However, due to hilly terrain and forest cover, only 27 per cent of the land is available for cultivation. Rice, the major crop of the state, is cultivated in 91 per cent of the cropped area. According to the Directorate of Economics & Statistics, Government of Tripura, in 2009–10, potato, sugarcane, mesta, pulses and jute were the other major crops cultivated in the state. Jackfruit and pineapple top the list of horticultural products. Traditionally, most of the indigenous population practised "jhum" method (a type of slash-and-burn) of cultivation. The number of people dependent on "jhum" has declined over the years. Pisciculture has made significant advances in the state. At the end of 2009–10, the state produced a surplus of 104.3 million fish seeds, primarily carp. Rubber and tea are the important cash crops of the state. Tripura ranks second to Kerala in the production of natural rubber in the country. The state is known for its handicraft, particularly hand-woven cotton fabric, wood carvings, and bamboo products. High quality timber including sal, garjan, teak and gamar are found abundantly in the forests of Tripura. Tata Trusts signed a pact with Government of Tripura in July 2015 to improve fisheries and dairy in the state. The industrial sector of the state continues to be highly underdeveloped – brickfields and tea industry are the only two organised sectors. Tripura has considerable reservoirs of natural gas. According to estimates by Oil and Natural Gas Corporation (ONGC), the state has 400 billion metres3 reserves of natural gas, with 16 billion metres3 is recoverable. ONGC produced 480 million metres3 natural gas in the state, in 2006–07. In 2011 and 2013, new large discoveries of natural gas were announced by ONGC. Tourism industry in the state is growing – the revenue earned in tourism sector crossed for the first time in 2009–10, and surpassed in 2010–11. Although Bangladesh is in a trade deficit with India, its export to Tripura is significantly more than import from the state; a report in the newspaper "The Hindu" estimated Bangladesh exported commodities valued at about to the state in 2012, as opposed to "very small quantity" of import. Alongside legal international trade, unofficial and informal cross-border trade is rampant. In a research paper published by the Institute of Developing Economies in 2004, the dependence of Tripura's economy on that of Bangladesh was emphasised.