| Foxtail millet (Setaria italica L.) is of high nutritious value, which has been mostly used for foods in Africa and Asia or Central and South America. However, with the reason like low yield and so on, millet is reduced to the insignificant minor grain crops. Especially the planting area is shrinking year by year. Since the1990s, a series of varieties bred hybrid millet significantly increase production levels. To improve the millet’s yield, not only the variety improvement is needed, but also the matching of the fine seed and the fine method, which could fully digs the yield-increasing potential of the fine seed. As a result, the cultivation measures should be adopted if giving full play to the superiority of the high-yield hybrid millet. To investigate the effects of nitrogen level, phosphate level, potassium level, line spacing and plant spacing on growth and development, carbon and nitrogen metabolism enzyme activity, photosynthetic characteristics and yield components of Zhangzagu5, we conducted an experiment based on5-factor quadratic general rotary unitized design with three replications. In this study, the main contents and results are as follows:(1) The correlation between eight main agronomic characters and yield was analyzed by the grey relational grade analysis methods. The results showed that relational order was as follows:leaf area index>ear length>branch number>ear yardage>ear diameter>plant height>stem diameter>node length. The level of nitrogen had significant effects on plant height, branch number, node length, leaf area index, and ear length. And plant height and node length were promoted and branch number, leaf area index and ear length had a trend from rising to declining with nitrogen increasing. With phosphate increasing branch number increased at first and then decreased. The level of potassium had significant effects on plant height, stem diameter and node length. And with potassium increasing, plant height and node length were promoted and stem diameter had a trend from rising to declining. Plant height, branch number, ear diameter, ear length and ear yardage have a trend from rising to declining with row spacing narrowing. With plant spacing narrowing, branch number, stem diameter and ear length were decreased after increasing. With row spacing widening stem diameter and node length were promoted. With plant spacing widening node length also was promoted. The interaction between the nitrogen level and row spacing showed significant effect on ear length, and the combination of high-fertilizer and high-density was benefit from improving ear length. The interaction between the potassium level and row spacing had great effect on ear diameter, while the interaction between phosphate level and plant spacing showed significant effect on plant height. The interaction between the row spacing and plant spacing had significant effect on ear yardage, as well as the configuration of narrow row spacing and wide plant spacing or wide row spacing and narrow plant spacing is conducive to the increase in the number of ear yardage. Rational planting and proper fertilization, could regulate leaf area index in the most appropriate, and promote tillering, and make basal stubby. This study recommended in the mid-fertilizer and mid-dense, that growth and development of the foxtail millet can achieve a better state.(2) The levels of nitrogen, phosphate and row spacing had significant effects on soluble protein, soluble sugar and activity of nitrate reductase, and soluble protein, soluble sugar and activity of nitrate reductase had a trend from rising to declining with nitrogen, phosphate increasing and row spacing narrowing. Variations of these three traits are complementary. Soluble protein increased, which could improve the activity of key photosynthetics and photosynthetic capacity. Further, photosynthesis, the content of soluble sugar and dry matter accumulation were increased. With the content of soluble protein increasing, the response of plants on inorganic fertilizer is more sensitive, and the utilization of nitrogen increases, and the activity of nitrate reductase enhanced. The level of potassium showed a significant effect on soluble sugar, and with potassium increasing, the content of soluble sugar decreased rapidly after rise slowly. The interaction between potassium of level and plant spacing showed great effects on the content of soluble and activity of nitrate reductase. Under low potassium condition, the content of soluble protein and the activity of nitrate reductase were regulated by increasing the planting density. The combination of high-fertilizer and high-density was not benefit from improving the content of soluble protein and the activity of nitrate reductase. On the basis of narrow row spacing and moderate density, by increasing nitrogen and phosphate and selecting the appropriate application periods, the content of soluble protein, the content of soluble sugar and the activity of nitrate reductase could be increased, so as to achieve higher yield and quality improvement.(3) Maximize the utilization of light energy is the main way to increase crop yields. Many factors affect photosynthesis. Nitrogen, phosphorus, potassium, line spacing, and spacing are important factors affecting photosynthesis. The results show that the level of nitrogen had significant effects on chlorophyll content (SPAD)(Ch1), net photosynthetic rate (Pn), intercellular CO2concentration (IntCO2), electron transport rate (ETR), effective photochemical quantum yield (Y(Ⅱ)), coefficient of photochemical fluorescence quenching (qP), coefficient of non-photochemical fluorescence quenching (qN) and maximum photochemical quantum yield (Fv/Fm) of millet. And Ch1, Pn, IntCO2, Y (Ⅱ) and qP had a trend from rising to declining with nitrogen increasing; With nitrogen increasing qN decreased at first and then increased and Fv/Fm was promoted. The effects of phosphate level on Pn, ETR, Y (Ⅱ) and qN are evident, which had a trend from rising to declining with phosphate increasing. The effects of potassium levels on Pn, evapotranspiration (E), stomatal conductance (C), IntCO2, ETR, Y(Ⅱ) and qP are obvious. The row spacing had great effects on Pn, E, C, IntCO2, ETR, Y (Ⅱ), qP and qN. And Pn, E, C, IntCO2, ETR, Y (Ⅱ) and qP had a trend from rising to declining, but qN was increased after decreasing with row spacing narrowing. The effects of plant spacing on all indexes were not significant. The interactions between the nitrogen level and potassium level show significant effects on Pn, IntCO2, ETR,Y(Ⅱ) and qP, and the interactions between the nitrogen level a and plant spacing show great effects on Pn, IntCO2and ETR, while the interaction between potassium level and plant spacing showed great effect on Pn and IntCO2. The interaction effects of other factors on chlorophyll content, photosynthetic characteristics and chlorophyll fluorescence kinteics parameters were not obvious. Multivariate quadratic regression analysis indicates that the regression relationship between the levels of nitrogen, phosphate and potassium, row spacing, plant spacing and all index of Zhangzagu5, can be used for production forecasts.(4) Higher photosynthetic carbon assimilation is the premise of high yield of crops. Foxtail millet hybrid was a breakthrough achievement of the field of foxtail millet study in recent years. Compared with conventional foxtail millet, foxtail millet hybrid increase rate of yield is about39.6%, but research on the millet photosynthetic advantage of foxtail millet hybrid has not been reported. In this study, the photosynthetic characteristics were compared between Zhangzagu5and Jingu21in jointing and filling stages. The results indicated Zhangzagu5had higher net photosynthetic rate(Pn) than Jingu21in jointing and filling stages; The differences of chlorophyll content (SPAD)(Ch1), intercellular CO2concentration (IntCO2), evapotranspiration (E); stomatal conductance (C) and coefficient of photochemical fluorescence quenching (qP) between Zhangzagu5and Jingu21were assessed in filling stages, but not in jointing stages. The difference between Zhangzagu5and Jingu21was marked for effective photochemical quantum yield (Y (II)) in jointing and filling stages, but not for electron transport rate (ETR). In filling stages, Jingu21had higher coefficient of non-photochemical fluorescence quenching (qN) than Zhangzagu5. The difference of maximum photochemical quantum yield (Fv/Fm) between Zhangzagu5and Jingu21was significant in jointing and filling stages. The change of parameter is little, and it is not subject to the variety and growing conditions. In summary, the hybrid heterosis of foxtail millet hybrid in large part was reflected on the photosynthetic characteristics. Growth and development of plant can not be separated from photosynthesis, because photosynthesis is the material basis of the substance metabolism and energy metabolism in biosphere. Zhngzagu not only able to capture more light but also fully use of captured light energy for photosynthesis. The main reason that Zhangzagu5has higher yield than Jingu21, is photosynthetic advantage of Zhangzagu5.(5) The results demonstrated that the yield was significantly positively correlated with ears per ha, grains per ear, ear weight, ear grain weight and grain percentage, but not with1000-grains weight. And the order was:grains per ear>grain percentage>ear grain weight>ear weight>ears per ha>1000-grains weight. The level of phosphate and potassium had significant effects on ear grain weight. The effect of phosphate level on ear grain weight was significant in5%probability level. The levels of nitrogen and phosphate all showed significant effects on grain percentage. The levels of nitrogen, phosphate and potassium and the row spacing all showed significant effects on grains per ear and yield, and the grains per ear and yield were mainly affected by nitrogen level and row spacing, and less affected by phosphate and potassium levels. Row spacing, plant spacing and nitrogen level had great effects on ears per ha, which was promoted with increasing N and decreasing row spacing and plant spacing. The effect of phosphate level on1000-grains weight was evident, which had a trend from rising to declining with phosphate increasing. The interactions between nitrogen and row spacing and plant spacing, between phosphate and potassium and plant spacing, between row spacing and plant spacing had significant effects on ear weight. The interactions between nitrogen and plant spacing and between phosphate and potassium showed significant effects on ear grain weight. The interactions between nitrogen and potassium levels and plant spacing, and between potassium level and plant spacing showed significant effects on grains per ear and yield, while the interaction between nitrogen level and plant spacing showed great effect on1000-grains weight. The interaction effects of other factors on the yield and yield components were not so obvious. Multivariate quadratic regression analysis indicated that the regression relationship between the levels of nitrogen, phosphate and potassium, row spacing, plant spacing and the yield of Zhangzagu5, can be used for production forecasts. The recommended cultivation conditions for Zhangzagu5are178-197kg ha-1for nitrogen level,88～101kg ha-1for P2O5,54～67kg ha-1for K2O,22～24cm for row spacing, and12-13cm for plant spacing. In conclusion, nitrogen, phosphate and potassium, row spacing, plant spacing and their interactions have certain effects on the ears per ha, grains per ear,1000-grain weight and yield of Zhangzagu5. Proper planting density and fertilization can successfully resolve the contradictions of ears per ha with grains per ear and1000-grain weight, and increase yield. The research lays a theoretical foundation for reaching high and stable millet yield and spreading hybrid millet to a large area. |
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