| In recent years,water scarcity has become one of the major problems limiting the sustainable development of agriculture in North China Plain(NCP).The conventional winter wheat-summer maize system consumes a large amount of water per year.It is necessary to find new cropping system and explore the resources utilization of different systems,and it is necessary to reduce water consumption while maintaining a high yield level.The maize monocropping system could effectively reduce groundwater consumption,but yield was also greatly reduced.The three crops in two years combines maize monocropping with winter wheat-summer maize system.The total yield was still lower compared with the winter wheat-summer maize system,but the water consumption was also significantly reduced.Whether the yield of the new planting system based on wheat and maize can be further improved is the key to the yield potential of maize.Therefore,this study combines years of experimental data to analyze the optimal sowing date of spring maize and the optimum planting density of spring and summer maize.On this basis,comprehensively evaluate the yield,economic income,groundwater consumption and other indicators of different cropping systems,so as to select water-saving and high-efficiency agricultural system suitable for the water resources situation of this region,aiming at providing theoretical and practical basis for high-yielding and high-efficiency sustainable agricultural production.The main results were as follows:1.The adjustment of sowing date can change the production conditions of light and temperature during the growth period,which has an important impact on the formation of yield.Results of 5 year experiments showed that higher yields were achieved between middle and late sowing compared to the early sowing treatment.Under different sowing dates,a significant negative linear correlation was observed between relative yield and average maximum temperature 5 days pre-silking,and there was a significant quadratic response of relative yield to average maximum temperature 5 days post-silking.An average maximum temperature 5 days post-silking of 31.8? produced the maximum relative yield.Significant quadratic relation was observed between the relative yield and average minimum temperature 5 days,and 10 days before maturity.The maximum relative yield was achieved when the average minimum temperature was 13.0? and 13.6? 5 and 10 days before maturity,respectively.By analyzing the meteorological data for many years,we found that the probability of high temperature occurrence before and after silking in early sowing was higher than that of middle and late sowing,and the probability of low temperature occurrence before maturity in late sowing was significantly higher than that of early and middle sowing.Therefore,the middle sowing treatment was the best choice,and the best sowing date for maize in the North China Plain represented by the Wuqiao area is from mid-May to early June.2.Increasing density is an important cultivation measure to increase maize yield.With the increase of planting density,the yields of ZD958 and HM1 spring and summer maize showed a trend of increasing first and then decreasing,and the leaf area index showed a significant increase trend.However,the net photosynthetic rate and light transmittance of the ear layer showed a significant decrease trend,and the lodging rate showed a significant increase trend.Comprehensive analysis of the relationship between density and relative yield and the relationship between yield,net photosynthetic rate and lodging rate at different densities in the same year can be concluded that when the ZD958 spring maize planting density was 82,500-92,000 plants ha-1 and summer maize planting density was 82,500-86,000 plants ha-1,higher yield could be obtained.The HM1 spring maize planting density was 105,000-106,000 plants ha-1 and summer maize planting density was 97,000-105,000 plants ha-1,which could obtain higher yield.3.In one rotation cycle,the highest yield was achieved under the Con.W/M and Opt.W/M treatment.And it was significantly higher than other treatments.There was no significant difference between the Min.W/M and M-M treatments,but they were significantly higher than the W/M-M and M treatments.Especially in the M treatment,the yield was the lowest.The biomass variation trend of different cropping systems was consistent with the yield,with the highest in Con.W/M and Opt.W/M treatments,and the lowest in the M treatment.The highest utilization rate of solar radiation and temperature resources were the 3 patterns of winter wheat-summer maize cropping systems,followed by M-M,and the lowest was M treatment.4.An increase in the irrigation amount can significantly increase the crop water consumption.The total water consumption of different rotation systems was the highest in Con.W/M,followed by Opt.W/M and Min.W/M.Compared with the 3 patterns of winter wheat-summer maize cropping systems,the water consumption of W/M-M,M-M and M treatments was significantly reduced,and the water use efficiency was significantly improved.According to the principle of maintaining groundwater balance when the groundwater consumption is within 150 mm,the Min.W/M,W/M-M,M-M and M treatments meet the requirements,which can maintain the groundwater balance in the NCP.5.The Con.W/M and Opt.W/M treatments were characterized by high investment,high revenue and high income.The Min.W/M also reduced the annual yield while the irrigation investment was reduced.There was no significant difference in total ecornomic income between Min.W/M and Con.W/M,but it is significantly higher than the W/M-M,M-M and M treatments.Under one rotation cycle,the overall environmental effect was that the M-M treatment has the most serious environmental impact,followed by the Con.WIM,and other treatments have relatively little impact on the environment.Comprehensive consideration of food security,groundwater balance and environmental impact,the Con.W/M and Opt.W/M had higher groundwater consumption and were not sustainable in the future.The M treatment has a significant reduction in groundwater consumption while the yield was also significantly reduced.The M-M treatment has a serious impact on the environment,and early-season maize was susceptible to cold damage.In summary,the W/M-M and Min.W/M treatments were most suitable for the current resources situation,which were the best cropping system for the NCP. |
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