| In view of the low utilization rate of nitrogen fertilizer caused by unreasonable fertilization measures in potato production in Inner Mongolia and the increasing waste of resources and environmental pollution caused by nitrate leaching.In this experiment,potatoes were studied under drip irrigation under mulch.Under the condition of 315 kg/hm2 of total nitrogen,13 treatments were set up at different nitrogen topdressing stages(1,2,3,4)and times(A,B,C)on the basis of uniform base application of 43%nitrogen fertilizer.The growth and development,photosynthetic characteristics,yield formation,nitrogen transport,nitrogen use efficiency and economic benefits of potatoes with drip irrigation under mulch were systematically studied,and the temporal and spatial changes of nitrate nitrogen content in 0-80cm soil were also studied.The optimum nitrogen topdressing period and times were found out,in order to provide theoretical basis for nitrogen fertilizer management for potato production under drip irrigation under mulch.The main conclusions are as follows:(1)The application of nitrogen fertilizer in different stages from tuber formation to mid-expansion was beneficial to the increase of plant height,stem diameter,LAI and the maintenance of relatively high SPAD value and net photosynthetic rate of leaves in late growth stage,and to the enrichment of sufficient source-support pools.(2)Submulch drip irrigation of potatoes from tuber formation stage to the end of tuber enlargement was beneficial to the accumulation of dry matter in tubers.The dry matter accumulation of tubers treated with nitrogen topdressing for 1,2 and 3 times in harvest period was increased by 107.14%-146.23%,146.71%-182.48%,155.5%-171.87%compared with CK.Nitrogen topdressing for 2 and 3 times increased by 16.71%and 15.97%compared with that for 1 time.Among them,treatment B3 was the highest,followed by treatment C3.(3)Nitrogen accumulation in potato tubers could be significantly increased by applying nitrogen fertilizer in different stages from tuber formation to the end of tuber expansion.At harvest time,nitrogen accumulation in tubers increased by 136.83%-185.96%,156%-214.35%,184.25%-213.75%after 1,2 and 3 topdressing treatments,compared with CK,and increased by 18.53%and 22.82%after 2 and 3 topdressing treatments.Nitrogen fertilizer use efficiency of fractional topdressing was significantly higher than that of single topdressing.The recovery efficiency of nitrogen fertilizer,partial productivity of nitrogen fertilizer and agronomic efficiency of nitrogen fertilizer in B3 treatment were the highest,which were 51.32%,149.14kg.kg-1 and 76.57kg.kg-1.(4)The accumulation of nitrate nitrogen in 0-80 cm soil layer was increased during the delayed nitrogen topdressing period,but the residual nitrate nitrogen in each soil layer decreased with the increase of nitrogen application times.The depth of nitrate accumulation increased with the delay of nitrogen application period,and the nitrate accumulation in 60-80 cm soil layers was significantly lower than that in 1 or 2 nitrogen topdressing treatments.(5)The key to high yield is timely and sequential Topdressing of nitrogen fertilizer.The average yields of 1,2 and 3 nitrogen topdressing treatments were 35.59 t/hm2,42.98 t/hm2 and 41.93 t/hm2.The yields of 2 and 3 nitrogen topdressing treatments were 20.75%and 17.8%higher than that of 1 nitrogen topdressing treatment.The difference was significant.Among the 1,2 and 3 nitrogen topdressing treatments,the combination treatments of A3,B3 and C3 were the highest,which were 38.5 t/hm2,46.98 t/hm2 and 44.55 t/hm2.Under this experiment condition,the potato nitrogen fertilizer management with drip irrigation under mulch was based on 43%nitrogen application,and the other nitrogen was best applied twice at the tuber formation+the middle of tuber expansion. |
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