JINAN, Aug. 25 (Xinhua) -- Chinese scientists are encouraging farmers to use controlled release compound fertilizers to curb nutrients runoff and protect the environment in the wake of major algae bloom outbreaks believed mainly to be caused by run-off from heavy fertiliser use.

China is home to only 7 percent of the world's farmland, but its fertilizer consumption accounted for more than 35 percent of the world's total, said Feng Yuanqi, a senior expert on chemistry.

Nitrogen, phosphorus and potassium fertilizers are frequently overused and misused, and a large quantity of fertilizers are lost to leaching and evaporation, said Feng.

Only 30-35 percent of the nitrogen fertilizers applied to farmland played a role in helping crops grow and the ratios were 15-20 percent and no more than 65 percent for phosphorus and potassium fertilizers respectively, according to Shi Yuanliang, who has long been engaged in development of new fertilizers.

Scientists say the effectiveness of phosphorus in conventional compound fertilizers dropped to 80 percent after being applied to soil for 35-40 days.

The runoff of nutrients from chemical fertilizers not only increased the cost of farming and caused waste of resources; it also brought huge pressure for the environmental protection effort.

For nitrogen fertilizers alone, statistics show, as much as 14 million tons of nitrogen, valued at 50 billion yuan (6.6 billion U.S. dollars), are lost to leaching and evaporation every year in China.

Over the past several months, the nutrient runoffs and other pollutants caused blue-green algae to bloom in China's major lakes-- Taihu Lake, Chaohu Lake and the Dianchi Lake, endangering water supply in nearby cities. In July, a reservoir in Changchun City, northeast China, was sullied after the nutrients amassed.

According to a report issued by the Institute of Soil Science under the Chinese Academy of Sciences, fertilizer runoffs accounted for about 59 percent of the pollutants that sullied the Taihu lake, while industrial pollutants only accounted for 10-16 percent.

However, China has to produce enough grain to feed its population of 13 billion, and the key to a greater grain output lies in fertilizers, said 82-year-old Feng.

As it is hard to curb the heavy use of fertilizers, Chinese sciences and agricultural workers have developed fertilizers that are more environment-friendly, including the controlled release fertilizers that allow the nutrients to be released at a slower rate throughout the growing.

The controlled release fertilizers have been put to use in grain bases in the northeastern and eastern parts of China. The fertilizers, which remained effective for 120 days, improved the effectiveness by 30 percent and increased wheat and maize production by 20 percent, said Zhang Yulong, president of the Shenyang Agricultural University, citing a comparative study.

The fertilizers have proven effective on about 2.3 million hectares of cropland, and will be used in other areas of China, Zhang said.

China now has some 40 companies producing controlled release fertilizers, with a combined output of 350,000 tons a year, said Wu Zhijie, a researcher with the Shenyang-based Institute of Applied Ecology under the Chinese Academy of Science.

The fertilizers have a bright future in the China market because the government also encourages development and production of more environment-friendly fertilizers and related applied technologies, Wu added.