WHAT color is Xinjiang? Satellite images reveal mainly three colors: white from glaciated mountains, green from grasslands and forests and yellow from its vast deserts.

These three colors sum up the immense diversity of Xinjiang's landscapes. Icy peaks, barren dunes, verdant oases and the extremes of rainfall and temperature can all be found within these 1.6 million square kilometers.

The vast basins in the Xinjiang Uygur Autonomous Region are full of riches. Beneath some lie rich deposits of oil and gas, while others lend themselves to agriculture.

In addition to white, green and yellow, Xinjiang also sports colors that are "painted on" by human activities: black for crude oil and white for cotton. And, in recent years the region has seen a red "invasion" of tomatoes, chili peppers, safflowers, Chinese wolfberries (gouqi) and Chinese red dates.

Why is Xinjiang so suited for these crimson crops? The answer lies in its unique climate and geography.

According to researcher Xu Qinghui from the Xinjiang Academy of Agricultural Sciences, most of the world's tomatoes, chilies and other "red crops" are found around 40 degrees north and south of the equator. That's because these latitudes generally get less precipitation and there's a substantial temperature difference between night and day. The climate, with its hot summer and plentiful sunshine, is perfect for these crops.

It's the summer of 2009, and I'm visiting a state-run farm near Bosten Lake, a large freshwater lake. Under the clear blue skies, rows of poplars are neatly planted in a grid as a wind barrier. Sheltered by the poplars are square, irrigated plots of tomatoes. The seedlings sprouted more than a month ago, and tiny yellow flowers have just emerged.

Red agate

It was only a few decades ago that the tomato came to Xinjiang where it flourished because of fertile soil, abundant sun and a big diurnal temperature range.

Every day in June, plants are treated to 14 hours of continuous sunlight, as well as a temperature difference of well over 15 degrees Celsius - a potent mix almost impossible to find elsewhere in China.

But the soil is fertile only with irrigation - otherwise, very little would grow in the extremely arid region. New drip cultivation has revolutionized cultivation of tomatoes in this water scarce region. "We mix the right amount of nutrients in the water, then carefully control the flow of this solution to the plants," says Zhang Jianfeng, head of the agricultural bureau in Hoxud County. "This way we irrigate and fertilize at the same time."

The system provides just enough life-giving fluid for the tomatoes to thrive, but not weeds, which means less work for farmers. The automated process also means less manpower is needed - only two workers for a four-hectare farm, says Zhang.

According to the Xinjiang Bureau of Statistics, Xinjiang is China's largest producer of tomatoes, with 80,000 hectares cultivated in 2008. That year, around a dozen tomato-processing factories in Xinjiang purchased more than 400 tons of tomatoes worth 1.5 billion yuan (US$220 million) from farmers.

If Xinjiang's annual tomato output was distributed equally among its population of 20 million, each person would receive 275 kilograms.

Most Xinjiang tomatoes are processing tomatoes, also known as paste tomatoes. These have the same taste and texture as ordinary tomatoes, but with a much tougher skin so they can be transported long distances and stored for long periods without spoiling.

"Some of these processing tomatoes are as tough as an inflated ball - you can throw them to the ground and they bounce back even higher," says Liu Zhendong, a senior executive with COFCO Tunhe (a listed company under the state-owned China National Cereals, Oils and Foodstuffs Corp).

Xinjiang produces more than 10 varieties of processing tomatoes with different levels of sweetness and viscosity.

The toughest is Tunhe 41, a bright red, oval tomato that can withstand as much as 6.9 kilograms of force.

Ketchup king

Xinjiang was already Asia's top ketchup producer more than a decade ago; COFCO Tunhe is Asia's largest ketchup maker. Every year it uses more than 3 million tons of tomatoes, and exports 550,000 tons of ketchup and 53,000 tons of processed tomato products to more than 80 countries.

Tomatoes are famously rich in the antioxidant lycopene, as well as carotene, vitamins A, C, B1, calcium, phosphorus, potassium, magnesium and other nutrients.

However, most processed tomato products are destined for Europe and America rather than the domestic market. One reason is that many Westerners use ketchup daily and recognize the tomato's health benefits, while most Chinese regard the tomato only as a common vegetable.

"We produce many tomato beverages, but they do not sell well in China," says Liu, who doubts consumer preference will change soon.

The tomato spread from the forests of South America and came to China by sea in the late Ming Dynasty (1368-1644). It was first grown as an ornamental plant. It was not until the early 20th century that the Chinese used it as food.

Today one in every four tomatoes worldwide is produced in China - the world's largest producer at more than 33 million tons annually - and over half of these are from Xinjiang.

Hot chili

After the peak of summer, oceans of red run along the desert highways for tens of kilometers at a stretch. These beds of chili, each around the size of a football field, are common along National Highway 314 between Hoxud and Yanqi counties, as well as the highway between Urumqi and Kuytun.

The basins are a natural drying yard because of the relative humidity less than 30 percent, surface temperatures exceeding 70 degrees Celsius and strong, searing winds. Chilies can be dried in half a day, after which they are sent to factories or stored at home to be enjoyed during the long winter.

Chilies are a mainstay in regional cooking. A favorite is a fiery dish of chicken, potatoes and chili. Locals prefer dried chilies to fresh ones - they crush pods, add salt and fry the mixture in vegetable oil to make a condiment eaten with dumplings, buns and noodles.

Like the tomato, the chili arrived in China by sea in the late Ming Dynasty. The native crop of Latin America was first cultivated in Chinese gardens as an ornamental plant.

Xinjiang has been growing chili commercially for close to 50 years. According to the Xinjiang Agricultural Department, Xinjiang grew more than 25,000 hectares of chilies in 2008 (these chilies were not consumed fresh, but processed into dried chilies, chili sauce, chili oil and other products), in addition to 770,000 tons of fresh chilies in the same year.

Xinjiang currently produces more than half of all dried chilies in China.