Abstract: This paper reports the research results of fertilization of the grated seed orchard of Chinese fir (Cunninghamia lanceolata Hook.) in Dongan, Hunan province. The results revealed that it was the best plan for fertilization to improve the production of conelets that each tree was spreaded 0.2kg ofpotassium chloride, 0.4kg of urea and 0.3kg of superphosphate in every middle 10 days of March, June and August. The seed quality by fertilization was not obviously effected. Analyses of nutrient elements in needles and soil showed the reason why the seed production was so low in the orchard was that Mn content was too high and B content was deficient. It was suggested that lime should be added to the soil and B be spraied on the foliage, and the mostsuitable period for spreading N, P, K fertilizers was from March to August in a year. The desirable period of collecting leaf samples for nurtientdiagnosis was August. It was found that the critical values of different nutrient elements in the needles were N 0.8%, P 0.2%,K 0.7% with the suitable ranges N 0.8-1.2%, K 0.7-0.9%. Ploughing and weeding could not significantly improve seed production of the orchard.

Key words: Chinese fir, Seed orchard, Yield, Nutrient element, Fertilization