Abstract: 【Objective】Watermelon is one of the main cash crops in the semi-arid regions of Loess Plateau and its planting area has been expanding steadily in recent years. However, due to insufficient precipitation and its uneven temporal and spatial distribution, watermelonoften suffers from water stress and waterlogging, resulting in yield reduction. The objectives of this study were to explore rainfall-collection and high-yield cultivation techniques in order to improve soil moisture-thermal conditions by plastic film mulching.【Method】The experiment was implemented in Taichang Township of Ning County, Gansu Province in 2011-2013 with the aim to identify the effects of different cultivation methods on soil water, soil temperature and yield. The trial was a random block design with 3 replications, and 5 treatments which included sowing on beds with full plastic film mulching (RM), furrow sowing on beds with full plastic film mulching (GM), sowing in furrows with full plastic film mulching (TG), furrow sowing on beds with half plastic film mulching (GH), sowing on beds with half plastic film mulching (RH). The bed width was 100 cm with furrow width 30 cm. For GM and GH treatments the width of furrow on top of bed was 20 cm and the depth was 10 cm. Soil moisture in 0-100 cm profile was measured by drying method. Soil temperature was checked by Stow Away Tidbit Temp Logger at the soil layers of 5 cm, 10 cm and 15 cm. The planting density in each treatment was 7 692 plants/hm².【Result】Soil moisture was affected by collected rainfall and stage of watermelon growth. Compared to RH, soil water contents of TG, GM and GH in 0-10 cm increased by 41.41%, 37.82 and 32.69% at seedling stage, TG, RM and GH in 0-40 cm increased by 13.91%, 10.61% and 6.75% at extension stage, GM and GH in 0-40 cm increased by 8.50% and 5.49% at fruiting stage and GM, GH, TG and RM in 0-40 cm increased by 10.51%, 10.33%, 4.98% and 3.66% at maturing stage, respectively. The sequence of soil water storage was as GH＞GM＞TG＞RM＞RH at fruiting stage. The daily variation of soil temperature changed as ‘S’ type negative sine curve, the amplitude decreased, the phase shifted backwards and the cycle extended with soil depth deepened. The sequence of average daily soil temperature was as RM＞RH＞GM＞TG＞GH. The time of maximum and minimum daily soil temperature was delayed 1 h as soil depth deepened every 5 cm. Soil temperature of the beds was higher than that of furrow and soil temperature of RM was the highest among all treatments. The sequence of soil temperature increase was as GM＞TG＞GH＞RH＞RM. The yield of GM in 2012-2013 was the highest and increased by 10.34% and the yield of GH in 2011-2013 increased by 7.66% compared to RH. The sequence of yield increase was as GM＞GH＞RM＞TG. The function of rainwater collection and yield increase of GM and GH were significantly improved.【Conclusion】The effects of rainfall collection, soil temperature increase and watermelon yield improvement were verified by 3-year study. GM and GH can collect more rainfall, increase soil temperature and promote yield. Application of the techniques can effectively improve the rainfall utilization and achieve stable and higher yields. It can also be used as a highly effective cultivation solution for watermelon production in dryland areas on the Loess Plateau.

Key words: watermelon, semi-arid area;  plastic film mulching methods, yield;