| Lhasa is located in Lhasa river valley belt,the main farming area of Tibet,oat is one of the artificial forage widely planted in this area in recent years.The growth of oat in this area mostly depends on rainfall and ground irrigation,but due to the backward construction of local water conservancy infrastructure,thin soil layer and uneven terrain,the yield of oat is low and the utilization efficiency of irrigation water is low.Sprinkler irrigation has the advantages of high automation,water saving and yield increasing,and is an important and efficient water-saving irrigation technology gradually introduced and promoted in Lhasa.At high altitudes unique natural climate conditions,the irrigation water in the process of transport to the field of radiation will affect its has not yet been determined,sprinkler irrigation technical parameters by mainland value needs to be confirmed in the Lhasa area irrigation oats under the condition of water consumption,irrigation system,and so on the present situation of the unknown,linzhou county in Lhasa to carry out the related research,the main results were as follows:(1)Based on the data collection,analysis and field measurement of the sprinkler irrigation project in Linzhou County,Lhasa city,the economic benefits of four sprinkler irrigation types were obtained in the order of fixed sprinkler irrigation>semi-fixed sprinkler irrigation>clockwise sprinkler irrigation>coil-disk sprinkler irrigation,which increased 5078,4242,4009 and 3414 RMB/hm~2·year respectively over the traditional surface irrigation method.Compared with surface irrigation,clockwise sprinkler irrigation,semi-fixed sprinkler irrigation,coil sprinkler irrigation and fixed sprinkler irrigation save water by 50.96%,47.94%and 43.60%,respectively.(2)The atomization index W_h,sprinkler intensity P,uniformity C_u and evaporation drift lossλof semi-fixed pipe sprinkler system(rock-arm sprinkler PY-5022)in Lhasa were measured in the field,and the correlation analysis was carried out with typical meteorological factors.The results showed that the uniformity C_u was negatively correlated with temperature,radiation and wind speed.The evaporation drift lossλis positively correlated with temperature,radiation and wind speed.The influencing factors of C_u:T>W>Le(R~2=0.536,0.511,0.256).λ:W>Le>T(R~2=0.532,0.300,0.254).The evaporation drift loss increased by 15%-23%and the uniformity of sprinkler irrigation decreased by 12%-19%due to radiation in Lhasa.It is recommended that the working pressure of rocker sprinkler irrigation system in Lhasa should be controlled at 260-280kpa,and the operation should be carried out under the environment of 0-2m/s wind speed,-2MJ/m~2 net radiation below 0 and 12-14℃temperature.At this time,the atomization index is 2500-4000 and the intensity of sprinkler irrigation is 7.04-9.67mm/h.(3)Based on the field measured data,according to the water balance method,the water consumption of oat during the whole growth period of sprinkler irrigation is473.4mm,in which the water demand of oat during jointing-heading period is 197.91mm,the water consumption modulus is 42.05%,and the water consumption intensity is5.65mm/d.It can be seen that the jointing-heading period is the key period of water demand of oat.Both water consumption modulus and water consumption intensity are greater than other periods.This period belongs to the mature period of oats,and the growth period is long.At this time,the grain of crops is gradually saturated,and the stem reaches the strongest state,so the water consumption modulus and water consumption intensity are high.Ensuring the water demand of oat during the critical period of water demand can increase yield appropriately.(4)Adequate irrigation systems and irrigation systems with the highest water productivity are particularly needed in Lhasa because of its abundant water resources and low pasture production.The irrigation system of oat in Lhasa area was obtained by field control experiment and CROPWAT model optimization.If the irrigation system with maximum yield was pursued,the total amount of spraying irrigation was 133.9mm for nine times,including one time before seedling emergence(14.2mm),two times at seedling-tillering stage(18.3mm),three times at tiller-jointing stage(43.2mm),two times at joining-heading stage(37.0mm),and one time at heading-cutting stage(22.2mm).If the irrigation system with the highest water productivity is pursued,eight sprinkler irrigation can be carried out,the total quota of sprinkler irrigation is 119.9mm,at this time,the yield almost does not decrease,respectively,one time before seedling emergence(14.2mm),two times at seedling-tillering stage(19mm),three times at tiller-jointing stage(27.6mm),two times at jointing-heading stage(37.0mm),Heading-cutting stage once(22.1mm). |
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