Effects of Mulching Patterns on Soil Hydrothermal Regimes and Yield Formation of Potato in Semiarid Rain-fed Ecosystem
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【Author in Chinese】 陈玉章；
【Author's Information】 甘肃农业大学， 作物栽培学与耕作学， 2019， 博士
【Abstract in Chinese】 马铃薯是我国西北雨养寒旱区的主要作物,地膜覆盖是该区广泛使用的抗旱保墒栽培技术,但地膜覆盖存在土壤累积性污染和增加成本问题,急需研发地膜替代或减量使用技术。秸秆覆盖是一种生态环保、种养结合、可实现秸秆资源化循环利用的可持续绿色生产技术。西北寒旱区玉米秸秆资源丰富,若采取传统全地面秸秆碎段覆盖方式,存在粉碎玉米秸秆耗能费力、机收玉米残膜难以清除、影响马铃薯机播机收等诸多问题。为此,本研究在西北雨养寒旱条件下,于2016（干旱年）和2017（平水年）在甘肃省定西市通渭县旱作马铃薯主产区,以传统裸地平作种植（CK）为主对照、生产上主推的黑色地膜全地面覆盖（简称全膜覆盖:FM）为副对照,设置了4种玉米整秆带状覆盖模式,分别为:沟覆垄播双行（RT）、沟覆垄播单行（RS）、平覆双行（PT）和平覆单行（PS）。研究了不同覆盖模式对马铃薯的生长发育状况、土壤水分、土壤温度、植株水分及叶片光合生理、块茎产量及水分利用效率的影响,以期为秸秆整秆覆盖马铃薯高产高效绿色栽培提供理论依据和技术支撑。主要结果如下:1.覆盖较裸地种植（CK）能显著提高旱地马铃薯产量和水分利用效率,以全膜覆盖（FM）和沟覆垄播双行（RT）增产最显著,FM和RT两年分别平均较CK增产（干薯）53.8%、52.0%,但两年度RT和FM间产量均无显著差异（P<0.05）,表明适宜的秸秆覆盖模式可达到全膜覆盖的产量水平。不同秸秆带状覆盖模式间产量比较,总体来讲,覆秆双行>覆秆单行、秸秆沟覆>秸秆平覆。分析覆盖增产机制原因,无论干旱年还是平水年,在密度相同情况下,从产量结构因素角度主要是显著提高了单薯重（r=0.883**0.980**）,覆盖两年平均较CK单薯重提高42%,以RT和FM提高幅度最大（56%62%）,而单株结薯数覆盖反而较CK略有降低,后期形成的单薯重对前期结薯数不足有较强的补偿效应（r=-0.618**-0.725**）;从营养生长和生殖生长角度分析,覆盖增产原因主要是显著促进了营养生长,覆盖处理的单株生长量较CK两年平均提高38%,仍以RT和FM提高幅度最大（58%59%）,产量与单株生长量高度正相关（r=0.946**0.989**）,而收获指数处理间相对较稳定;同时覆盖也显著提高了大薯率和商品薯率,其中RT大薯率和商品薯率均最高,RT大薯率分别高出CK和FM 15.7和7.4个百分点,商品薯率分别高出CK和FM 21.2和5.8个百分点。2.覆盖显著影响马铃薯田土壤温度。与CK相比,覆膜具有普遍的增温效应,而秸秆覆盖具有普遍的降温效应。比较全生育期525 cm平均温度,FM高出CK 1.03（干旱年）和1.51℃（平水年）,而4个秸秆覆盖处理平均较CK降温1.68℃（干旱年）和1.46℃（平水年）,秸秆覆盖模式间土壤温度差异不大。进一步分析发现,随着生育时期和土层的不同,秸秆覆盖和覆膜均不同程度的较CK出现增温和降温的“双重效应”,但覆膜增温效应大于降温效应,秸秆覆盖则相反,在干旱年和平水年,覆膜增温点（次）比例分别为82.9%、85.7%,而4种秸秆覆盖模式的降温点（次）比例为95.0%、90.0%。覆膜的降温效应主要在块茎形成期,而秸秆覆盖的增温效应主要在出苗期。地膜覆盖也明显增加了生育期土壤积温,在干旱年和平水年,覆膜较CK分别增加全生育期有效积温122.0、179.9℃,致使生育期缩短约6 d,而秸秆覆盖较CK分别降低积温208.9℃和156.1℃,生育期延长712 d。相关分析表明,降低土壤温度可显著改善植株水分状况,块茎形成期土壤温度对结薯数影响不大,但块茎膨大期土壤温度显著影响单薯重,降温效应是秸秆覆盖大薯率和单薯重提高的主要原因。3.覆盖能显著提高土壤供水能力,以秸秆沟覆垄播双行（RT）的02 m土壤水分状况最好。比较覆盖较CK在全生育期2 m土体的增墒效果,总体来讲,秸秆覆盖>全膜覆盖,平水年>干旱年,秸秆带状覆盖双行与单行相近,秸秆沟覆与平覆在年际间差异不尽一致。秸秆局部带状覆盖较全膜覆盖显著提高了降水入渗率,秸秆覆盖的降水入渗率平均高出覆膜43.3个百分点,秸秆无论沟覆还是平覆,其降水入渗率与CK无显著差异,均高达90.0%以上。秸秆带状覆盖属于局部覆盖,保墒效果肯定不如覆膜,但由于秸秆覆盖具有提高降水入渗率和降温抑蒸的明显优势,这是其土壤水分状况好于地膜覆盖的主要原因。但同时也发现,随着生育时期和土层不同,秸秆覆盖和地膜覆盖也都程度不等的出现较CK增墒和降墒的双重效应。改善土壤水分状况是覆盖增产的主要原因。土壤水分与植株及各器官水分状况、植株营养生长量、单薯重一般呈明显正相关,土壤水分以块茎形成膨大期对单薯重和产量影响最显著。同时发现深层供水在旱地马铃薯生产中具有重要作用,马铃薯生长和产量形成对40 cm以下深层供水的依赖度显著大于40 cm以上土层。覆盖也明显改变了耗水结构。与CK相比,覆盖显著降低前期（出苗块茎形成）耗水比例,增加中后期（块茎形成成熟）耗水比例,这是覆盖显著提高单薯重、进而提高产量的主要原因;土壤贮水消耗主要集中在01.2 m范围,但覆盖和降水会明显降低1.2m以下土壤耗水。4.土壤水温存在明显互作调控效应。025 cm耕层温度与040、40120、120200、0200 cm土层含水量呈负相关,但负相关程度随土层深度增加逐渐加强,这一方面表明,耕层温度会明显影响深层水分的迁移和调用,另一方面与上层土壤受降水、气温影响较大有关。5.覆盖可显著提高马铃薯叶片净光合速率（Pn）。在块茎形成期,覆盖处理的叶片净光合速率（Pn）、叶片瞬时水分利用效率（WUEL）、实际光化学效率（ΦPSⅡ）、表观电子传递效率（ETR）和光化学猝灭系数（qP）显著高于CK,而秸秆覆盖和地膜覆盖差异不明显;但进入块茎膨大期,秸秆覆盖的Pn、WUEL、ΦPSⅡ、ETR和qP显著高于地膜覆盖和CK。叶片SPAD值、叶片N含量（LN）、胞间CO2浓度（Ci）和蒸腾速率（Tr）随生育时期不同差异不尽一致。在块茎膨大与增重的产量形成关键阶段,维持较高的ΦPSⅡ、ETR、qP、SPAD、Ci、LN、WUEL、Tr和气孔导度（Gs）、尤其是提高叶绿素荧光反应参数值（ΦPSⅡ、ETR、qP）,是叶片保持较高光合速率（Pn）的直接生理原因,而秸秆覆盖降温引起的叶片延迟衰老,是薯重形成期秸秆覆盖保持较高Pn的间接外因。
【Abstract】 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（WUEL）,photosynthetic electron transfer efficiency（ETR）and photochemical quenching coefficient（qP）were significantly higher than those of CK.However,during tuber bulking stage,the Pn,WUEL,ΦPSⅡ,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（LN）,leaves SPAD value were different with different growth stages at tuber bulking stage.In the key stage of tuber expansion and weight gain,higherΦPSⅡ,ETR,qP,SPAD value,Ci,LN,WUEL,Tr and Gs,were maintained,especially the chlorophyll fluorescence reaction parameters（ΦPS,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.