Effects of fertilizing on seasonal variation of soil mites in farmland

The seasonal variations of soil mites are studied in farmland of experiment station of China Agricultural University, Quzhou County, Hebei Province. The results show that the numbers of soil mites vary with seasons and the peaks of variation appear in May and from August to September. Fluctuation of number in the plots using organic fertilizer changes less than in the plots using chemica l fertilizer during the year. Mesostigmata mites are found in the plots using chemical fertilizer after July.