In order to investigate the effects of different maize planting densities and plastic film mulching on maize yield

soil water content and root growth in the rain-fed agriculture region of north-eastern China

the field experiment with different planting densities (67 500 plants/hm2

82 500 plants/hm2，97 500 plants/hm2) and film mulching was conducted in the experimental field of Shenyang in 2014—2015. The results showed as follows：（1）In different growth stages of maize

mulching and planting densities had different effects on soil water content in different soil layers. In the upper soil layer of 0—20 cm

soil water content increased by 9.80%

15.93% and 12.77% respectively for three stages (earlier stage

middle stage and later stage) with planning density of 6 7500 plants/hm2. In the soil layer of 20—40 cm

soil water content increased by 13.83% in the early growth stage of maize with planning density of 82 500 plants/hm2

and in the soil layer of 40-60 cm

soil water content (82 500 plants/hm2) increased by 15.47%

4.11% and 8.96% respectively for three stages. (2)The effects of planning density on root length

root project area

root volume and root surface area were significant. This characteristic parameter showed a decreasing trend as the planting density increased. Root length

root project area

root volume and root surface area with the film mulching planting and planning density of 82 500 plants/hm2 increased by 44%，38%，38% and 33% respectively. (3)The grain yield decreased with the increase of planting density. When planting density was 67 500 plants/hm2

the 100-seed weight and grain yield were the highest. The highest 100-seed weight was 36.83 g

and the highest yield was 12 573.69 kg/hm2. These results showed that there was an optimal planning density of maize. Out of this density

the yield of maize decreased with the increase of the planning density. The research provided a theoretical basis for rational selection of optimal planting density and plastic film-mulching

which was also significant to improve rainwater use efficiency and maize yield in rainfed areas in Northeast China.