Effects of biochar and nitrogen fertilizer application on soil fertility and jujube yield and quality

ObjectivesA three years’ consecutive field experiment was carried out to study effect of application of different biochar and nitrogen fertilizer on soil fertility, jujube yield and quality in jujube orchards of the North China Plain in order to provide a scientific basis for high-efficient fertilization and sustainable development in jujube orchards.

MethodsField experiments were conducted from 2013–2015 in the Academy of Forestry Science of Puyang, Henan Province. A widely planted jujube cultivar in Henan Province was chosen and trees of fifteen-year-old were used as tested materials in this study. There were total of thirteen treatments, including CK (no fertilizer), four-level of biochar (C 0, 2.5, 5 and 10 t/hm², namely, C₀, C₁, C₂ and C₃) and three-level of nitrogen fertilizer (N 300, 450 and 600 kg/hm², namely, N₁, N₂ and N₃). At the end of September 2015, fresh jujube, and 0–20 cm surface soil samples were collected, and soil fertility, jujube yield and quality were investigated.

Results1) Compared with the control, the highest total nitrogen and available phosphorus contents was in the C₃N₃ treatment with increment of 80.3% and 32.8%, respectively; the highest total potassium and phosphorus contents were observed in the C₃N₁ treatment with increment of 55.3% and 27.9%, respectively; and the highest available nitrogen and potassium contents were observed in the C₃N₂ treatment with increment of 68.0% and 41.0%, respectively; the lowest soil bulk density (1.22 g/cm³) was observed in the C₃N₃ treatment with decrease of 15.9%. 2) The contents of total sugar, vitamin C, soluble solid, protein and amino acid of the jubilee fruits in the fertilization treatments were generally higher than in the control, but only amino acid content was increased significantly (P < 0.05), with the greatest increment of 100% in C₃N₁ treatment. 3) The yields of jujube in different fertilization treatments were increased by 4.5%–26.9% compared to the control, with the greatest value in the C₃N₁ treatment.

ConclusionsThe combined application of biochar and nitrogen fertilizer plays an active role in increasing jujube yield and improving soil nutrient uptake, soil fertility. Biochar contributes both in reducing the input of the chemical fertilizer and improving soil fertility. The optimal amounts for biochar and nitrogen fertilizers according to the yield should be 10 t/hm² and 300 kg/hm², respectively.