Cucurbit Genetics Cooperative Report 18:1-2 (article 1) 1995
Meng Zhang, Hongwen Cui and Jiangui Li
Department of Horticulture, Northwestern Agricultural University, Yuangling Shaanxi, 71200, P.R. China
The basin of the “Three Rivers” (the Yaluzangbu, Lhasa and Nyanchu rivers) is situated in the mid-south region of Tibet. It is the center of politics, economics, culture and commerce in Tibet. Eighteen cities and countries of the Lhase, Xigaze and Shannan districts belong to this area, which rises to elevation of 3600 to 4100 meters. The authors participated in the “Three Rivers Project” for comprehensive agricultural harnessing in 1994. The conditions of production, introduction of cucurbit crops and climate in this area are documented here.
The climatic characteristics of agricultural lands are governed by the terrain (a plateau) and geographical position (Table 1).
- The air is thin and the oxygen content is between 62.0-65.4% of that found in the plain area. The atmospheric pressure is 600 mbar, and CO2 content is less than half that found at sea level.
- The solar radiation is intense, the annual light period is about 3000 hr.
- The ultraviolet rays are abundant, the absolute quantity of the UV rays whose wavelengths are less than 400 mum is 2.3 times that of sea level. Some pathogens survive in these environments, but only with difficulty.
- The temperature is much lower than that found in Yangtze River valley which is at the same latitude. The effective accumulate temperature of the most regions is less than 800 C.
- The line of demarcation between dry and moist seasons is very clear. This transition zone is often the site of high winds, low temperature and low rainfall from October to April. About 90% of the precipitation falls between May and September. Rains usually occur at night.
Because of such climatic conditions, the cucurbit crops cannot grow outdoors except custard squash (Cucurbita pepo L.) which survives at some lower elevations. In the lower basin regions of this area, cucumber canopies can mature but fruit formation is difficult. However, environments which are adequately protected can take advantage of the short growing season, large range in day temperatures, and abundant sunshine. Most cucurbit crops can be culture under protective environments in this basin. Due to naturally occurring strong winds, the primary plant protection in this region is provided by glasshouse structures.
The production of cucurbit crops started in the late 1950’s and expanded gradually in the 1980’s. Because great efforts were given by the central authorities and local governments to develop the vegetable-basket-project, several millions Yuan Reminbi were put into developing the vegetable protective ground in the Lhasa, Xigaze and Zedong provinces in recent years. There are about 25-30 ha of cucurbit production in these regions. Cultured cucurbits include cucumber (Cucumis sativus L.), custard squash (Cucurbita pepo L.), pumpkin (Cucurbita moschata L.), watermelon (Citrullus lanatus L.), wax gourd (Benincasa hispida Cogn.), balsam pear (Momordica charantia L.), sponge gourd (Luffa aegyptiaca Roem), and bottle gourd (Lagenaria siceraria Standle). The areas devoted to cucumber (50%) and squash (30%) production play an important role during the entire year.
Double covered plastic is used in the production of cucumber and squash during the winter. Large plastic shelters can be used during April to October. If a harvest is desired earlier than spring, then small, covered shelters under large shelters can be employed. Squash can be cultured outdoors in the Zedong and Lhasa regions. Crops are usually sown in the middle of May and harvested from July to September. Later maturing fruits can be stored and sold during winter and subsequent spring. The areas of watermelon culture in the Lhasa region are smaller by comparison. Watermelons are mainly planted under large plastic shelters in spring (the last ten days of April). Small shelters can be used to increase growing temperatures. The production of other cucurbit crops in this region is comparatively small.
The cucurbit breeding programs are confined to introducing varieties from other districts. The varieties of cucumber cultured in this area include: ‘Changchun Mici’, ‘Beijing Davi’, ‘Nongda No. 14’, ‘Zongnong No. 19’, ‘Nongcheng No. 3’, ‘Jinyan No. 6’ and ‘Jinza No. 2’. Yield averages between 6.0 x 104 kg per ha. The varieties of squash include: ‘Yiwohou’, Beijing Duanman’, and ‘Zaoquing Yidai’. Yield averages between 4.5 x 104 kg to 6.0 x 104 kg per ha. The varieties of watermelon include: ‘Sumi No. 1’, ‘Zongyu No. 4’, ‘Jiali’, ‘Taiwan Xinhongbao’ and ‘Xinliubao’. Yield averages are about 3.75 x 104 kg per ha. However, yields of 5.7 x 104 kg per ha have been recorded.
Since the history of cucurbit cultivation in Tibet is short, technologies for crop cultivation have not been popularized and thus production has been low. No agricultural chemicals have been used because of the low incidence of disease. Thus, fruits do not contain agricultural residues. As more varieties are introduced and pathogen inoculum load increases, more diseases will occur. Diseases which are predictable include: Sclerotinia rot (Sclerotinia sclerotiorum (Lib) (de Bary) angular leaf spot (Pseudomonas lachrymans Carsn), powdery mildew (Sphaerotheca fuliginea Poll), and leaf spot (Cercospora citrullina Cooke). Fusarium wilt (Fusarium oxysporum f. sp. niveum Snyder) and anthracnose (Colletotrichum orbiculare Arx) have been found to reduce watermelon production. Attention is not paid to all of these diseases. The low numbers of butterflies and bees necessitates hand-pollination which significantly increases production costs. This is true of most crops except cucumber.
Table 1. Sunlight heat energy and water resources in the basin of the “Three Rivers” of China
Regions |
Annual free-frost period (days) |
Annual average temp (C) |
Cumulative temp (C) |
10C soil average temp |
Average rainfall (mm) |
Annual sunshine time (hrs) |
Annual solar radiation (kcal/cm2) |
| Lhasa | 138 | 7.5 | 2116.9 | 10.3 | 4444.8 | 3007.7 | 191 |
| Mezhugongka | 91 | 5.4 | 1547.7 | 8.9 | 542.1 | 2813.1 | — |
| Nimu | 91 | 6.8 | 1801.6 | 10.7 | 324.2 | 2947.4 | 180.8 |
| Zedong | 143 | 8.2 | 2262.8 | 12.0 | 408.2 | 2938.0 | 178.9 |
| Xigaze | 122 | 6.3 | 1821.4 | 10.5 | 431.2 | 3240.3 | 192.4 |
| Gyangze | 113 | 4.8 | 1098.4 | 8.6 | 304.2 | 3189.8 | 188.4 |
Literature Cited
- Shunkai Li. 1992. Vegetable cultural technology of Tibet, Chinese agricultural science and technology publishing house.
- Agricultural bureau of Tibet autonomous region. 1987. Practical agricultural technology of Tibet. Tibet people’s publishing house.
- Huaxin Xu. 1992. Tibet autonomous region geography Tibet people’s publishing house.