| Northeast China is one of the four black soil regions in the world.It is endowed with unique natural resources advantages for agricultural development and is also the largest commodity grain base in China.As an important farmland resource,sloping farmland is more than 50% of the black soil area in Northeast China,which is widely distributed with long and gentle slopes.Due to different degrees of not scientific and reasonable soil management measures,soil degradation of black sloping farmland is particularly serious.Over-cultivation of modern agricultural production on sloping farmland has escalated the risk of increasing the soil degradation,thinning of the black soil layer,thickening and hardening of the plough pan,and weakening of the structural stability.In recent years,the area and yield of corn cultivation on black sloping farmland in Northeast China have been continuously increasing.After harvest,the large amount of corn stover retained in the field is difficult to effectively handle has become one of the main problems restricting agricult ural production in this region.As China’s agricultural production has entered the stage of rapid development,how to scientifically select diversified tillage practices,planting systems and crop residue managements to achieve efficient and sustainable development of agriculture has become a hot issue in today’s society.Field experiments were conducted on the typical black sloping farmland under the condition of all corn stover retained in Heilongjiang Province from 2018 to 2019.The split-plot experiment was arranged with three tillage practices(no tillage with corn stover cover,NT;rotary tillage with shallow mixed corn stover,RT;plow tillage with deeply buried corn stover,PT)and two planting systems(corn-soybean rotation,SR and continuous corn,CS).The data of soil penetration resistance,soil bulk density,soil moisture content and soil temperature were measured at four sampling periods(0 d,50 d,100 d and 150 d)of each treatment.The study aims to systematically explore the response law of soil physical property indicators with mechanized tillage planting methods on sloping farmland.Furthermore,combining with unit operation test data and experimental area survey data,the GRA-TOPSIS with coordination correction method is used to evaluate the overall effect of mechanized tillage planting methods from the aspects of technical,economic and ecological effects.The results provide a theoretical reference for the selection of high quality and efficient production mode on the black sloping farmland in cold region.The main contents and results are as follows.(1)An evaluation index system for the effect of mechanized tillage planting methods was established.Based on the index selection principle of comprehensive evaluation index system,combined with the characteristics of mechanized tillage planting methods with corn stover retained on black sloping farmland in cold region,an evaluation index system for the effect of mechanized tillage planting methods associated with corn stubble was constructed.The index system included three aspects,as technical,economic and ecological effects.It contained 15 three-level indexes,including soil disturbance quantity,number of farmland operations,soil compaction degree,seedling emergence rate,working area under labor burden,technical productivity,output value,cost input,investment payback period,net present value,internal rate of return,soil penetration resistance,soil bulk density,soil moisture content and soil temperature.The quantitative data of the evaluation index system could be obtained through field experiments and investigations.(2)Response laws of soil physical characteristics with mechanized tillage planting methods were ascertained.The data of soil penetration resistance,soil bulk density,soil moisture content and soil temperature of different mechanized tillage planting methods were measured through split-plot experiment of sloping farmland associated with corn stubble.Response laws of soil physical characteristics with mechanized tillage planting methods in black sloping farmland of cold region was explored.The results showed that 1)In the 150 d,the average values of the soil penetration resistance in the PT-treated soil at depths of 0–15 cm and 15–30 cm soil were 26.7% and 32.3%lower and 28.2% and 32.3% lower than those of the NT-treated and RT-treated soils,respectively.The soil penetration resistance values in the SR-treated soil at depths of 15–30 cm and 30–45 cm soil were 11.5% and 15.4% lower than that of the CS-treated soil,respectively.In most soil depths,a downward trend in the soil penetration resistance was observed with a change from the upper to the lower slope position.The importance of the influence of various factors on soil penetration resistance is expressed as soil depth> slope position> tillage practice> planting system.2)In the50 d,the average values of soil bulk density in the NT-treated soil at depths of 0–10 cm,10–20 cm and 20–30 cm soil were 15.8%、12.8% and 17.5% significantly higher than those of the PT-treated soil.In the 150 d,the average values of soil bulk density in the NT-treated and RT-treated soils at depth of 0–10 cm soil were 14.7% and 19.7%% significantly higher than those of the PT-treated soil,respectively.There was no significant difference in soil bulk density among NT-treated,RT-treated and PT-treated soils at depths of 10–20 cm,20–30 cm and 30–40 cm soil.There was no significant difference in soil bulk density between CS-treated and SR-treated soils at each depth of0–40 cm soil.In most soil depths,a downward trend in the soil bulk density was observed with a change from the upper to the lower slope position exception of PT-treated soil in 50 d.3)In the 50 d,the average value of soil moisture content in the NT-treated soil at depth of 0–10 cm soil was8.7% significantly higher than that of the PT-treated soil.In the 100 d,the average values of soil moisture content in the NT-treated soil at each depth of 0–40 cm soil was higher than RT-treated and PT-treated soils,although there was no significant difference among three tillage practices.In the 150 d,the average values of soil moisture content in the NT-treated and PT-treated soils at depth of 10–20 cm soil were 10.6% and 10.2% significantly higher than those of the RT-treated soil,respectively.The soil moisture content values in the SR-treated soil at each depth of 0–40 cm soil were 2.3%、0.8%、0.8% and 1.4% higher than that of the CS-treated soil in sampling periods,respectively.In most soil depths,an upward trend in the soil moisture content was observed with a change from the upper to the lower slope position exception of 150 d.The soil moisture content generally showed a significant difference between the upper and lower slope positions.4)In the 0d,the soil temperature value in the PT-treated soil at depth of 0–10 cm soil was 0.54℃significantly higher than that of the NT-treated soil.There was no significant difference in soil temperature among three tillage practices at the other soil depths.In the 50 d and 100 d,there was no significant difference in soil temperature among three tillage practices at each depth of 0–40 cm soil.In the 150 d,the soil temperature values in the NT-treated and RT-treated soils at depth of20–30 cm soil were 0.47℃ and 0.55℃ significantly higher than that of the PT-treated soil.There was no significant difference in soil temperature among three tillage practices at the other soil depths.The soil temperature values in the CS-treated soil at each depth of 0–40 cm soil was 4.8%,3.5%,1.0% and 0.2% higher than those of the SR-treated soil in sampling periods,respectively.In the 0 d,the soil temperature values in the upper and middle slope position soils at depths of 0–10cm and 10–20 cm soil was 0.40℃,0.73℃ and 1.27℃,0.93℃ significantly higher than those in the lower slope position,respectively.In the 150 d,the soil temperature values in the middle and lower slope position soils at depth of 0–10 cm soil was 0.70℃ and 0.58℃ significantly higher than that in the upper slope position,respectively.(3)The effects of different mechanized tillage planting methods on technical effect indexes were compared and analyzed.The data of technical effect indexes of different mechanized tillage planting methods,such as soil disturbance quantity,soil compaction degree,seedling emergence rate and number of farmland operations,were obtained through split plot experiments of sloping farmland associated with corn stubble,and the data rules of technical effect indexes of different mechanized tillage planting methods were compared and analyzed.The results showed that the soil disturbance quantity was the minimum under the NT treatment(33330 mm~2),the next time under the RT treatment(169000mm~2),and the maximum under the PT treatment(338000 mm~2).The number of farmland operations was less under the NT treatment(1 time),but more under the RT and PT treatments(3times).The soil compaction degree was the lowest under the NT treatment(1057 kg/m~2),the next time under the RT treatment(4435 kg/m~2),and the highest under the PT treatment(5875 kg/m~2).Compared with NT and RT treatments,PT treatment significantly reduced corn emergence rate by14.51% and 14.22%,and compared with NT treatment,RT treatment significantly reduced soybean emergence rate by 10.20%.The working area under labor burden was the highest under the NT treatment(2.92 hm~2/person),the next time under the PT treatment(2.51 hm~2/person),and the lowest under the RT treatment(2.34 hm~2/person).The technical productivity was the highest under the NT treatment(0.58 hm~2/h),the nest time under the PT treatment(0.36 hm~2/h),and the lowest under the RT treatment(0.33 hm~2/h).(4)The effects of different mechanized tillage planting methods on economic effect indexes were compared and analyzed.Based on field investigations and experiments,the data of economic effect indexes of different mechanized tillage planting methods,such as production cost input,output value and investment payback period,were obtained,and the data rules of economic effect indexes of different mechanized tillage planting methods were compared and analyzed.The results showed that the output value of soybean was the highest under the NT treatment(8139.3 yuan/hm~2),the nest time under the PT treatment(7498.7 yuan/hm~2),and the lowest under the RT treatment(6318.9 yuan/hm~2).The output value of corn was the highest under the NT treatment(9114.6yuan/hm~2),the nest time under the PT treatment(8392.5 yuan/hm~2),and the lowest under the RT treatment(7228.7 yuan/hm~2).The total input cost of different tillage planting methods was expressed from high to low as PT(corn)and RT(corn)> NT(corn)> PT(soybean)and RT(soybean)> NT(soybean).The payback period was the shortest under the NT treatment(3.1years),the next time under the RT treatment(8.8 years),and the longest under the PT treatment(28.9 years).The net present value was the highest under the RT treatment(501535 yuan),the next time under the PT treatment(460633 yuan),and the lowest under the NT treatment(188563 yuan).The internal rate of return was 12% under both the NT and RT treatments,and only 6% under the PT treatment.(5)The comprehensive effects of different mechanized tillage planting methods was evaluated.Based on the constructed evaluation index system of the effects of mechanized tillage planting methods,the comprehensive effects of six mechanized tillage planting methods were evaluated using the GRA-TOPSIS method modified by coordination degree.The evaluation results showed that the comprehensive effect of mechanized tillage planting methods was evaluated in the order of CS+NT(0.651)>SR+NT(0.642)>SR+RT(0.415)>SR+PT(0.395)>CS+RT(0.381)>CS+PT(0.256).For both corn-soybean rotation and continuous corn,the highest score of comprehensive evaluation was under the NT treatment.The mean score of comprehensive evaluation under the SR treatment was higher than that of CS treatment with three tillage practices.According to the evaluation results,no tillage with stubble mulching should be preferred as tillage practice,and corn-soybean rotation should be preferred as planting system when optimizing mechanized tillage planting method. |
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