Study On The Productivity,Water,Fertilizer And Heat Use Efficiency,and Benefits Of Main Forage Systems In The North China Plain

Winter wheat（Triticum aestivum）-summer maize（Zea mays）double cropping system is the traditional agricultural practice in the North China Plain,playing a crucial role in maintaining regional food security.However,the extensive water and fertilizer resource inputs of the system have reduced production efficiency,lowered water,and fertilizer utilization,and increased environmental pollution risk.The North China Plain is also an important area for herbivorous livestock farming in China,however the insufficient supply of high-quality forage production has become a significant bottleneck in the region’s livestock industry development.To address this issue,a field experiment was conducted at the Dry Farming Institute’s experimental station,part of the Hebei Academy of Agricultural and Forestry Sciences,from 2017 to 2022.We established four forage systems:alfalfa（Medicago sativa）system（Alf）,forage triticale（×Triticale Wittmack）-forage corn system（T-FC）,seasonal fallow-forage corn system（F-FC）,and seasonal fallow-Sorghum bicolor×S.sudanense system（F-SS）and used the winter wheat-summer maize system（W-C）as a control.We measured the production performance and resource utilization characteristics of light,heat,water,and fertilizer in the different planting systems.Furthermore,we analyzed the economic benefits,carbon emissions,carbon footprint,and ecological service value of each system.This study aims to provide a theoretical foundation and technical support for optimizing the agricultural system and promoting the adjustment of the grain-economy-feed ternary structure in the North China Plain,which ultimately will help ensure a stable supply of forage and high-quality development of herbivorous livestock farming in the region.The main findings of the study include:1.In terms of dry matter yield,crude protein yield,and food equivalent unit,the five-year average dry matter yields for the Alf,T-FC,F-FC,and F-SS systems were14.4 t ha^-1,29.1 t ha^-1,21.1 t ha^-1,and 19.5 t ha^-1,respectively,with the T-FC system achieving the highest dry matter yield.The fluctuations of annual dry matter yield within the same forage system were impacted by annual precipitation and seasonal distribution.The grain and straw yield for the W-C system reached 16.6 t ha^-1 and16.6 t ha^-1（all straws were crushed and returned to the field）.The 5-year average crude protein yield of Alf,T-FC,F-FC,F-SS and W-C systems was 3.0 t ha^-1,2.3 t ha^-1,1.4 t ha^-1,1.7 t ha^-1 and 1.8 t ha^-1,respectively.The 5-year average food equivalents were 14.4 t ha^-1,20.5 t ha^-1,15.9 t ha^-1,13.2 t ha^-1 and 14.3 t ha^-1,respectively.Compared to the W-C system,the crude protein yield of the Alf system significantly increased by 66.7%,while the economic yield,crude protein yield and food equivalent unit of the T-FC system increased significantly by 75.3%,27.8%and43.4%,respectively.The RFV values for alfalfa,forage triticale,and forage corn were all above 140,indicating excellent forage quality.2.In terms of plant water consumption and the food equivalent unit-based resources utilization of water and heat,compared to the W-C system,the irrigation amounts for the Alf,T-FC,F-FC,and F-SS systems reduced by 275.2 mm,69.4 mm,208.6 mm,and 222.6 mm,respectively,with system water consumption significantly decreasing by 34.0%,9.3%,26.1%,and 27.8%（P<0.05）.The results of the food equivalent unit-based resource use efficiency indicated that,water use efficiency increased by 73.3%,51.7%,59.4%,and 36.7%for the Alf,T-FC,F-FC,and F-SS systems,respectively.Compared to the W-C system,the T-FC system’s light and heat use efficiency increased by 85.2%and 44.6%,while the F-FC system increased by34.7%and 12.1%,respectively.The F-SS system only showed a significant increase in light use efficiency.3.In terms of soil physical and chemical properties and nutrient use efficiency,compared to the W-C system,the Alf,T-FC,F-FC,and F-SS systems reduced nitrogen application by 142.5-447.3 kg ha^-1,phosphorus application by 57.0-135.9kg ha^-1,potassium application by 56.3-135.0 kg ha^-1.After five years of continuous forage crop planting,the soil organic matter,total nitrogen,total phosphorus,total potassium,and available nitrogen contents in the 0-20 cm soil layer were equivalent to those of the W-C system.The apparent surpluses of nitrogen and phosphorus in the T-FC,F-FC,and F-SS systems were 51.0-105.9 and 88.5-91.9 kg ha^-1,respectively,indicating that the nitrogen and phosphorus fertilizer input can be further reduced.Seasonal fallow systems（F-FC and F-SS）had no significant effect on soil bulk density,soil nutrient content,water-stable aggregates,or stability index in the 0-20 cm soil layer,and fallow did not significantly improve soil quality in the short term.The results of the food equivalent units-based fertilizer partial productivity revealed that,the Alf,T-FC,F-FC,and F-SS systems significantly increased the partial productivity of nitrogen,phosphorus,and potassium fertilizers,by 2.0-11.4 times,1.8-4.0 times,and 1.8-4.0 times that of the W-C system,respectively.4.In terms of the economic benefits,carbon emissions,carbon footprint,and ecosystem service value,compared to the W-C system,the economic benefits of the Alf system(31,000 CNY ha^-1),T-FC system(38,000 CNY ha^-1),and F-FC system(29,000 CNY ha^-1)significantly increased by 19.2%,46.2%,and 11.5%,respectively.The carbon emissions of the Alf,T-FC,F-FC,and F-SS systems reduced by 7,126.9kg(CO_2-eq)ha^-1,2,353.8 kg(CO_2-eq)ha^-1,4,899.1 kg(CO_2-eq)ha^-1,and 4,989.7 kg(CO_2-eq)ha^-1,and the carbon footprint per food equivalent unit significantly reduced by 78.7%,48.5%,58.7%,and 51.3%.The Alf system plays the most significant role in reducing carbon emissions.The ecosystem service value of the T-FC system(137,000 CNY ha^-1)was significantly higher than that of the W-C system(110,000CNY ha^-1),while the ecosystem service values of the Alf and F-FC systems were equivalent to that of the W-C system.In conclusion,the forage systems can provide a high-quality forage supply for herbivorous livestock in the North China Plain.By reducing irrigation and fertilizer input,the forage systems improve food equivalent unit output,water and fertilizer use efficiency,and economic benefits of the system,while reducing carbon emissions and delivering good economic and environmental effects.The forage triticale-forage corn system can enhance system productivity,water,fertilizer,and heat use efficiency,economic benefits,and reduce carbon emissions.On the premise of ensuring food security supply,the forage triticale-forage corn system can be recommended for planting in the North China Plain.The results of this study had great significance in optimizing the planting structure of the North China Plain,guaranteeing the safe supply of high-quality forage in the region,and promoting the high-quality development of herbivorous animal husbandry.