| Sugar beet is an important sugar crop in China.It has the characteristics of drought,cold and saline resistance.In recent years,the planting area of sugar beet in Inner Mongolia has increased greatly,and the arid area is the main area for expanding planting of sugar beet.Water supply in the dry farming area is based on natural precipitation,and there is no irrigation condition in the whole growth period.So wateris the main factor restricting the growth of sugar beet in arid areas.Full film mulching is an effective measure for crop cultivation in arid areasdue to its functions of increasing temperature,preserving moisture and pressing grass which can not only improve the microenvironment of crop growth,but also improve soil moisture content,optimize crop growth indicators and promote the formation of crop yield and quality further.In order to explore the film mulching mode,suitable nitrogen application and planting density for high yield and sugar content of rainfed sugar beet the,physiological effects of film mulching modes on dry-farmed sugar beet and nitrogen-density coupling on sugar beet with full-film-mulched treatment were studied,which would provide a new technology and theoretical basis for rainfed sugar beet with high yield and sugar content.The results show that:1.Under dry farming conditions,film mulching treatment showed good water-keeping and heat preservation capacity,there into,the full-film mulching treatment showed better performance.The yield and sugar yield of full film mulching treatment were significantly different from those of semi-film mulching and non-film treatment(P<0.05).The yield of full-film mulching treatment was increased by 14.8-22.7%compared to semi-mulching treatment and 25.4-43.5%compared to non-film mulching treatment in two years.2.Under dry farming conditions,the leaf area index(LAI),dry matter a ccumulation per plant,SPAD value and net photosynthetic rate of full-film tr eatment were significantly increased compared to semi-film mulching and non-film mulching ones.Grey relation analysis showed that there was a high cor relation degree between leaf area index,SPAD value and the yield of sugar beet under full-film mulching condition.,which could be used as a reference index for high yield in Inner Mongolia dryland region.3.Under dry farming conditions,the chlorophyll fluorescence F0 value a nd qN value of different film mulching treatments showed that the full-film mulching<semi-film mulching<no film mulching,and no film mulching c ould cause water stress in sugarbeet and then inhibit the growth of sugarbee t.4.Under dry farming conditions,full-film mulching treatment had higher N physiological efficiency and N agronomic efficiency than those under semi-film mulching and non-film mulching ones.The partial productivity of nitrogen fertilizer under full-film mulching treatment increased in the range from 104 to 113 kg/kg in two years;the partial productivity and agronomic efficiency of nitrogen fertilizer under 120 kg/hm2 N application and 91,000 plant/hm2 N planting density were higher.5.Under dry farming conditions,the leaf area index,SPAD value,net p hotosynthetic rate,transpiration rate and nitrogen and phosphorus uptake of s ugarbeet were significantly affected by nitrogen-dense coupling treatment.The yield of sugar beet could be increased when the leaf area index,SPAD valu e and net photosynthetic rate were higher than 4,43 and 23 micromol/(m2.s)respectively in the period of root candy growth.6.The multivariate regression equation of yield,sugar content,sugar yie Id and nitrogen density of Sugarbeet covered with plastic film under dry far ming was established as follows:YYield=50981+166X1+2.6X2-8.5X12-0.01X22-1.7X1X2;YSugar content=16.5+0.1966X1+0.0025X2-0.010X12-0.0000136X22-0.000084X1 X2;YSugar yield-8406+87.3X1+8.1X2-4.5X12-0.03X22-0.2X1X2;For rainfed sugar beet with full-film mulching,beet yield,sugar conten t and sugar yield could reach up to 65000 kg/hm2,17.4 and 11000 kg/hm2 re spectivelywhen planting density and nitrogen application rate were 98000 plan ts per hm2?130kg/hm2;98300 plants per hm2?91.9kg/hm2;97000 plants per hm2?135kg/hm2. |
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