The Selection Of Ziziphus Jujuba Cv. Daguazao And Its Response To NPK Balanced Fertilization

Jujube is one kind of the native fruit in China. Breeding and balance fertilizing were important aspects of jujube research. Cultivar selection work of jujube was conducted, a good cultivar 'Dagua' jujube was obtained, its fruit is big and can be fresh-eating. Its growth and development character were observed. Experiments on the level and ratio of nitrogen, phosphate and potassium in pot were conducted to investigate the effects of their different ratios and levels on the tree growth, fruit bearing and quality of 'Dagua' jujube. The main results are as follows.1 Selection of 'Dagua' jujube, its growth and development character1.1 Selection of 'Dagua' jujube'Dagua' jujube was found in Linhedian town, Dongming county, Shandong province when jujube germplasm was investigated in 1982. It was introduced and grafted on the jujube tree in the nursery of Shandong Institute of Pomology in 1983. Observation results showed that its fruit is big and very uniform in size, it bears fruit early and has good harvest, fruit quality is best, it is a good cultivar for extension. It was approved as a cultivar by Shandong Inspection Commision of Agricultural Crop Cultivars in 1998.1.2 Growth and development character'Dagua' jujube is a rare cultivar that is suitable for fresh-eating. Its fruit is very big and uniform in size, average fruit weight 25.7g and maximum fruit weight 50g. It has thin peel, smooth, light red or brown skin. Its fruit flesh is fragile, contains much more juice and 32~34% soluble solids, fruit quality is best.'Dagua' jujube bears fruit early. After jujube scion was grafted on stock in the nursery, about 40% plants had fruit, a plant had 40 fruit at maximum in the first year. All plants had fruit and a tree could bear 1~1.5kg fruit in the second year, 15~20kg fruit in the fifth year. When 'Dagua' jujube is cultivated in the inland of Shandong province, its buds sprout in medium April, full blossom period is from late May to early June, fruit were harvested in early or medium September, its fruit growth period is 90~95 days. The tree is big, its height is 7.0 m and diameter 5.2 m, branch length 65.0~94.0 cm, shoot length 10.0~18.0 cm with 11.8 leaves.'Dagua' jujube has strong adaptability, it can be cultivated in the region of many climate and soil conditions. It grows very well and has a stable output in different kinds of soils such as sandy and clay land in plain and mountainous regions.2 Trial on the level and ratio of nitrogen, phosphate and potassium2.1 When nitrogen(N), phosphate(P) and potassium(K) ratio was 2:1:2,tree grew very well and had appropriate bearing shoots, fruit-bearing rate was 1.71% and a tree could bear 7.28kg fruit in the fourth year, fruit total sugar content was 29.58%, fruit quality was best. This ratio should be optimum fertilization ratio.2.2 When nitrogen(N), phosphate(P) and potassium(K) ratio was 2:1.5:3, the tree had a height of 411 cm, its trunk diameter is 8.47 cm, with 7.83 developing shoots and 100.14 buds, fruit-bearing rate was 1.05% and a tree could bear 5.01kg fruit, fruit total sugar content was 29.8%, fruit quality was improved. This ratio can be reference fertilization ratio.2.3 When nitrogen(N), phosphate(P) and potassium(K) ratio was one of the ratios 0.5:1:2, 1:0.5:2,1:1:1,1:1.5:2,1:1:3 or no fertilizer was used, the tree only developed 2.47 shoots and 53.69 buds, fruit-bearing rate was 0.4% and a tree only produced 1.81kg fruit, fruit total sugar content was 27.45%, fruit quality was not good. These ratios are not recommended. But one thing need to be mentioned, when 1:1:3 (high potassium content) ratio was used, fruit total sugar content reached up to 31.78%, fruit quality was greatedly improved. It indicated that potassium can improve fruit quality.2.4 When complete inorganic fertilizer was used and half amount of organic fertilizer was used, there is much difference in fruit quality. When half amount of organic fertilizer was used, fruit quality was improved, the contents of soluble solids, total sugar, titratable acidity and Vc incresed 4.1%, 4.2%, 0.06, 39.35%, respectively. Therefore, it is recommended to use more organic fertilizer in fruit production.