| Aiming at the problems of spring drought,strong evaporation and low water use efficiency in the dry farming areas of southern ningxia,the effects of tillage depth,mulching materials and their interaction on soil physical and chemical properties,potato physiological ecology,yield and water use efficiency in dryland were investigated.A field experiment of different tillage depth[ploughing 15 cm(T1),subsoiling 30 cm(T2),subsoiling 40 cm(T3)and subsoiling 50 cm(T4)]with mulching measures[plastic film mulching(Ml)and straw mulching(M2)]was set in two-factor split plot between October 201 8 and October 2019,and study the effect of tillage with mulching on soil physical and chemical properties,physiological and ecological characteristics of potato,yield and water use efficiency,to explore suitable tillage and mulching measures for potato growth in mountainous area of southern Ningxia,and providing theoretical reference and technical support for building high-yield cultivation for dry potato.The main research results are as follows:(1)Tillage with mulching could increase soil water content at 0-100 cm layer in autumn and winter fallow period,and it had obvious effect on soil water storage.The effect of tillage depth and mulch material on soil water in 0-100 cm layer during potato growth period was significant,while the interaction between tillage depths with mulching material had significant effect on soil water during seedling and tuber growth period.Under the same mulch material,the treatment with 30 cm of subsoiling in potato growth period had the best effect on improving the soil water at 0-100 cm layer,followed by subsoiling 40 cm treatment,and the average soil water storage during the growth period was significantly increased by 5.63%and 3.87%compared with the ploughing 15 cm treatment,respectively.Under the same tillage depth,the soil water storage capacity of plastic film mulch was significantly higher than that of the straw mulch at the early stage of growth(sowing stage to budding stage),and the soil water storage capacity of the straw mulch was significantly higher than that of the plastic film mulch at the middle and late stage of growth(tuber formation stage to harvest stage),which was 6.90%significantly higher than that of the plastic film mulch.Among all treatment combinations,T2M1 treatment got the highest water storage capacity in the early period of growth.However,in the middle and late growth period,T2M2 treatment had the best effect on increasing soil water storage,which was 13.21%higher than T1M1 treatment.(2)Tillage combined with mulching could regulate soil temperature at 0-25 cm layer during potato growth period.The soil temperature with different treatments during potato growth period gradually increased firstly and then decreased,and reached the highest in tuber forming stage.The interaction of tillage depth,mulching material,tillage depth and mulching material had significant effects on soil temperature during period growth.The soil temperature regulation effect with the subsoiling 30 cm and 40 cm treatments under the same mulching material was best.During seedling stage-bud stage and tuber growth stage-harvest stage,plastic film mulching was better than straw mulching under the same tillage depth.Compared with T1M2 treatment,T2M1 and T3M1 treatments significantly increased the temperature by 2.6℃ and 2.1℃ respectively,while T1M1 and T2M2 treatments significantly decreased the temperature by 1.6℃ and 1.1℃,respectively.(3)Tillage combined with mulching could improve the soil physical and chemical properties during the potato harvest stage,and the interaction between tillage depth,mulching material,tillage depth with mulching material had significant effects on the soil physical and chemical properties.Under the same mulching material,the content of>2 mm、0.25～2 mm and>0.25mm mechanical and water-stable aggregates in each layer of 0-40 cm could be increased by the subsoiling 40 cm treatment,followed by the subsoiling 30 cm treatment.The improvement effect with T3M2 treatment was the best.For the improvement of soil bulk density,total porosity and nutrients at 0-60 cm layer,the subsoiling 30 cm treatment has the best effect on reducing soil bulk density,improving soil porosity,soil organic matter,total nitrogen and alkaline hydrolysis nitrogen content,and regulating soil C/N.The straw mulching under the same tillage depth improved the soil physical and chemical properties better than plastic film mulching.Among all the combinations of treatments,T2M2 treatment was the better improvement to improve the soil physical and chemical properties.Compared with T1M1 treatment,T2M2 treatment significantly reduced soil bulk density by 10.98%,and signi ficantly increased soil total porosity and soil organic matter,total nitrogen and alkaline hydrolysis nitrogen content by 8.77%,15.49%,17.91%and 24.26%,respectively.Under the same mulching material,the subsoiling 40 cm treatment had better effect on improving the content of soil available phosphorus,while subsoiling 50 cm treatment had the best effect on improving the soil available potassium content.In all treatment combinations,the content of soil available phosphorus with T3M2 was significantly increased by 54.45%compared with T1M1 treatment,and the soil available potassium content with T4M1 was significantly increased by 38.95%compared with T1M1 treatment.(4)Tillage combined with mulching could effectively improve the physiological activity of roots and chlorophyll photosynthetic performance of leaves during potato critical growth period.The changes of root activity and photosynthetic index of potato leaves during potato critical growth period under different treatments were gradually decreased with the development of potato growth period,while the inter-cellular carbon dioxide concentration in potato leaves was gradually increased.Tillage depth and mulching material had significant effects in root physiological activity of root during key growth period,while the leaf SPAD values in critical growth period was significantly affected by tillage depth.Tillage depth had significant effects on the transpiration rate in tuber bulking stage,mulching material had significant effects on the net photosynthetic rate and transpiration rate in tuber formation stage and transpiration rate in tuber expansion period,the leaf transpiration rate and stomatal conductance in tuber bulking stage with the interactions between tillage depth and mulching material were significantly.Under the same mulching material,subsoiling 30 cm treatment had the best effect on improving physiological activity of roots,SPAD value,net photosynthetic rate of leaves,transpiration rate,and stomatal conductance and reducing inter-cellular carbon dioxide concentration of leaves.Straw mulching under the same tillage depth had better effect on physiological and photosynthetic indexes of potato roots than plastic film mulching.In all tillage with mulching treatments,the inter-cellular carbon dioxide concentration in leaves with T4M2 decreased the most,which was 5.3%lower than that with T1M1 treatment.Among all treatment combinations,T2M2 treatment was the best,and the root active absorption area,leaf SPAD value,net photosynthetic rate,transpiration rate and stomatal conductance in the critical growth period with T2M2 treatment was significantly increased by 30.68%,11.07%,47.57%,50.69%and 82.11%,respectively,compared with T1M1 treatment.(5)The plant height,stem diameter and above-ground biomass during potato growth period under tillage combined with mulching treatments showed a trend of increasing first and then decreasing.The plant height and stem diameter reached the maximum in the tuber expansion stage,while the above-ground biomass reached the maximum in the tuber formation stage.The effect of tillage depth and mulching material on plant height in the early growth stage of potato was significant,but the interaction of the tillage depth and mulching material had no significant effect,and the interaction of mulching material and mulching material had a very significant effect on stem diameter,while the interaction of tillage depth and mulching material had no significant effect on the above-ground biomass during potato growth period.Under the same mulching material,the subsoiling 30 cm treatment was the best for promoting plant height and stem diameter,followed by the subsoiling 40 cm treatment.However,the above-ground biomass of potato was the highest under the subsoiling 40 cm treatment.Under the same tillage depth,plastic film mulching had the best the effect on the potato growth in the early growth stage,while the straw mulching had the best the effect in the middle and late growth stage.Among all treatment combinations,T2M1 and T2M2 treatments had the best effect on promoting plant height and stem diameter,and plant height in the early and middle stages of growth was significantly increased by 14.91%,12.39%and 8.07%and 11.10%,respectively,compared with T1M1 treatment.The improvement of above-ground biomass with T2M1 and T3M2 treatments was the best in the early and middle growth stage,which was 7.51%and 33.38%significantly higher than that with T1M1 treatment,respectively.(6)Tillage combined with mulching could promote the potato growth,and significantly increase potato yield,water use efficiency and economic benefits.The effects of tillage depth,mulching material and their interaction on potato yield and water use efficiency were significant.Under the same mulching material,the order of potato yield was subsoiling 30 cm>subsoiling 40 cm>subsoiling 50 cm>ploughing 15 cm,and the order of water use efficiency was subsoiling 40 cm>subsoiling 30 cm>subsoiling 50 cm>ploughing 15 cm.However,there was no significant difference in yield and water use efficiency among different tillage depths.Under the same tillage depth,the effect of straw mulching on potato yield and water use efficiency was significantly higher than that of plastic film mulching.Among all treatment combinations,T2M2 treatment had the best effect,followed by T3M2 treatment,and T2M2 and T3M2 treatment significantly increased the yield by 37.45%and 33.03%,water use efficiency by 32.24%and 31.01%,economic benefit by 28.67%and 27.42%,output value by 23.88%and 22.86%,and net profit by 30.15%and 28.80%,respectively,compared with T1M1 treatment.(7)Through on potato yield with the indicator principal component analysis,we found that the most critical factor that influenced the potato yield was the above-ground biomass and soil alkaline hydrolysis nitrogen,total nitrogen,available phosphorus and chlorophyll content,root activity and soil total porosity.Among all the treatment combinations,the subsoiling 30 cm with straw mulching had the best effect on increasing potato yield.In conclusion,the subsoiling depth combined with mulching could effectively improve soil physical and chemical properties,enhance the adjustment ability of soil water and temperature,increase crop root physiological activity and photosynthetic performance,significantly promote the growth of above-ground plant,and improve the potato yield,water use efficiency and economic benefit and the subsoiling 30 cm with straw mulching treatment had the best effect. |
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