Effects Of Planting Density On Grain Yield And Water Use Efficiency Of Millet Under Ridge-furrow Rainharvesting Planting Model

In order to explore the effects of planting density on soil temperature, growth process, water consuming characteristics, photosynthetic traits as well as yield performance of foxtail millet under ridge-furrow rainfall harvesting planting model, cv.Datong 29 was field tested in semi-arid Southern Ningxia Province in 2013 and 2014, and 3 planting densities plus a control under flat planting were set. The results of this study can be concluded as following:(1)The increment of average soil temperature of rainfall harvesting treatments was mainly reflected in the ridge side, while increment in the center of furrow was not significant. During grain-filling stage, the average 5~25cm soil temperature of all treatments had no significant difference in both years except for the low density treatment whose soil temperature was 0.87~1.17℃ higher than those of other treatments in 2013.(2)From jointing stage to maturing stage, the biomass of millet individuals all increased with the increase of planting density, while the biomass of millet populations showed an opposite trend. The center of dry matter distribution changed with the alteration of growing center, which began with the leaf, then it turned to the stem and finally it altered to the spike; The ratio of stem and sheath both increased with the increasing of planting density, while the ratio of spike showed an opposite trend at maturing stage, stem and sheath ratios of low density treatment were respectively 26.9% and 18.7% lower than those of high density treatment, and spike ratio was 13.7% higher, thus more dry matter of sheath and stem under low density treatment were transferred into the spike.(3)Compared to sheath, leaf played a more important role in the process of grain forming. Under ridge-furrow rainfall harvesting planting model, dry matter moving rate(MR) and transferring rate(TR) of leaf were both not sensitive to planting density, and their average values were respectively 49.26% and 36.31% higher than those of the CK. MR and TR of the sheath were both negatively related to planting density, MR and TR of the CK lied in between those of middle and high planting density.(4)During grain-filling stage, individual leaf area, Pn and Gs of flag leaf all decreased with the increase of planting density, while leaf area index showed an opposite trend, the largest values of LAI of middle and high density treatment was observed at early grain-filling stage, which reached 3.66 and 4.46 respectively, they were 18.9% and 44.9% larger than that of low density treatment. From the early term to the middle term of grain-filling stage, LAI of all the 3 densities decreased 14.1%~15.7% while LAI of CK diminished only 3.8%.(5) In both years, soil water storage of 0-200 cm underground and soil moisture during jointing stage all decreased with the increase of density, while water consumption during the whole growth period showed an opposite trend, and the middle and high density treatment respectively consumed 5.57% and 10.40% more water than the low density treatment.(6) In both years, grain weight per spike decreased with the rising of planting density, average grain weight per spike of low density treatment reached 23.09 g, which was 13.1% higher than that of middle density treatment, while for middle density treatment, it was 29.9% higher than that of high density treatment; Grain yield increased with the increase of density, the average grain yield of middle and high density treatment was respectively 17.89% and 26.41% higher than that of low density treatment, but the difference between middle and high density was not significant in 2014. Besides, grain yield of CK was respectively 15.97% and 16.85% higher than that of low density treatment in 2013 and 2014, which proved that the increased individual yield couldn’t completely compensate the yield loss induced by the loss of planting area under ridge-furrow rainfall harvesting planting model.(7) With the increase of planting density, WUE in wetter 2013 gradually increased, WUE of high density treatment reached 14.05 kg·mm-1·hm-2, and it was significant higher than those of other treatments which lied in between 11.86~12.69 kg·mm-1·hm-2; while in drier 2014 WUE of middle density was highest, which reached 24.35 kg·mm-1·hm-2, average WUE in 2014 had a gain of 10.37 kg·mm-1·hm-2 compared to that of 2014. WUEs of low density treatment was the lowest in both years, which could be inferred that it was not suitable to adopt low density under ridge-furrow rainfall harvesting planting model in that specific area, because it was not conducive to the enhancing of rainfall utilization rate.