基于液流计估测蒸腾分析覆膜滴灌玉米节水增产机理

深入了解覆膜滴灌下冠层辐射传输和能量分配情况，确定土壤蒸发和作物蒸腾之间的定量区分关系是合理灌溉和提高水分利用效率的重要研究内容。该研究在东北膜下滴灌地区开展连续2 a田间试验，测定了覆膜（M）和不覆膜（NM）玉米田的冠层辐射、田间土壤蒸发和作物蒸腾、作物生长和产量。结果表明：覆膜使冠层上方净辐射降低7.7%，从而减少了蒸发蒸腾可供能量，冠层下方净辐射降低34.0%，减少了土壤蒸发可供能量，冠层净辐射吸收量增加14.0% 用于作物蒸腾；覆膜能小幅度降低蒸发蒸腾总量3.9%～5.2%，而对其在土壤蒸发和作物蒸腾之间的分配影响显著，覆膜处理土壤蒸发占蒸发蒸腾总量的比例为12.5%～14.5%，而不覆膜处理该比例高达21.7%～25.0%；覆膜处理提高了成熟期玉米株高、地表20 cm高度处茎粗、生物量和最大叶面积，最终使产量提高5.9%～8.8%，水分利用效率提高12.0%～13.1%。综上所述，覆膜通过改变冠层辐射能量分配降低了玉米田蒸发蒸腾总量，提高了玉米产量和水分利用效率。

Analysis of water saving and yield increasing mechanism in maize field with drip irrigation under film mulching based on transpiration estimated by sap flow meter

Abstract: Determine evapotranspiration (ET) and its components is important for us to understand the influence of mulching on filed water consumption, to develop precision irrigation scheduling and to improve water use efficiency in the field. In this study, the net radiation, field soil evaporation and crop transpiration, crop growth and yield of film mulching (M) and non-mulching (NM) maize fields were measured in a continuous 2 years field experiment in the drip irrigation with mulching area of ??Northeast China. Net radiation was measured by two net radiometers in the center of every representative plot of the M and NM treatments at height of 50 cm above the canopy adjusted with the increase of plant height and 30 cm above ground. Soil evaporation was measured by micro-lysimeters made from polyvinyl chloride (PVC) tubes and it was weighed every day. Transpiration during the middle and late growth period was measured and scaled up from the sap flow rates. Transpiration of the whole growth period were calculated the by using the dual crop coefficient method with the adjusted medium-term basal crop coefficient from the FAO-56 manual. The medium-term basal crop coefficient were adjusted with the measured transpiration. The results showed that: The net radiation above the canopy of M treatment reduced by 7.7%, i.e. the energy available for evapotranspiration reduced. The net radiation under the canopy of M treatment reduced by 34.0%, i.e. the energy available for soil evaporation (Es) reduced. However, the net radiation absorption by the canopy of M treatment increased by 14.0% for crop transpiration (Tr). The film mulching could reduce the total amounts of evapotranspiration by 3.9%(5.2%. ET of M was 471.3mm in 2014, which was 5.2% lower than that of NM treatment (497.4 mm). In 2015, ET of M was 413.4 mm, 3.9% lower than that of NM treatment (430.0 mm). The film mulching had a significant effect on the water consumption distribution between Es and Tr. Total Esof the whole growth stage for M and NM treatments were 58.8 and 108.8 mm in 2014, 60.0 and 107.6 mm in 2015. Plastic mulching decreased Es by 44.7% and increased Tr by 7.8% in this area for the two years, comparing to those of NM treatments.The ratios of Es to ET in 2014 and 2015 were 12.5%(14.5% for the M treatment, and which were up to 21.7%(25.0% for the NM treatment. The ratios of Tr to ET were 85.5%(87.5% and 75%(78.3% for M and NM treatments, respectively. The plant height of maize, the stem diameter at 20 cm height above the ground, biomass at the maturity stage and the maximum leaf area index of treatment M were significantly higher than those of treatment NM by 7.1%, 5.8%, 4.8% and 1.7% in 2014 and 5.4%, 8.8%, 6.9% and 2.2% in 2015. The yield of M treatment increased by 5.9%(8.8%, and water use efficiency increased by 12.0%(13.1%. In summary, the film mulching reduced the total amount of ET in maize field by changing the canopy radiation energy distribution, and finally enhanced the plant growth, increased grain yield and water use efficiency in maize field with drip irrigation in this area.