The Plant Nutrient "They" Don't Want You to Know About

I doubt anybody actually doesn't want you to know about Silicon - I just have to come up with interesting titles here.  If you look at your basic textbook list of essential plant nutrients you usually see something like this:

No Silicon on the list, and yet from an LSU article on Silica and Rice Growth, we can see that up to 8% of rice straw is ... Silicon.  Now it's not exactly breaking news that plant's use Silicon.  As early as 1867 German scientists suspected it helped prevent grains from lodging.  In his 1993 article, The anomaly of silicon in plant biology, Emanuel Epstein notes there are clear benefits to Si, but wrestles with the idea of being able to define it as "essential".

The problem with the term "essential" that it is possible to grow plants to maturity in mediums where Silicon has been completely excluded.  The catch though is that these plants are rather pathetic compared to plants that have access to Silicon.  As Epstein writes in his 1999 paper aptly titled, Silicon, 

"[Silicon deprived plants] are often structurally weaker than silicon-replete plants, abnormal in growth, development, viability, and reproduction, more susceptible to such abiotic stresses as metal toxicities, and easier prey to disease organisms and to herbivores ranging from phytophagous insects to mammals."

So although Silicon is not essential for some plants in that they can conceivably live without it in a laboratory, it is possible these plants would not survive environmental stresses in their natural habitat without Silicon.   Adding further confusion to the "essential" debate is the fact that "for certain algae, including prominently the diatoms, and the Equisetaceae " Silicon is indeed an essential nutrient, without which these plants would not grow.  By 2005, Epstein and Bloom settle on the term "quasi - essential"

The takeaway from all of this is that although semantics prevent Silicon from being defined as an essential plant nutrient, it's safe to say it's rather important for a healthy plant.  It's benefits range from greater resistance to drought and pest stress to stronger cell walls (which is what helps prevent the lodging those Germans were talking about). The proof is in the pudding of course so here are some pictures from Janislampi's 2012 paper, Effect of Silicon on Plant Growth and Drought

Stress Tolerance.  Check out the artilce for more pictures.

And although the world of plant nutrition may not have fully embraced silicon's importance, cannabis nutrient companies are all over it.

In time I think the table of essential plant nutrients from the very beginning of this post will be but a relic.  Until then, don't forget to give Silicon the credit it's due!

Fertilizer Subsidies in Malawi

From the great NY Times article on the subsidy program.
The "Billions of metric tons" is an error though and should
say millions.

The recent success of Malawi's fertilizer subsidy program is a perfect example of the role that soil can play in the well being of a state.  In the early 2000s, Malawi faced grave challenges feeding itself.  In 2005, over a third of its population, 5 million people in a country of 13 million, needed emergency food aid. Only 1.2 million metric tons had been produced in that years dismal corn harvest.  Yet the very next year in 2006 the nation had a record harvest - 2.6 million metric tons of corn. One year later this new record was smashed when farmers harvested 3.2 million metric tons.  The increase in production has been maintained as well, with 2013's corn harvest coming in at 3.6 million metric tons.  How did the nation pull itself back from the brink of famine so effectively?  Increased soil fertility.

In 2006 Malawi initiated its Farm Input Subsidy Program or FISP.  The program subsidized several inputs, the main ones being fertilizer and seed.  Two fertilizers were provided at reduced cost to farmers, Urea with 46-0-0 and NPK 23-21-0 +4S. Despite its name, the NPK fertilizer has no Potassium although it does contain Sulfur.  Fertilizer use increased dramatically due to the program and as a consequence farmers obtained record yields.

Not only did this mean that there would be adequate supplies of food for the population, but for an agrarian nation like Malawi, such an impressive jump in production can really boost the economy. Indeed, many observers have credited the implementation of the subsidy program for the country's economic growth with GDP almost doubling between 2005 and 2011. The FAO stats on agriculture production show a clear trend.  Before the FISP in 2005 Malawi produced $150 million of corn and roughly the same value of tobacco, by 2012 those figures had risen to$430 million worth of corn and $240 million worth of tobacco.  It is important to note here that the majority of corn produced is consumed locally, but tobacco harvests, an important export crop for Malawi, clearly benefited from increased use of fertilizer.

There's nothing like a side by side crop comparisons to drive home the impact of the program.

Corn field with fertilizer on the right, without on the left. Malawi 2007. Source Duffel

Corn in the foreground without fertilizer, corn in the background with fertilizer.  From Ntchisi, Malawi 2009.  Note that you can see a trademark foliar symptom of N deficiency on the corn leaf just above the "Nt" where "Ntchisi" is written in the first line of this caption.  The lower leaf shows chlorosis, but in an arrow like streak that goes down the center of the leaf.  K deficiency on the other hand usually presents itself as chlorosis on lower leafs but more on the edge and without the arrow streak down the center.

Corn produciton now is sufficient to feed Malawi's population
This chart from a study documenting the FISP.

It seems safe to say that Farm Inpust Subsidy Program succeeded in increasing corn production and spurring economic growth.  The country now no longer lives with the threat of famine and (huge understatement here) this makes for a much more stable nation state.

The future of Malawi's soils management

There are problems with the program however and I think the critiques can be put into two categories. There are issues with prolonged use of urea fertilizer and soil health and then there are concerns about the levels of government spending to support the subsidy program.  There is also the problem of malnutrition due to over dependence on corn (Malawi is the third highest per capita consumer), but this is not necessarily the direct fault of the FISP.

The government currently spends a good deal on the subsidy program, somewhere around 9% of government spending.  As one Oxfam blog points out, while one ton of imported corn can support five families for 96 days, the same amount of money spent on fertilizer subsidies would allow them to produce enough food for 10 months.  Clearly producing corn isn't quite as simple as subsidizing fertilizer but the point is valid- it makes more sense to invest in fertilizer when the alternative is importing food from abroad.  Things get tricky when the price of synthetic nitrogen fertilizer increases as it did in 2008.  The program costs jumped from a little over $100 million to around $225 million.

The production of urea is a rather energy intensive endeavour, requiring 2-3% of the world's annual production of natural gas.  Increasing demand for synthetic nitrogen and finite supply of natural gas means the cost of urea will continue to rise.  This begs the question, when will Malawi no longer be able to afford its subsidy program.  It also begs the question, when will we all starve if we continue to rely on synthetic N to feed ourselves, but that's a whole other blog post!

Olivier de Schutter, UN Special Rapporteur on the Right to Food, has also lamented how the FISP swallows up more than half of Malawi's agricultural budget and prevents investments in more sustainable approaches to increasing yields.  He gives us a nice segueway to the other major problem with the FISP in this news clipping:

“It is time for Malawi to move beyond the fertilizer-led “green revolution” and invest in the Brown and Blue Revolutions needed to rebuild soil fertility and water retention,” the Special Rapporteur urged. He noted that the integration of legumes in cropping systems and agroforestry systems in Malawi are yielding more food than fertilizer-driven systems while rapidly restoring soil fertility. They are the foundations of sustainable food security. He emphasized the need to move away from the maize economy, and to link agricultural development to nutritional needs, an indispensable condition for lasting victories over malnutrition.

Prolonged use of urea fertilizer has been shown to acidify soil, decrease cation exchange capacity, and decrease exhangeable Calcium and Magnesium.  Using only Nitrogen, Phosphorus and Sulfur as the sole fertility inputs on fields while extracting record breaking yield of corn from the soil will surely lead to demineralization.  All the other essential plant nutrients other than N, P and S that are being removed from the soil with each harvest are not being replaced with the current fertilizer regime.  So although the FISP is clearly boosting productivity, it relies upon constant input of chemical fertilizers year after year, and at the expense of long term soil health.  There is no improvement of soil fertility here beyond the year the fertilizer is applied as opposed to cropping systems which apply substantial amounts of organic matter. If the FISP were to stop, the legume and agroforestry systems that de Schutter metnions would be able to continue producing while the soils dependent on chemical inputs would see yields collapse.

Don't get me wrong, the synthetic fertilizers of the subsidy program are currently what feed Malawi and credit should be given where it's due.  However the simple fact that the FISP is the only thing standing between Malawians and famine points to the need for a more enduring solution to improved soil fertility that ideally is accessible to farmers without government intervention.  The enduring solution is of course alternative pathways to soil fertility that don't rely on imported chemical fertilizers that no one can actually afford on their own.  Legume cropping systems, agroforestry, composting, proper recycling of human waste, and the recapture of fertility from other waste streams will all have to become more important.  Urea is an extremely convenient source of fertility for the end user, a 50 kilogram sack that is 46% N by weight.  However onsidering the complicated process required to make this product puts this supposed convenience into perspective.  Alternative sources of fertility will also need to be relatively complex in that a series of complimentary components will be needed.  One single source will not be sufficient in order to meet the demand that synthetic fertilizers currently satisfy.  Just as the Green Revolution depended on multiple innovations in order to function, so to will any attempt to replace chemical fertilizers.  Wether one supports the use of chemical ferilizers or not, the facts stand that they feed much of the world and we will not have access to them forever.

Faidherbia albida - a nitrogen fixing tree.   The tree's ability to increase the fertility of the surrounding soil is evident in the picture.