Soil Fertility In Orchards And Plant Nutrition And Fertilization Of Torreya Grandis Merrillii

Torreya grandis'Merrillii'is a high-valued rare tree species. The kernel of the Torreya grandis'Merrillii'nuts is a reputed healthy food in China. A 3-year longterm field soil mornitoring was carried out to examine soil fertility and nut yield of Torreya grandis'Merrillii'orchards in Shengzhou city, a key main area for this tree growth and its nut production in China. Soil and plant samples were collected periodically. Soil analysis showed that soil pH (3.8-6.1), soil organic matter content (SOM) (19.4-167.7 g·kg^-1), and soil available nitrogen (N) (48.3-445.6 mg·kg^-1), phosphorus (P) (1.5-483.6 mg·kg^-1) and potassium (K) (32.8^-1565.0 mg·kg^-1) varied greatly between different orchards and growth seasons, with mean values of pH 4.9, SOM 53.8 g·kg^-1, N 192.6 mg·kg^-1, P 169.2 mg·kg^-1 and K 352.8 mg·kg^-1, respectively, during the 3-year mornitoring. These results indicated that most of the orchards were rich in soil available N, P and K. Nutrient concentrations of NPK in plant foliage changed greatly with growth stages, being highest in June and decreased thereafter.A field N fertilizer experiment showed that growth of tree seedlings of Torreya grandis'Merrillii'was affected remarkably by urea application. Plant growth increased with urea application from 0 to 60 kg·ha^-1. By contrast, the growth decreased while more urea was supplied. The first application of N in spring was advised in the range of 47-60 kg·ha^-1 of urea for optimal seedling growth.The field experiments of B, Zn and K fertilizer application showed that the growth of Torreya grandis'Merrillii'seedlings was improved by application of either individually or in combination of B, Zn and K. The application of B was most effective among these 3 nutrients. But, the extensiveness of plant growth responses to them were not as great as to N. Nutrient concentrations of B, Zn and K in the foliage of Torreya grandis'Merrillii'were not significantly different between different treatments. Concentrations of B, Zn and K in foliage were high compared with the other common plant species, especially B, indicating high demand of these nutrients for growth of Torreya grandis'Merrillii'.Overall it was revealed that the Torreya grandis'Merrillii'orchards with over-dosages of NPK fertilizers were common. The application of micronutrients such as B and Zn needs to be encouraged. There is an urgent need to optimize soil management and fertilization to improve soil conditions and so that to maintain sustainable production of the Torreya grandis'Merrillii'orchards.