Spatial And Temporal Variation Of Water Footprint And Influencing Factors Under Conservation Tillage Practices Of Maize In Jilin Province,China

Water is a key factor restricting crop growth,and ensuring crop water demand is of great practical significance for ensuring food security in China.Accurately evaluating crop water demand has become one of the research hotspots in crop production in recent years.Water footprint（WF）,as an evaluation method for measuring water use in crop production,has been widely used.However,in most of the studies,the WF accounting method tends to focus only on traditional tillage practices.At present,the impact of conservation tillage on the total and structural water use in crop production is unclear in the context of the widespread implementation and promotion of conservation tillage in China.Therefore,quantifying and evaluating the impact of conservation tillage on water use in crop production is a problem that needs to be solved at present.Jilin Province,as an important maize growing base in China,is both a typical rain-fed agricultural area and the province with the largest area under conservation tillage.This paper selected Jilin Province as the research area,used remote sensing data,meteorological data,statistical data,and survey data as data sources to establish an accounting system for the WF of maize production under different tillage methods,and revealed the spatial and temporal distribution characteristics of the total and structure of WF of maize production under conservation tillage methods,as well as the influencing factors,and clarified the stability and water savings benefits of conservation tillage as a means of maize production,which is of great research significance for ensuring sustainable agricultural development and efficient use of water resources.Based on the Landsat data and elevation data in the Google Earth Engine cloud computing platform,the identification feature set of maize planting area was constructed,and the extraction of maize planting area was realised by using the random forest method.On this basis,Landsat data and survey data were used to achieve the identification of conservation tillage areas.Using the light use efficiency model,the estimation of maize yield per unit area was realised.According to the"WF theory",the blue water footprint(CWF_blue),green water footprint(CWF_green)and total water footprint(CWF_total)of maize production were calculated.Finally,the relative importance evaluation method was adopted to quantify the changes in the relative importance of the influencing factors on the CWF_total of maize production in Jilin Province under different tillage practices.The main findings of the study are as follows:（1）Based on multi-year remote sensing data and survey data,the identification of maize conservation tillage area in Jilin Province from 2010 to 2020 was achieved.2010-2020 conservation tillage area in Jilin Province had obvious spatial and temporal variability.Temporally,with the continuous improvement of conservation tillage technology,the area under conservation tillage in Jilin Province showed a significant increase from 2010 to 2020,and the area under conservation tillage reached 1.19×10⁶ha in 2020,while spatially,conservation tillage was mainly concentrated in the middle region of Jilin Province,where the hydrothermal conditions were suitable and the terrain was flat.（2）Based on remote sensing data and meteorological data,a light use efficiency model was used to achieve the estimation of maize yield in Jilin Province from2010-2020.Temporally,the maize yield in Jilin Province from 2010 to 2020 showed significant fluctuation changed due to unfavorable meteorological factors such as multi-year typhoons and droughts.And the average value of maize unit area yield for many years was 8.13 ton/ha.Spatially,the yield per unit area of maize was significantly higher in the middle region than in other regions.Due to the impact of multi-year typhoons,7.68%of the regions showed a significant decreasing trend in maize unit area yield,mainly concentrated in Gongzhuling City in the middle region of Jilin Province.（3）Based on remote sensing technology,the WF of maize production was accounted for at a spatial resolution of 500 m pixel scale,and it was found that conservation tillage changed the total and structure of the WF of maize production.The CWF_total of maize production was reduced by 10.19%under conservation tillage compared to traditional tillage.Spatially,the CWF_total of maize production was lower in the middle region where conservation tillage was the dominant practice.Moreover,the CWF_total of maize production decreased with the longer years of conservation tillage implementation.The order of the size of the CWF_total of maize production under the three categories of years was:1-3 years（409.12 m³/ton）>4-6 years（396.98m³/ton）>more than 6 years（394.49 m³/ton）.（4）Conservation tillage has changed the relative importance of various factors on the CWF_total of maize production.Compared to traditional tillage methods,the relative importance of total precipitation under conservation tillage has decreased by 1.13%,with a decrease of 1.04%in the relative importance of total precipitation during the milk-ripening stage.At the same time,conservation tillage has also changed the order of relative importance of various factors.Compared to traditional tillage methods,the relative importance order of average temperature under conservation tillage has decreased by four places.In terms of spatial distribution,the percentage of areas where agricultural management factors were the dominant factors affecting the CWF_total of maize production was 11.19%,mainly in the southern part of the middle region of Jilin Province.And the relative importance of total precipitation and average temperature decreased as the number of years of conservation tillage implementation increased.In summary,the area under conservation tillage in Jilin Province was rapidly increasing year by year.Compared with traditional tillage,the WF of maize production under conservation tillage decreased significantly.At the same time,the implementation of conservation tillage reduced the relative importance of precipitation and temperature on the CWF_total of maize production.This indicated that conservation tillage for maize production both saved a certain amount of water for agricultural production and reduced the dependence on total precipitation and average temperature factors.Moreover,as the number of years of conservation tillage implementation increased,the more obvious the water saving and the more obvious the degree of mitigation of total precipitation and average temperature factors’interferenced with the CWF_total of maize production.Therefore,this paper not only enriches and develops the theoretical research on estimating the WF of crop production based on remote sensing technology,but also provides reference for the sustainable production of crops in rainfed areas and the efficient use of agricultural water resources.