Effect Of Supplementary Irrigation On Yield And Feeding Qualityof Grain And Forage Maize In Rainfed Area

Facing the pressures of increasing demand for grain and forage and decreasing of water resources, it has become the inevitable choice to pay more attention to the development of maize with grain and forage for the sustainable development in rainfed area of the Loess Plateau. Currently, many researchers mainly focused on the study on technology and theory of maize production. However, little research pays close attention to promoting the yield and feeding quality of maize with grain. In this study, the influence mechanism of supplementary irrigation levels(0mm, 45 mm, 90 mm and 135mm) on grain yield, straw forage quality and water use efficiency(WUE) at the key stage of maize growth and development was conducted under the treatments of the integrated application of limited irrigation and different maize varieties in rainfed area of the Loess Plateau, with the aim of providing a theoretical basis for the promoting the yield and feeding quality of maize with grain, WUE under supplementary irrigation in the semi-arid region of Loess Plateau. And the results are as follows:1. There was a significant difference in the effect of supplementary irrigation level, genotype and their interaction on maize yield. In the normal rainfall years, the maize grain yield and biomass increased by 20.1%, 16.0% and 16.8%,13.7%(P<0.05) at the supplementary irrigation levels of 135mm/hm2 and 45mm/hm2 compared to the without supplementary irrigation, respectively. In the deficit rainfall years, the maize grain yield and biomass increased by 29.4%, 23.3%, 16.4% and 49.8%, 39.3%, 22.7%(P<0.05) at the supplementary irrigation levels of 135mm/hm2, 90mm/hm2 and 45mm/hm2 compared to the without supplementary irrigation, respectively. Under the supplementary irrigation levels of 135mm/hm2, 90mm/hm2 and 45mm/hm2, the maize grain yield of Gannong926 and Gannong565 were higher 33.3%, 19.6% and 37.7%, 23.6%(P<0.05) than that of Gannong256 and Gannong340; and that of biomass were higher 36.0%, 32.0% and 39.1%, 35.0%(P<0.05) in both of the normal and deficit rainfall years. Take into the interaction of supplementary irrigation level and genotype consideration, the highest grain yield and biomass of Gannong926 and Gannong565 could be obtained at the supplementary irrigation levels of 45mm/hm2,135mm/hm2 and 90mm/hm2, 135mm/hm2, respectively, in both of the normal and deficit rainfall years.2. Under the different supplemental irrigation levels, leaf area indexes and net assimilation rates showed the trend of increasing at the first growth stage and then decreasing at the last growth stage, the leaf area index reached max value at the tassel stage, meanwhile the leaf area indexes of Gannong926 and Gannong565 not only be enhanced at the first growth stage, but also be maintained a high level at the last growth stage. With the increasing of supplemental irrigation levels, the photosynthesis reduced and the net assimilation rate increased, and the relative growth rate could be regulated from grain filling stage to maturity stage. Both of the SPAD value and chlorophyll content could be promoted with suitable supplemental irrigation levels. There were significant effects on the photosynthetic characteristics in the difference genotype maize, the photosynthetic rate of Gannong926 and Gannong565 increased by 30.3%, 39.7% and 13.4%, 5.8%(P<0.05) compared to Gannong256 and Gannong340; the transpiration rate of Gannong926 and Gannong565 increased by 41.5%, 46.5% and 27.5%, 32%(P<0.05) compared to Gannong256 and Gannong340; the intercellular CO2 concentration of Gannong926 and Gannong565 increased by 25.9%, 16.3% and 15.5%, 6.6%(P<0.05) compared to Gannong256 and Gannong340. The transpiration rates were significantly affected at the tassel stage under the different supplemental irrigation levels, and the 90mm/hm2 irrigation level significantly reduced the transpiration rate.3. There were a significant regulatory effect of supplementary irrigation on total relative accumulation and quality of maize. The content of acid and neutral detergent fiber in both of leaves and stems showed the increasing trend at the growth stages, the content of acid detergent fiber in ears increased, while the content of neutral detergent fiber decreased. At the maturity stages, both of the content of crude protein and acid and neutral detergent fiber were accumulated with the increasing supplemental irrigation levels. In the normal rainfall years, the content of crude protein could be improved, while the content of acid and neutral detergent fiber in stems and grain could be inhibited with supplementary irrigation. In the deficit rainfall years, the content of crude protein in leaves and grain could be improved, while the content of acid and neutral detergent fiber in leaves and eras could be inhibited with supplementary irrigation, which was conducive to improve the forage quality. There was a significant positive relationship between dry biomass of different organs and the content of crude protein, acid and neutral detergent fiber, except for the relationship of dry biomass with the content of crude protein, acid and neutral detergent fiber in the sheath in the deficit rainfall years. Above of which indicated that there was a complicated relationship among of the dry biomass, crude protein, acid and neutral detergent fiber in different organs.4. The maize WUE characteristics were also significantly affected by the supplemental irrigation levels, genotype and their interactions. In both normal and deficit rainfall years, the water consumption of maize increased with the amount of supplemental irrigation, the water consumption amount under the supplementary irrigation levels of 45mm/hm2, 90mm/hm2 and 135mm/hm2 increased by 3.1%-29.4% and 2.0%-28.7%, respectively. The effect of supplemental irrigation on the WUE of grain yield and biomass mainly depended on the growth stages; there was no significant difference in the WUE of grain yield under different supplemental irrigation levels in normal rainfall years, while the WUE of biomass was reduced under the supplemental irrigation levels of 90mm/hm2 and 135mm/hm2. In deficit rainfall years, the WUE of grain yield and biomass under the supplemental irrigation levels of 45mm/hm2 increased by 7.1% and 12.6%(P<0.05) compared to the without supplementary irrigation, respectively; There was no significant difference under the supplemental irrigation levels of 90mm/hm2 and 135mm/hm2, while the WUE of biomass increased by 16.0% and 19.3%(P<0.05) compared to the without supplementary irrigation, respectively. Rainfall use efficiency of Gannong926 could be markedly improved under the supplemental irrigation levels of 45mm/hm2 in the normal rainfall years; and the Rainfall use efficiency of Gannong926 under all of the three irrigation levels could be increased by 17.1%-36.4%(P<0.05) compared to the without supplementary irrigation in deficit rainfall years.