Effects Of Deficit Irrigation On Growth,Yield,Tuber Quality And Water Use Of Potato

Gansu Province is an important potato producing area in C hina,with planting area and total output ranking among the top in the country.The main producing area of potato in Gansu Province is Anding District in Dingxi C ity,which is a typical semi-arid and arid area with low rainfall and uneven spatial and temporal distribution,which affects the growth and yield of potato plants.Deficit irrigation is an irrigation model based on the physiological characteristics of crops,the yield of crops is not reduced or even increased without being meet with the water demand,and the potential of crops for efficient use of water can be fully exploited.The root group of potato is mainly distributed in the soil layer within 30 cm,which has low absorption and utilization of soil moisture and is considered to be a water sensit ive crop.Therefore,the effects of growth,physiological characteristics,yield and tuber quality of different potato plants under water deficit were studied and the changes of rhizosphere soil moisture,water use efficiency and irrigation efficiency were explored,which could provide a theoretical basis for efficient potato production in arid areas.The experiment was carried out in the Agricultural Science Research Institute of Dingxi C ity of Gansu Province in 2017.Under drip irrigation condition with rainproof shelter in field,the different varieties(clones)of potato were used as materials,and the average annual rainfall of the northwest area and the experimental area was determined in the tuber formation and maturity stage.Four water treatments were set at the seedling stage,divided into normal irrigation(T1),mild(T2),moderate(T3),severe(T4).Five water treatments were set up.The annual average rainfall value of the reference test area was divided into normal irrigation(A),and the value of the graded deficit irrigation was divided into mild(B),moderate(C),severe(D)and extremely sever(E)by level-adjusting deficit irrigation to study the effects of irrigation time and irrigation amounts on plant growth(plant height,stem diameter,leaf area),biomass accumulation and distribution,leaf relative water content,photosynthetic,physiological characteristics,yield and composition factors,water use and quality.The research results obtained are as follows:1.Deficit irrigation of’Atlantic’and’Q ingshu 9’during tuber formation to maturity stage:with increasing water deficit,plant height,stem diameter,leaf area,dry matter accumulation,leaf relative water content,leaf SPAD value and the photosynthetic parameters of the leaves o f’Atlantic’showed a downward trend.The above indicators of’Q ingshu 9’showed a decreasing trend at first and then increasing.Under B treatment(mild deficit irrigation),each index showed the highest value.The content of proline and SOD in two variety leaves decreased at first and then increased with the decrease of soil water content.Both proline content and SOD activity decreased at first and then increased with the decrease of soil water content.2.In the tuber formation period to maturity stage,the yield per plant and the rate of large potato of’Atlantic’were significantly lower than the normal irrigation(P<0.05).Under the mild deficit irrigation,the rate of large potato of’Q ingshu 9’was lower than the normal irrigation(P<0.05),the potato number of per plant,yield per plant and hectare yield were significantly higher than normal irrigation(P<0.05),and water use efficiency(WUE)and irrigation efficiency(IE)were 152.62kg/(hm~2·mm)and130.70%,respectively.Under the mild deficit irrigation,the yield per plant and the yield per hectare have a compensatory effect,which is 22.79%and 11.71%higher than the normal irrigation,the WUE is increased by 41.48%,IE increased by 60.05%and drought resistance coefficient is 1.12.3.Under potato seedling deficit irrigation,plant height,stem diameter,leaf area,leaf chlorophyll content and leaf photosynthetic characteristics of 4 potato cultivars(Atlantic,Q ingshu 9,CIP388615.22(referred as 99),CIP 304371.67(referred as 122))showed a downward trend with the increase of water deficit.The SOD activity and proline content of leaves increased with the increase of deficit.The effect of severe water deficit on potato plants was significantly greater than that of mild water deficits.Re-watering after water deficit was relieved,the indexes of four potato varieties(lines)(plant height,leaf area,photosynthetic characteristics)were restored to varying degrees,and the’122’with strong drought resistance showed obvious advantages of recovering after drought stress with the growth ability(plant height,leaf area,photosynthetic characteristics)is stronger of recovering period;the’Atlantic’is greatly affected by drought stress and unable to return to normal growth during recovering period;The’Q ingshu 9’and’99’were also affected by drought stress and their ability to return to normal growth after drought is between the’122’and’Atlantic’.4.Under mild water deficit in seedling stage,the tuber number per plant,yield per plant,hectare yield and commercial potato rate in’99’and’122’were not significantly different compared with the control,while the above indicators of’Qingshu 9’reached the highest value,whereas,the yield per plant and the hectare yield were significantly lower among other treatments under severe water deficit.In terms of tuber quality,the dry matter and starch content in tubers of’Atlantic’were the highest under normal irrigation,which were highest in the other three cultivars under mild deficits.The mild water deficit in the seedling stage is beneficial to improve of tuber quality.5.The potato yield of drought-tolerant varieties increased under mild water deficits during seedling stage and tuber formation to maturity stage,while the potato yield of drought-sensitive varieties only increased when suffered mild water deficit in the seedling stage,and decreased dramatically under moderate and severe water deficit.It indicated that the water deficit in tuber formation stage to maturity stage had greater impact on yield than that in seedling stage,and the compensatory effect of rewatering and drought-resistant varieties in seedling period under mild water deficit was greater than that of drought-sensitive varieties.Under the moderate-to-severe water deficit stress,the decline range in production of the four varieties(lines)was’Atlantic’>’99’>’Qingshu 9’>’122’.In conclusion,the exuberant aboveground growth of drought-tolerant cultivarQingshu 9‘,99‘and122‘can be inhibited under mild deficit irrigation,which is conducive to light utilization efficiency,dry matter accumulation,tuber formation and expansion,on the contrary,drought-sensitive cultivarAtlantic‘should by supplied with sufficient water during the growth period.