| The field test was conducted in the western Loess Plateau, the treatments including conventional tillage(T) ,surface seeding in the stubble mulched ditch with plastic film mulched ridge (PDSS),shallow seeding in the stubble mulched ditch with plastic film mulched ridge (PDSSH),surface seeding on ridge with stubble(RSS),surface seeding in flatten culture with stubble (FSS) and surface seeding in the stubble mulched ditch without plastic film mulched ridge (DSS).Through analysis of agronomic characteristics,economic characters,dry matter accumulation and distribution,soil water,soil temperature and soil characters ,the effects of conservation tillages on yield formation of potato were preliminarily studied,comes to the following conclusions:1.No-tillage with stubble retention could increase water storage in 0～80 cm soil layer, especially in 0～30 cm soil layer in the poor raining year. Soil water at 0～30cm profile of no-tillage was respectively increased 35～89%,20～69%,54～76% and 12～29% at pro-sowing,emergence stage,squaring stage and tuber expansion period. Soil water at 30～80cm profile of no-tillage was respectively increased 9～14%,19～33%,6～28% and 2～44% of T at seedling stage,squaring stage,flowering stage and tuber expansion period.2. No-tillage with stubble retention FSS and PDSSH could decrease soil accumulated temperature as compared with conventional tillage, and also decreased the daily temperature of layer of potato development at 14:00 in sunny. The accumulated temperature of RSS,PDSS and DSS were 1545.63～1875.56℃; The accumulated temperature of FSS was 1564.84～1745.96℃; The accumulated temperature of PDSSH was 1547.35～1691.01℃; The T accumulated temperature was 1632.48～1808.42℃.The temperature of layer of potato development at 14:00 in sunny,FSS was 27～29℃,PDSSH was 21～28.5℃, they were lower than T, the T temperature was 27～32℃,therefore,it reduced the harm to potato development. No-tillage with stubble retention could increase the content of total N,organic matter,available K and available P in 0～10cm soil layer,but didn't achieve significant difference.3. No-tillage with stubble retention was harm to root development,plant development and dry matter accumulation at earlier growth stage,but accelerated grow at later growth stage. The whole plant dry matter of each treatment achieved significant difference,T was the best,the difference reduced with the passage of time. The dry matter accumulation no-tillage with stubble retention exceed T at mature stage;The tendcy of plant heigh,stem diameter, plant number of leaves,branch number above-ground and stolon number was same.At flowering stage,the plant type of T was most vertical,no-tillage with stubble retention was half-vine and vine,it showed that the growth of conservation tillage was superior than T.4. The distribution of dry matter in tuber of conservation tillage was less than T,but dry matter absolute quanlity was FSS>PDSSH>DSS>PDSS>T>RSS ,because of emergence rate . At mature stage, the distribution of dry matter in tuber of T was the heightest,reached 81.26%,the order was followed:T>RSS>FSS>DSS>PDSS>PDSSH, each treatment achieved very significant difference.5.The green tuber rate,small tuber rate,potato weight per plant and potato number per plant were higher higher than T,but the big tuber rate was lower than T. Big tuber rate: T>RSS>FSS>PDSS>PDSSH>DSS,middle tuber rate: FSS>T>RSS>DSS>PDSSH>PDSS , small tuber rate: PDSS>PDSSH>DSS>RSS>FSS>T,but they got no markedness. The green potato rate of no-tillage was higher than T,the treatment of 5cm shallow seeding in the stubble mulched ditch could reduced the green tuber rate. Potato number per plant: PDSS >PDSSH>DSS>FSS>RSS>T, potato number of PDSS,PDSSH and DSS were most , respectively increased 45.57%,43.04% and 26.58% of T. Each treatment got no markedness. Potato weight per plant: RSS>DSS>PDSSH>PDSS>FSS>T,each treatment got no markedness.6. No-tillage with stubble retention could improve the emergence rate and yield,except RSS,but emergence was late and no order. Emergence rate: FSS>PDSSH >DSS>PDSS>T >RSS, FSS,PDSSH,DSS and PDSS respectively increased 20.84%,16.93%,15.83% and 13.35%, FSS,PDSSH got markedness as compared with T.Yield: FSS>PDSSH>DSS>PDSS>T>RSS, FSS,PDSSH got markedness as compared with T,the yield of FSS and PDSSH respectively was 27469.28kg/hm2 and 25812.90kg/hm2,increased 30.05% and 22.20% of T.It showed that conservation tillage could increase the yield on the Loess Plateau,especially in the poor raining year.
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