointed questions about one example of UFOs in rice cropping.

[The System of Rice Intensification] SRI is a system which consists of transplanting widely spaced very young individual rice plants, using organic fertilizers, and not permanently saturating the fields with water. . .

The BBC reported a doubling of yields in Nepal. . .

In a rather thorough review, in 2006, McDonald, Hobbs and Riha found that it sometimes works (in Madagascar), but that generally yields are 11% lower with SRI, not higher.

What is one to think then? Do newspapers blindly follow NGOs, and do farmers say what is scripted? Another case of overselling? Or is this a true farmer/priest led breakthrough, which scientist at fancy universities and research institutes just do not get? . . .

When SRI ‘works’, it is hard to know what farmers really did. Perhaps planting density was not quite that low, and organic fertilizer were applied at very high. What is SRI being compared with anyway? A degenerate farm, or a fully optimized ‘modern’ farm?

There is some research support for sparse planting and low fertilization. It has been found that in some cases maize yields are nearly as high on a per plant basis in such fields, even though the plants themselves seem stunted. Apparently fertility goes into the production of leaves and stems when it is plentiful but when it is scarce the plants sacrifice leaves for seed and still make good grain heads.

There is some support for "organic fertilizer" when compared with unbalanced fertility. Manures and composts contain many of the 16 primary and secondary nutrients, many of whch are not included in simple fertilizer concentrates. Often these concentrates have nothing but nitrogen, which is essential but only part of a plant's nutritional needs.

Good farmers do develop idiosyncratic yet effective systems that fit their particular circumstances, and often can't explain their methods in ways that academic researchers can grasp. They have wildly divergent frames of reference from researchers, and don't always have controlled experimentation results to separate the effective parts of the method from irrelevancies.

The real trouble comes from the creeps and cranks - the NGOs and activists - that trumpet wild claims that seem to support their biases. This polarizes what could and should be an open dialog between practitioners and researchers, alienating one from the other for instrumental reasons. This is happening now with biochar as the creeps belatedly twig to the benefits and potentials of its manufacture and use. I expect this to become a sort of litmus test in future for rationality. If you speak well of biochar you will be stigmatized due to the idiotic claims now being made by cranks, though there are real benefits to its use.

The IRRI analysis cited in the referenced post makes some debateable points.

Three components of the SRI strategy run directly counter to well-established principles for high crop growth. These principles were developed over many years of careful testing and scrutiny by scientists worldwide, and they have stood the test of time.

First, SRI uses very low plant densities. Energy for crop growth results from intercepted sunlight, and the amount of light intercepted translates directly into plant growth. High plant density enhances light interception, growth and yield. SRI suffers from poor light interception because of low plant densities.

Second, SRI replaces paddy flooding by simply maintaining “moist” soil conditions. The physiology and physics of plant water use have been researched for more than 300 years, and the relationship between growth and plant water use is unambiguous. Ample water maximizes rice yields, and flooded paddy fields assure that no water limitations develop.

Third, SRI emphasizes organic nutrient to the exclusion of mineral fertilizer. SRI faces a serious challenge in obtaining sufficient mineral nutrients from organic sources to achieve high yields. Rice grains contain about 0.013 grams of nitrogen per gram of seed (1.3% N). A claimed yield of 15 t/ha requires nitrogen from over 50 t/ha of organic matter. Such a monumental demand for organic matter creates huge challenges in sourcing, handling and managing these materials.

First, it isn't plant growth that matters so much as grain growth. In some cases, such as the maize example given earlier, grain production is not always proportional to biomass (leaf and stem) production.

Second, it may be difficult and time consuming, but maintaining ample water can be done without flooding.

But the third point is telling. The truly massive amounts of imported manures that would be needed to provide the nitrogen embodied in the rice grains - not to mention some unavoidable loss to denitrifying bacteria, leaching etc.; and plant overhead for leaf, root and stem growth - makes the claims seem ridiculous. One way that it might work is if there are hidden nitrogen sources such as in the water used to irrigate. This isn't that uncommon and sophisticated growers analyze their water and work its characteristics into their fertility calculations. Still, I suspect that even with all of these caveats the claimed yields are improbable.