| Object:The management of water and N is vital to increase yield and sugar content of sugar-beet.The effect of different irrigation amounts and N fertilizer application rates on soil nutrients,sugar-beet yield and sugar content were investigated under double film mulching with drip irrigation conditions.The objective of this study is（1）to clarify the coupling effect of water and N on sugar-beet yield and sugar content;（2）to put forward the optimized management of water and N in sugar-beet under double film mulching with drip irrigation.These results could provide the scientific basis for water and N management of sugar-beet in the 9th division of Xinjiang production and construction corps.Methods:The field experiment was conducted at an agricultural experimental station at the agricultural science research institute of the 9th division,EMin,Xinjiang province,during the2013 and 2014 growing seasons.The completed random of single factor of water irrigation was introduced to the experiment No.1.Four irrigation amount treatments were set as 3000,3750,4500,and 5250 m3/hm2（noted as W1,W2,W3,and W4,respectively）.The completed random of two factors with water and N was introduced to the experiment No.2.The irrigation amounts were3000,4500,and 6000 m3/hm2（noted as W1,W2,and W3,respectively）.The N application rates were 0,150,and 300 kg/hm2（noted as N0,N1,and N2,respectively）.Results:（1）The water content,leaf area index,and SPAD of sugar-beet reduced significantly under low irrigation treatment（W1,3000 m3/hm2）.Compared with W1 treatment,the water uptake and leaf growth of sugar-beet were promoted under W2,W3,and W4 treatments.The yield of sugar-beet in the W3 and W4 treatments were significantly higher than that in W1,but there was no significant difference between W2 and W1 treatments.Sugar content decreased with irrigation amount increased.Compared with W1 and W2 treatments,sugar content in the W4 treatment（5250 m3/hm2）was decreased by 0.8 and 1.1 percentage points,respectively.The highest of sugar yield was found in W3 treatment（4500 m3/hm2）in this study.（2）The application of N fertilizer increased soil organic matter and available N concentrations,but the concentrations of soil available P and K were not influenced by N application.Soil organic matter and available N concentrations in the 0-40 cm soil layer were significantly higher in the N2 treatment than in the N0 treatment.The concentrations of soil organic matter,and available N,P,and K were reduced when irrigation amount increasing from3000 to 4500,and to 6000 m3/hm2.Soil organic matter and available N,P,and K concentrations in the 0-20 cm soil layer were significantly lower in the W3（6000 m3/hm2）treatment than those in the N0 treatment.（3）Water irrigation and N fertilizer application promoted the growth and nutrient uptake of sugar-beet,and increased the dry matter accumulation.The ratio of root/shoot,however,decreased with irrigation amount and N application rate increased.The root/shoot ratio in the N2W3treatment（300 kg/hm2,6000 m3/hm2）was 66.8%lower than that in the N0W1 treatment（0 kg/hm2,3000 m3/hm2）.The increase of nitrogen application rate and irrigation amount significantly increased N uptake of sugar beet,and showed a positive interaction effect of water and nitrogen.In this study area,the effects of irrigation amount on dry matter accumulation and P,K uptake of sugar beet was greater than that of N fertilizer.（4）The suitable irrigation amount and N application rate had no significant influence on sugar content,but the excessive water irrigation（>4500 m3/hm2）and N application（>150 kg/hm2）significantly reduced sugar content.Compared with N0 and N1 treatments,sugar content in the N2 treatment was decreased by 3.2 and 4.1 percentage points,respectively.（5）The sugar-beet yield and sugar yield were significantly affected by both irrigation amount and N application rate,but not by the interaction of water and N.The order of sugar-beet yield under different irrigation or N application treatments was followed as:W2,W3>W1;N1>N2,N0.Sugar yield was significantly higher by 14.4%in the w2 treatment（4500 m3/hm2）than in the W1treatment（3000 m3/hm2）.There was no significant difference in sugar yield between the W2treatment and the W3 treatment（6000 m3/hm2）.The highest of sugar-beet yield was found in the N1 treatment,which represented 22.6%higher than that in the N0 treatment.The least of sugar yield was found in the N2 treatment,which was 20.1%less than that in the N0 treatment.The treatment of W2N1(water irrigation 4500 m3/hm2 combined with N application 150 kg/hm2)had the highest of sugar-beet yield and sugar yield in this study.Conclusions:Both water irrigation and N fertilization can promote sugar-beet growth and increase the yield of sugar-beet.Excessive irrigation and N application not only do not increase yield of sugar beet,but also reduce the sugar content,and hence decrease sugar yield.In the study area,the optimum management of water and nitrogen for sugar beet is water irrigation 4500 m3/hm2combined with N application 150 kg/hm2 under double film mulching with drip irrigation. |
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