The modern factory food industry which nourishes many of the world's 7.6 billion people demands large supplies of wheat, corn, sugar and soybeans.

The ranches on the plains of Brazil, Russia, China, India and the US churning out these key commodities depend, in turn, on industrial fertilizers.

Now, however, big farming and fertilizer firms face several challenges: Regulators are enforcing stricter rules to protect the environment. Consumers are buying more organic foods. And we're eating less.

Global food demand is expected to increase more slowly next decade, according to the Food and Agriculture Organization. Demand is now driven by population growth, instead of per capita consumption, the FAO says.

The upshot: The modest growth of fertilizer consumption this year "reflects a combination of relatively low but slightly increasing international prices for most agricultural commodities," the International Fertilizer Association said in a report this summer.

To be sure, selling and shipping fertilizers will never be as attractive a proposition as trading iron ore or copper. Total global trade is around $40 billion a year, less than half the worth of iron ore. And it's a tough industry to consolidate, with thousands of producers around the world, high shipping costs, and widespread demand.

But it's still a big, profitable business, vital business for modern agriculture, and an opportunity for shipping lines, logistics firms and commodity-trading firms. The total global market is worth around $200 billion.

The dominant method of making fertilizer is a complicated chemical process used to make a gas called ammonia that relies on natural gas. That's why big natural gas producers like the US, Russia, Belarus and Qatar are also big producers and exporters of fertilizers.

Top exporters of fertilizer, first 7 months, 2018

• Russia $4.4 billion (+10%)
• China $3.3 billion* (NA)
• Canada $3.1 billion (+15%)
• US $2.4 billion (+4.7%)
• Morocco $1.8 billion (+30%)
• Belarus $1.7 billion (+15%)
• Germany $1.5 billion (+6.4%)
• Belgium $1.3 billion (+21%)
• Netherlands $1.2 billion (-2.7%)
• Qatar $777.8 million (+39%)

*2017 figure. Full Chinese data not available.

Nitrogen fertilizers are usually obtained from natural gas, but can also come from manure, garbage and sewage. In Jamaica, a nitrogen-based fertilizer is even made from bat guano.

The main form of nitrogen fertilizer, of course, is ammonia, which can be applied as a pressurized liquid. Global capacity is expected to increase by 8% in the next four years, according to the US Geological Survey. "Increased demand for ammonia is expected in Latin America and South Asia as a result of regional nitrogen deficits," the USGS said. "Large corn plantings increase the demand for nitrogen fertilizers."

A second big category of fertilizer production is via the mining of potash and phosphates.

Potassium fertilizers are mined from potash deposits, vast ores of sediment left behind hundreds of millions of years ago when massive lakes evaporated.

Mining companies dig thousands of feet to unearth potash, which is derived from the Dutch "Potasch", which originally meant wood ash. It was a key industrial chemical as far back as the 18^th century. In the 1940s, potash was discovered in Saskatchewan while drilling for oil, cementing Canada's position as the world's top supplier.

The world's biggest fertilizer company, Nutrien, is still headquartered in Saskatchewan. Canada's top markets are the US, Indonesia, India, China and Malaysia.

Canadian fertilizer exports, first 8 months, 2009-2018

• 2009: 5.1 billion kg
• 2010: 10.9 billion kg
• 2011: 12.8 billion kg
• 2012: 10.8 billion kg
• 2013: 12.1 billion kg
• 2014: 11.8 billion kg
• 2015: 12.7 billion kg
• 2016: 10.3 billion kg
• 2017: 12.8 billion kg
• 2018: 13.9 billion kg

Morocco is a large producer of fertilizers because of its voluminous reserves of phosphate rock that can be mined in the Western Sahara, which it still occupies, despite protests. Morocco holds almost three-quarters of the world's total phosphate reserves.

Phosphorous fertilizer comes from phosphate rock or bones. World mine capacity, not counting China, is expected to grow to over 165 million tons in 2021 from 147 million tons in 2017, thanks to increases in Egypt, Jordan, Morocco, Senegal and Turkey. Production of phosphate rock in China is around 80 million a year.

The biggest market for fertilizers is in Asia, which accounts for around 45% of total demand, because of massive farms in India and China.

Top importers of fertilizer, first 7 months, 2018

• US $3.9 billion (+5%)
• Brazil $3.6 billion (-13%)
• India $3.4 billion (+63%)
• China $1.4 billion* (NA)
• France $1.1 billion (+6%)
• Thailand $1.1 billion (-1.4%)
• Australia $1 billion (+8%)
• Mexico $939.9 million (+5%)
• Turkey $902 million (+10%)
• Belgium $770 million (+14%)

*2017 figure. Full Chinese data not available.

Many fertilizers are made from a mix of nitrogen, phosphates and potassium. Modern farms use a variety of machines to apply synthetic fertilizer in solid, gaseous, or liquid form. Brazil, which has massive farms and a fertilizer deficit, is the world's top market outside the US. Its imports have declined in 2018 compared to the same period in 2017.

Brazil fertilizer imports, first 7 months, 2009-2018

• 2009: $1.7 billion
• 2010: $2.3 billion
• 2011: $4.5 billion
• 2012: $3.8 billion
• 2013: $4.9 billion
• 2014: $4.3 billion
• 2015: $3.6 billion
• 2016: $3.2 billion
• 2017: $4.2 billion
• 2018: $3.6 billion

However, newly elected president Jair Bolsnaro is expected to push the expansion of large-scale soybean and sugar cane farms, which should boost fertilizer imports.