THE Guangdong treasury has swollen dramatically but local officials are complaining about insufficient investment in education and other welfare benefits. Officials of China's richest province are also eager that Beijing will keep its promise that the ''experimental zone'' can keep the bulk of its revenue for re-development. On the fourth day of the Guangdong People's Conference, economics officials revealed that the province's income for 1992 had increased substantially mainly due to economic activities spurred by the visit of patriarch Mr Deng Xiaoping early that year. Preliminary statistics show that total revenue last year amounted to 22.136 billion yuan (HK$29.64 billion), an increase of 17.48 per cent compared with the original estimate, and an increase of 35.25 per cent compared with 1991. In his budget report yesterday, Director of the Finance Department Mr Zeng Bingsheng said enhanced industrial production and a surge in foreign investment contributed 3.177 billion yuan, or 71 per cent of the total increase in the province's revenue. New sources of tax revenues, such as stamp duties, land sales and transaction of stocks, were incorporated into government budget calculations for the first time. Total expenditure last year amounted to 21.999 billion yuan, 37.21 per cent more than the original estimate and 31.92 per cent higher than 1991. Especially prominent was Shenzhen, which saw a 72.81 per cent increase of expenditure over 1991, totalling 4.2 billion yuan. The finance chief attributed the significant jump in expenditure last year to increased investment in infrastructural projects, including energy, transport, and basic urban facilities. However, the relaxation on price control, especially on the price of rice, helped Guangdong save a total of 403 million yuan. Mr Zeng disclosed that Guangdong's contribution to central coffers had increased by 19 per cent a year since 1988. He said over the past five years, his province had contributed 77.417 billion yuan. Mr Zeng warned that some localities had exceeded their powers in approving reductions or exemption of tax. Senior officials admitted that in spite of the general wealth, some poor local administrations had difficulty financing basic projects. Also, additions to the education budget had been used to adjust salaries and subsidies of employees, leaving little for quality improvement. In his projections for 1993, Mr Zeng predicted revenue would reach 23.471 billion yuan, up by 6.03 per cent from 1992, while expenditure would be adjusted to match revenue in order to create a balanced budget. Bowing to Beijing's warnings against overheating the economy, Guangdong has decided that spending on infrastructure building this year will remain at the 1992 level of 3.088 billion yuan.