This area has a semi-tropical
monsoon climate with annual sunlight of 1800–2037 h, a frost-free
period of about 235–322 days, mean precipitation of 1632 mm,
annual mean temperature of 16.6–17.5 C, July mean temperature
of 26.6–28.5 C and January mean temperature of 5.0–6.9 C. Prior
to the present study, traditional clean tillage (frequently tilling soil
to remove all weeds) had been always applied in these citrus
orchards.