Suitable bunch pieces and planting density saving water and increasing yield of potato with black plastic film mulching and ridge planting in dryland

Abstract: In order to improve the efficiency of agricultural machinery and agronomic integration and crop water use efficient in dryland, 4 years of split-plot experiments were carried out in at Dry Farming Experimental Base in Zhuanglang County of Gansu Province from 2013 to 2016. According to precipitation from 1989 to 2016, the years of 2013, 2014, 2015 and 2016 belonged to humid, dry, normal and dry years, respectively. Three treatments were designed including different plastic film colors, bunch pieces and planting density. The plastic film included white and black colors. The bunch pieces included 1 and 2 pieces before the year of 2015 and whole piece was added in 2016. The planting density included 72 720 (row spacing of 25 cm), 51 945 (row spacing of 35 cm) and 40 395 plants/hm2 (row spacing of 45 cm). The potato was cultivated on ridges. During the potato cultivation, the irrigation was not performed. The results showed that the growth period was shorter for the dry year but expanded for the humid year. The plastic film color could significantly affect potato yield. On average, the yield was increased by 8.1% when the black film was used. However, in the dry year, the yield was not significantly different. The influence of plastic film color on the yield was greater in the humid year, followed by the normal year and the dry year. The bunch pieces also affected the potato yield. For all the years, the yield was higher for the 2 pieces than the 1 piece. On average, the increasing rate could be 12.9%. The influence of bunch piece was greater in the dry year, humid year and normal year. In 2016 when the whole piece was added, the potato yield was the highest in the whole piece. The potato yield was increased when the rowing space was decreased or the planting density was increased. On average, the potato yield was decreased by 12.76% and 22.95% when the rowing space of 25 cm increased to 35 and 45 cm, respectively. The influence of rowing space was the highest in the normal year, followed by humid and dry year. Among all the treatments, the highest potato yield was 48170.3 kg/hm2 for the treatment of black film with 2 pieces and rowing space of 25 cm. The water use efficiency was 17.1% higher by using black film mulching than white film mulching, and 33.2% higher in the 2 pieces than the 1 piece. Among all the treatments of planting density, the water use efficiency of 25 cm rowing space was the highest (101.9 kg/(hm2?mm)). The water use efficiency was greatly affected by rowing space, film and bunch piece and the influence was highest in the dry year, the normal year and humid year. The influence on the water use efficiency was the highest by the bunch piece, rowing space and film in the humid year, but the highest in the rowing space, film and bunch piece in the normal year. Thus, the suitable cultivation method for potato in dryland was the row spacing of 25 cm, the black film and the whole piece or 2 pieces.