Study On The Characteristics Of Utilization Of Soil Nitrogen For Apple Trees

The situation of 374 apple orchards was investigated in main apple production area of Shan Dong province during 2006²008, those orchards were sampled and the relationship of available nutrients and yield was analysis. The plentiful and stable yield orchard and unstable orchard were sampled at different key phenophase. The nutrition of soil and leaves for different key phenophases were analysis. The characteristics of absorption, utilization and distribution of ¹⁵N-labelled urea and the utilization, residue, loss and transport dynamics of nitrogen on orchard via soil in early spring by seven-year-old'Gala'apple trees (Malus domestica)/Malus hupehensis were studied. The main results were followed:1. The results showed that most orchards were small in Shan Dong province. The characteristics of orchards were small area, thin soil, insufficient quantity of organic fertilizer invested, fertilization for farmer followed experience and proportional imbalance of nitrogen, phosphorus and potassium.2. The nutrition status of soil for main apple production area of Shan Dong province was analysis. The result showed that when the ammonium nitrogen, available phosphorus and available potassium respectively reach 21.06 mg·kg-1, 34.57 mg·kg-1, and 334.30 mg·kg-1, the yield respectively reach to 54016 kg·hm-2, 54328.72 kg·hm-2, 68053.3kg·hm-2. The correlation coefficient between nutrition and yield respectively reach to 0.36, 0.11 and 0.59. The effect of potassium was greatest for yield, nitrogen followed and phosphorus was smallest.3. Dynamics of leaves and soil of high-yield orchard and fluctuating-yield orchard were studied. The result showed that total nitrogen of leaves of two types of tree decreased rapidly, and then decreased slowly, and then decreased rapidly again. Total nitrogen of leaves was highest at sprouting period and lowest after harvest. The stage decreased slowly of high-yield orchard was longer than fluctuating-yield orchard, and decreased rapidly after harvest. Total nitrogen of leaves of fluctuating-yield orchard decreased rapidly at first fruit rapid-swelling stage. Dynamics of total phosphorus was the same with total nitrogen, and total phosphorus of high-yield tree was higher than fluctuating- yield tree. Total potassium of two types of tree was a downward trend in annual cycle, and total potassium of fluctuating-yield tree violent changes. Ammonium nitrogen of two type orchards decreased firstly, and then increased. It was highest at sprouting period and lowest at first fruit rapid- swelling stage. Available phosphorus increased in annual cycle, and available phosphorus of fluctuating-yield orchard violent changes. Available potassium increased in annual cycle, and available potassium of high-yield orchard was higher than fluctuating-yield orchard.4. The characteristics of absorption, utilization and distribution of ¹⁵N-labelled urea via soil in early spring by seven-year-old'Gala'apple trees (Malus domestica)/Malus hupehensis were studied. The results showed that, at full-bloom stage, the Ndff of fine root was the highest, thick root followed. During shoot rapid-growing period and fruit rapid-expanding stage, the Ndff of new organs was higher than storage organs. After fruit harvest, the Ndff of thick root and fine root was higher than that of storage organ up-ground, and new organs lowest, ¹⁵N absorbed by trees was transferred to storage organs. The characteristics of ¹⁵N distribution were differential in different phenophase. At full-bloom stage, ¹⁵N absorbed by trees was firstly distributed to roots. At shoot rapid-growing stage and fruit rapid-expanding stage, ¹⁵N distribution ratio of roots decreased continuously, and ¹⁵N absorbed in trees was firstly distributed to new organs. At fruit maturity stage, fruit organs became the new growing center. After fruit harvest, ¹⁵N absorbed in trees was transferred back to storage organs. ¹⁵N absorbed was transported to the growing center preferentially. The utilization ratio of N fertilizer was improved gradually with the process of phenophase. After fruit harvest, the utilization ratio is 27.54%. 5. The utilization, residue, loss and transport dynamics of nitrogen on orchard via soil in early spring by seven-year-old'Gala'apple trees (Malus domestica)/Malus hupehensis were studied, using tracer technique of ¹⁵N. The results showed that the utilization ratio of nitrogen fertilizer was low at every period. At full-bloom stage, the utilization ratio of nitrogen fertilizer was lowest (11.38%). the utilization ratio of nitrogen fertilizer was improved gradually with the process of phenophase. After fruit harvest, the utilization ratio of nitrogen fertilizer was highest (27.54%). At full-bloom stage, the residue rate of nitrogen fertilizer was highest (57.10%). the residue rate of nitrogen fertilizer was decreased gradually with the process of phenophase, and after fruit harvest, the residue rate of nitrogen fertilizer was lowest (16.47%). At full-bloom stage, the residue rate of nitrogen fertilizer of 20～40cm layer was highest and, after fruit harvest, it was lowest. At the new shoot growth stage, the residue rate of nitrogen fertilizer (0～20cm layer) was highest and, at fruit maturity stage, it was lowest. However, the residue rate of nitrogen fertilizer (40～60cm layer) was up to highest at fruit rapid-swelling stage. After fruit harvest, the residue rate of nitrogen fertilizer (0～20cm layer) was higher than at fruit maturity stage and the residue rate of nitrogen fertilizer(other layers) was lowest. On the contrary, the loss rate of nitrogen fertilizer was improved gradually with the process of phenophase. At full-bloom stage, it was lowest to 31.53% and, after harvest, the tiptop was 58.40%. The content of ¹⁵N in different soil layer in soil profile has significant differences.