It really does seem tragic that people need to make their own mistakes, rather than learn from others’. Latest case in point: soils in China are being destroyed by excessive use of fertilizers, which is making the soils too acid to support plant growth. Yields have already dropped 30-50% in some places. The conclusion that profligate and ignorant use of fertilizers comes from a paper published in Science by F.S. Zhang at China Agricultural University in Beijing and colleagues. That is behind a paywall, but there is a report in Nature News.
“They see the green leaves but they don’t see the impact on the soil. If they have a poor crop they think more fertilizer is needed, making matters worse,” Zhang says. Farmers routinely apply double and sometimes triple the necessary amount, he says. Better education could provide a simple solution to the fertilization problem.
People who promote “more fertilizers” as a panacea should consider that they need to deliver more than merely fertilizers.
God – that’s terrible. Farmers of Forty Centuries blow it in a few decades. They’ll be needing a lot more land – somewhere else and soon. Any spare continents going?
It is always difficult to make inferences from an article from which we only have a summary, or a journalist’s take destined to attract media attention. In the case at issue, the solution lies in education – as the summary rightly says –, devices to measure the appropriate level of N fertilisation, and liming.
As to the paper in Afrol News, which presents a study by colleagues in the International Institute of Tropical Agriculture (IITA), it advocates moderate use of fertilisers, which would make it “Easy to double African banana yields”:
“The study found that majority of the banana growers in the region do not use fertilisers at all. Growers thus, they conclude, were missing out on the opportunity to maximise the crop’s food security and economic potentials. Even a “moderate application of mineral fertilisers could double the production of the crop,” field studies had shown.”
And the authors of the paper and experiments are very conscious of the fact that more than merely fertilizers needs to be delivered.
From what I could see farmers doing in Yunnan and Qinghai several years ago, 40 centuries of experience with fertilisers is still going strong.
Very impressive recycling of nutrients is common practice in the Chinese countryside.
Excessive use of nitrogen fertilisers hurts the hip pocket nerve, particularly if it does not translate into expected yield increases. It looks like some Chinese farmers are “learning by doing” about modern fertilisers. That is a valid learning strategy, highly valued in the adult learning field.
Soil acidification can be rectified by liming, so it is not such a big problem, just an extra cost which can be avoided as part of the learning experience.
Any downstream or off farm effects such as eutrophication of water ways are likely to be a bigger problem, since it is often difficult for people to see the connection between their actions and the ecological effect.
Speaking of which, wasting N fertilisers also increases CO2 emissions.
The Science paper shows significant acidification (lower pH), but I couldn’t find anything in it linking that to decreased yields. The soils aren’t nearly acid enough to hurt plants directly, but aluminum toxicity increases at lower pH. Acidification can also affect pathogens; in one long-term experiment at Rothamsted, fertilizer-induced acidification allowed a pathogen to become established, causing such severe yield losses that the experiment was abandoned — after 80 years!
Thanks for the further details. I guess I was taken in by Nature’s version of the story, and without access to the original in Science that is really all I had.
So, everything is hunky dory in China and those yield drops, as reported in Nature, are not in the Science paper?
There may be yield drops, and the authors may think fertilizer acidification is responsible. But the Science paper doesn’t have any data on yield decreases or their causes. The figure of 30-50% did appear:
“N use efficiencies of only 30 to 50%”
(i.e. farmers are fertilizing up in the diminishing-returns zone)
but I wouldn’t think Nature reporters would mistake that for a yield decrease. They do discuss liming and argue that, at such high fertilizer rates, lime costs would be high.
As I recall from “Long-Term Experiments in Agricultural and Ecological Sciences”, documented yield decreases caused by fertilizer are rare in long-term experiments. Organic amendments are usually better, if available, but not replacing harvested nutrients is a sure way to decrease yield. In the Rothamsted experiment mentioned above, the no-fertilizer treatment crashed much sooner than than fertilized one.
On the other hand, fertilizer use can temporarily mask soil degradation from erosion, etc.