Effects Of Mulching Patterns On Soil Hydrothermal Regimes And Yield Formation Of Potato In Semiarid Rain-fed Ecosystem

Potato?Solanum tuberosum L.?is the main crop in rain-fed cold and dry agricultural area of northwest China.Plastic film mulching is a widely used cultivation technique for drought-resistance and soil moisture conservation in this area.However,plastic film mulching has the problems of soil cumulative pollution and increasing cost,so it is urgently need to develop the technology of replacing or reducing the use of plastic film.Straw mulching is a kind of sustainable green production practice which is ecological and environmental protection,combining planting crop and breeding soil,and can realize straw resource recycling.The northwest cold and dry region is rich in maize straw resources.If the traditional whole-ground straw mulching method is adapted,there are many problems,such as crushing maize straw energy consumption and effort,difficult to remove residual film of maize harvested by machine,and influence potato sowing and harvesting by machine.A field experiment was performed in rain-fed cold and dry agricultural area of northwest China in 2016?dry year?and 2017?normal?year to evaluate the effects of whole maize straw partial coverage and plastic film mulching on growth and development of potato,soil hydrothermal conditions,potato plant water content,photosynthetic characteristic,tuber yield and water use efficiency?WUE?,and this results will provide theoretical basis and technical support for high yield and high-efficiency-green cultivation for potato mulching with whole maize straw.Six treatments were established:RT,alternating large ridges and small furrows with whole maize straw mulched only on furrows.Two rows of potato were planted in the ridges with 0.4 m spacing between rows;RS,alternating large ridges and small furrows with whole maize straw mulched only on furrows.One row of potato was planted in the middle of ridges;PT,alternating the strips mulched with whole maize straw and bare plots with no ridges.Two rows of potato were planted in the non-mulched strips;PS,alternating the strips mulched with whole maize straw and bare plots with no ridges.One row of potato was planted in the middle of non-mulched strips;FM,alternating small and wide ridges both mulched by black polyethylene;CK,traditional-flat planting without mulching.The row distances were all 0.6 m.The main results of this research are as follows:1.Compaed with CK,both plastic film mulching and whole maize straw mulching treatments could significantly improve tuber yield and water use efficiency in dryland potato in both of years.FM and RT produced the highest drying tuber yield,and FM and RT increased drying yield on average by 53.8%and 52.0%,respectively,compared with CK in two years.The drying tuber yield of RT and FM had no significant difference in both two years,indicating that the suitable whole maize straw mulching practice could reach the tuber yield level of PM.According to the analysis of whole maize straw partial mulching patterns,the yield of RT and PT treatments was larger than that of RS and PS treatments,respectively,and the furrow mulching with whole maize straw?RT and RS?treatments was larger than that of flat mulching with whole maize straw treatments?PT and PS?.Analysis mulching practices production mechanism,regardless of drought or normal year,under the condition of the same density,from the point of view of tuber yield composition components mainly mulching siginificantly improved the potato weight?r=0.883**⁰.980**?.The average weight of single potato in mulching treatments in two years was 42%higher than that of CK,and the increase of RT and FM was the largest?56%⁶2%?,while the tuber number per plant in mulching treatments was slightly lower than that of CK.The weight of single potato formed in the later stage had a strong compensation effect on the insufficient number of tuber in the early stage.From the point of view of vegetative growth and reproductive growth,the main reason for increasing yield by mulching was that it significantly promoted vegetative growth.The average growth per plant of mulching treatment was 38%higher than that of CK in both of years,and the increase of RT and FM was the largest?58%⁵9%?.The yield was highly positively correlated with the growth per plant?r=0.946**⁰.989**?,while the harvest index was relatively stable.At the same time,mulching practices also significantly increased the big tuber rate?BR?and commodity rate?CR?,in which the BR and CR of RT were the highest in mulching treatments,and the BR of RT was15.7 and 7.4 percentage point higher than that of CK and FM,respectively.The CR of RT was21.2 and 5.8 percentage points higher than that of CK and FM,respectively.2.The soil temperature of potato field was significantly affected by mulching practices.Compared with CK,mulching had a general warming effect,while straw mulching had a general cooling effect.Compared with the average temperature of 5²5 cm during the whole growth period,FM was 1.03?dry year?and 1.51??normal year?higher than that of CK,respectively,while the average temperature of four whole straw partial mulching treatments was 1.68??dry year?and 1.46??normal year?.There was no difference in soil temperature among the whole maize straw partial mulching practices.Further analysis showed that both whole maize straw partial mulching and plastic film mulching treatments had the"double effect"of warming and cooling,compared with CK,but the warming effect of mulching was greater than that of cooling effect,and the cooling effect of whole maize straw partial mulching was the opposite.In drought and normal years,the proportion of temperature increasing points?times?of plastic film mulching was 82.9%and 85.7%respectively,while the proportion of temperature decreasing points?times?of four straw mulching practices was 95.0%and 90.0%,respectively.The proportion of temperature increasing points?times?of plastic film mulching was 82.9%and 85.7%respectively.The cooling effect of plastic film mulching was mainly at tuber initiation stage,while the warming effect of whole maize straw partial mulching was mainly at seedling stage.FM also significantly increased the soil accumulated temperature during the whole growth stage.FM increased the effective accumulated temperature of 122.0?in dry years and 179.9?in normal years,respectively,compared with CK,which shortened the whole growth period by about 6 days.Compared with CK,four whole maize straw partial mulching decreased accumulated temperature on average by 208.9?in dry year and 156.1?in normal year,respectively,and the growth period was prolonged by 7¹2 d under straw partial mulching practices.Correlation analysis indicated that reducing soil temperature could significantly improve plant water content.Soil temperature had little effect on tuber number at tuber formation stage,but soil temperature at tuber expansion stage had no significant effect on tuber weight.However,the cooling effect of straw mulching was the main reason for the increase of big tuber rate and single tuber weight.3.Mulching significantly improved soil water supply capacity,and RT had the highest soil water storage in 0² m depth in both of years.Compared with CK,the magnitude of soil water storage in 0² m depth in whole maize straw partial mulching practices increase was larger than plastic film mulching,normal year was larger than drought year,plating two rows was similar to single row under straw partial mulching pratcices,straw mulching only on furrows and flat mulching were not consistent between dry and normal years.The precipitation infiltration rate in maize straw partial mulching practices was significantly higher than that of FM.The precipitation infiltration rate under straw partial mulching practices was 43.3percentage points higher than that of FM on average in four precipitation events.There was no significant difference in straw infiltration rate between RT,PT treatments and CK,and all of them are as high as 90.0%.Whole maize straw strips mulching belongs to partial mulching model,and the effect of soil moisture conservation was certainly not as good as that of PM,but straw mulching had the obvious advantages of improving precipitation infiltration rate and cooling and steam suppression,which was the main reason why the soil moisture status in straw mulching was better than that of FM.At the same time,it was also found that whole maize straw partial mulching and FM had the dual effects of increasing soil moisture and reducing soil moisture,compared with CK.Improving soil moisture status was the main reason for increasing yield by mulching practices.Soil moisture was positively correlated with plant and its organ water status,plant nutritional growth and single potato weight,and soil moisture was most significantly affected by tuber initiation and expansion stage.At the same time,it was found that deep water supply played an important role in potato production in dryland.The dependence of potato growth and yield formation on deep water supply below 40 cm was significantly higher than that the upper?0⁴0 cm?soil layer.Mulching treatments also significantly changed the structure of water consumption.Compared with CK,mulching significantly decreased the water consumption ratio in the early stage?emergence to tuber formation?and increased the water consumption ratio in the middle and late stage?tuber formation to maturity?,which was the main reason why mulching practices significantly increased the single tuber weight and then increased the tuber yield.The consumption of soil water storage was mainly concentrated in the range of 0¹.2 m soil depth,but the soil water consumption under 1.2 m could be obviously reduced by mulching and precipitation.4.There was an obvious interaction regulation effect on soil water temperature.0²5 cm layer temperature was negatively correlated with 0⁴0,40¹20,120²00 and 0²00 cm soil water content,but the negative correlation degree increases gradually with the increase of soil depth,which indicated that on the one hand,it showed that the surface temperature could obviously affect the migration and transfer of deep water,and on the other hand,the upper soil was greatly affected by precipitation and air temperature.5.Mulching could significantly improve the photosynthetic rate?Pn?.During tuber initiation stage,the instantaneous water use efficiency of leaves?WUE_L?,photosynthetic electron transfer efficiency?ETR?and photochemical quenching coefficient?qP?were significantly higher than those of CK.However,during tuber bulking stage,the Pn,WUE_L,?PS?,ETR and qP in straw partial mulching treatments were significantly higher than those with FM and CK.The intracellular CO₂ concentration?Ci?and transpiration rate?Tr?,N content of leaves?L_N?,leaves SPAD value were different with different growth stages at tuber bulking stage.In the key stage of tuber expansion and weight gain,higher?PS?,ETR,qP,SPAD value,Ci,L_N,WUE_L,Tr and Gs,were maintained,especially the chlorophyll fluorescence reaction parameters??PS,ETR,qP?were increased.It was the direct physiological reason for leaves to maintain high Pn,and the delayed senescence of leaves caused by straw mulching and cooling was the indirect external cause of straw mulching to maintain high Pn at tuber bulking stage.