of silver, bronze, tin, and lead increased to 3, 23, 54, and 49 times that of Tang levels. Officially registered Salt production also rose at least 57%. The government regulated several other industries. Sulphur, an ingredient in gunpowder – a crucial new weapon introduced during the Tang – became a growth industry, and in 1076 was placed under government control. In Sichuan province, revenue from the Song government's monopoly on tea was used to purchase horses for the Song's cavalry forces. Chancellor Wang Anshi instated monopolies in several industries, sparking controversy. In order to supply the boom in the iron and other industries, the output of mines increased massively. Near Bianjing, the Song capital, according to one estimate over one million households were using coal for heating, an indication of the magnitude of coal use. Light industries also began to prosper during the Song, including porcelainwhich replaced potteryshipbuilding and textiles. Compared with the Tang, textile production increased 55%. The historian Xie Qia estimates that over 100,000 households were working in textile production by Song times, an indicator of the magnitude of the Song textile industry. The urbanisation rate of the Song increased to 12%, compared with 10% during the Tang. Song agriculture Agriculture advanced greatly under the Song. The Song government started a series of irrigation projects that increased cultivatable land, and encouraged peasants to cultivate more land. The total area of cultivated land was greatly increased to 720 million mou, a figure unsurpassed by later dynasties. A variety of crops were cultivated, unlike the monocultures of previous dynasties. Specialised crops like oranges and sugar cane were regularly planted alongside rice. Unlike the earlier self-sufficient peasantry of the Han and Tang eras, rural families produced a surplus which could be sold. The income allowed families to afford not only food, but charcoal, tea, oil, and wine. Many Song peasants supplemented their incomes with handicraft work. New tools, like the Water Wheel, greatly enhanced productivity. Although most peasants in China were still primarily rice farmers, some farmers specialised in certain crops. For example, Luoyang was known for its flower cultivation; flower prices reached such exorbitant prices that one bulb reached the price of 10,000 coins. An important new crop introduced during the Song was Champa rice, a new breed which had superior yields to earlier forms of rice and greatly increased rice production. The practice of multiple cropping, which increased yields