| Lanzhou gravel-mulched fields in northwest China is arid and semi-arid area unique and traditional drought-relief form of farming, which is one of the soil cover systems. The extremely dry weather conditions and low temperatures in early spring of gravel-mulched fields zone are serious threats to watermelon production .The gravel-mulched fields have a better effect on increasing soil temperature and storing water than the average farmland, but it still can't reach the requirement of yield and excellent production. So we should combine the modern agriculture plastic-film mulching technology with traditional gravel-mulched fields,To explore the more obvious mulching pattern of increasing soil temperature and moisture, perfect the watermelon cultivation techniques of drought resistance in gravel-mulched fields, to local rainfall resource utilization efficiently and increase economic benefits, and further enhance the production efficiency of gravel-mulched fields.This test made in 2009 in Gaolan county of Lanzhou, the trail comprised four treatments including only gravel-mulched field (CK),half plastic film and gravel-mulched field (HM),full plastic film and gravel-mulched field(FM),ridge-forming and plastic film mulching(RM). The research contents include soil temperature conditions and the variation of soil moisture conditions and watermelon growing development of several aspects based on different mulching approaches in the gravel-mulched fields,. The aim is to explore the theory that different plastic-film mulching methods on soil water-heating condition and the growing development of watermelon, test results show that:1) Different plastic-film methods showed a similar diurnal variation of soil temperature in 0 to 25 cm vertical soil layer. They all passed in a temperature wave like negative sine curve from the soil surface to the deep, and it would become weaker with the deepening of soil layer. the daily average soil temperature of FM was the highest in all treatments, there were no significant differences between RM and HM, CK is minimum; the average soil temperature and accumulated temperature of different growth period of watermelon each is FM> RM> HM > CK, as a whole watermelon growing period , the total accumulated temperature of FM,RM,HM were more than that of CK by 266.83℃,197.49℃and 172.54℃respectively .2) Except the fruit stage, the soil moisture content of dry gravel-mulched fields was the highest in the 0-20 cm soil layer ,below 20 cm, it decreased with the deepening of soil layer and rose again at about the 100 cm . In the seedling stage and vines stage of watermelon, FM and RM respectively showed a good preservation of soil moisture effects. The soil moisture content of FM and RM increased by 1.5 percentage points than HM and increased by 2 percentage points than CK in the 0-40 cm soil layer; water storage of 1m soil layer of FM,RM,HM were more than that of CK by 6.8㎜,9.4㎜ and 4.6㎜ respectively, the total water consumption of 1m soil layer of 1m soil layer of FM,RM,HM were more less than that of CK by 6.9㎜,9.5㎜ and 4.7㎜ respectively, WUE of yield of FM,RM,HM were more than that of CK by 2.8 times,2.4times and 2.2 times respectively.3) Different approaches of plastic-film mulching also shortened the growth stage of watermelon in varying degrees, in which FM were 10 days earlier than CK and 4 to 5 days earlier than HM. The main vine of FM,RM,HM were more than that of CK by 12.7%,11.5% and 8.8% respectively;LAI of FM,RM,HM were more than that of CK by 67.77%,25.62% and 31.41% respectively;the Chlorophyll content of watermelon leaf of FM,RM,HM were more than that of CK by 4.26%,1.97% and 2.79% respectively.4) Watermelon yield of FM,RM,HM were more than that of CK by 2.5 times,2 times and 1.9 times respectively, center soluble solid content of FM,RM,HM were more than that of CK by 1.12°,0.76°and 0.26°respectively;fringe soluble solid content of FM,RM,HM were more than that of CK by 1.07°,0.67°and 0.33°respectively;soluble total sugar content of FM,RM,HM were more than that of CK by 1.17%,0.68% and 0.38% respectively;Vc content of FM,RM,HM were more than that of CK by 8.14%,19.6% and 5.12% respectively.5) The absorption and utilization of nitrogen, phosphorus and potassium of all plastic-film mulched treatments were higher than the bare gravel-mulched fields. The use ration of nitrogen of FM, RM, HM were more than that of CK by 9.85%,6.58%and5.26% respectively; the use ration of phosphorus of FM, RM, HM were more than that of CK by 3.70%,2.26%and1.91% respectively;. potassium absorption of FM, RM and HM were more than that of CK by 2.52 times,2.09 times and 1.80 times respectively. In addition, the economic benefits of watermelon of FM, RM and HM were more than that of CK by 2.95 times,2.36 times and 2.42 times respectively.In the test, different approaches of plastic film mulching showed better effects than bare gravel-mulched fields in respect of soil temperature,moisture,growth and development of watermelon,FM was the best than other treatments,the cultivational pattern could used efficiently rainfall resource and increased economic benefit of watermelon in gravel-mulched fields.
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