| The Yellow River Diversion Irrigation District in Gansu is a typical ecological fragile area in Northwest of China.The agriculture in this area is dominated by traditional irrigation,the planting mode is single,and the utilization efficiency of water and soil resources is low.Therefore,it is imperative to adopt high-efficiency water-saving irrigation measures.Forest-grass intercropping system can reduce ineffective evaporation,improve water and soil utilization,increase economic income,and is widely used.At the same time,because forest and forage share resources,competition will inevitably be caused,and water is the most important factor in competition.Due to the increase of the intercropping period,the competition between the two groups is different,and the response to different water-saving regulation is also different.Therefore,this experiment was conducted at the irrigation experimental station of Jingtaichuan Electric Power Irrigation Administration Bureau in Gansu Province.The Lycium barbarum-Sainfoin intercropping system with different intercropping years(1,2,3,4 years)and Lycium barbarum monoculture system were selected as the research objects.Setting 3 irrigation levels(full irrigation:75%～85%θ_f(F),slight deficit:65%～75%θ_f(S),moderate deficit:55%～65%θ_f(M)).The effects of water-saving regulation on crop growth indicators,photosynthetic characteristics,quality and water use efficiency are analyzed.The result shows that:(1)Under the same mode,plant height,east-west and north-south crown width decreased with the decrease of irrigation level.When the intercropping period was 1,the growth vigor of wolfberry was the best(plant height:149.13 cm,east-west crown width:151.66 cm,north-south crown width:140.17 cm),followed by intercropping time was 2,but there was no significant difference between intercropping time 2 and monoculture wolfberry.The plant height increased with the increase of intercropping years and decreased with the decrease of irrigation level.The stem-leaf ratio increased with the increase of intercropping years,and decreased with the increase of stubble.When the intercropping period was 1,the stem-leaf ratio was the smallest,but the difference was not significant with the intercropping period of 2.When the intercropping period was 2,the stem-leaf ratio was the smallest under slight deficit irrigation(1.59),which was 3.05%and 1.24%lower than that under full irrigation and moderate deficit respectively.(2)Chlorophyll content of intercropping was 1.86%～8.77%higher than monoculture.When the intercropping years were 1,2 and 3,the chlorophyll content of wolfberry increased at first and then decreased with the decrease of irrigation level.When the intercropping years was 4,the irrigation level had no significant effect on the chlorophyll content of wolfberry.The chlorophyll content of monoculture wolfberry decreased with the decrease of irrigation level.Chlorophyll decreased with the decrease of irrigation level,and gradually increased with the increase of intercropping years.The diurnal variation of Pn of monoculture was more obvious than that of intercropping 1 year and 2 years,and the diurnal variation of Pn of intercropping 3 and 4 showed a single peak curve.The order of diurnal average net photosynthetic rate of L.barbarum was as follows:intercropping years is 1>intercropping years is 2>L.barbarum monoculture>intercropping years is 4>intercropping years is 3.The order of daily average transpiration rate of Lycium barbarum is monoculture>intercropping years is 2>intercropping years is 1>intercropping years is 3>intercropping years is 4.The diurnal variation of net photosynthetic rate of Sainfoin was dominated by M-type double peaks,and the first peak value was significantly higher than the second peak value.When the intercropping year was 4,it showed a single peak trend.The daily mean values of net photosynthetic rate and transpiration rate of Sainfoin increased at first and then decreased with the extension of intercropping years.(3)The yield of Chinese wolfberry decreased with the decrease of irrigation level,but there was no significant difference between intercropping years 1 and 2 and monoculture under sufficient and mild deficit irrigation levels.The order of wolfberry yield was monoculture>intercropping period is 1>intercropping period is 2>intercropping period is 3>intercropping period is 4.The yield of Leguminosae decreased with the decrease of irrigation level,and increased at first and then decreased with the extension of intercropping years.Water use efficiency increased first and then decreased with the decrease of irrigation level.The order of water use efficiency of each model was as follows:intercropping period is 2>intercropping period is 4>intercropping period is 3>intercropping period is 1>wolfberry monoculture.Irrigation water use efficiency increased with the decrease of irrigation level.When the intercropping period is 2,the slight deficit irrigation had higher water use efficiency(27.69 kg/(mm·hm~2))and irrigation use efficiency(39.24kg/(mm·hm~2)).(4)Reducing irrigation level can increase the content of total sugar and polysaccharide,but limit the accumulation of flavonoids.However,too high and too low irrigation levels are not conducive to the accumulation of total polyphenols.The order of total sugar content of Lycium barbarum L.was that intercropping period is 1>intercropping period is 2>Lycium barbarum L.monoculture>intercropping period is 4>intercropping period is 3.When the intercropping period was 2,the contents of polysaccharide,flavonoids and total polyphenols in Lycium barbarum were the highest,which were 4.49%,1.16%and 1.53mg/g,respectively.The acid detergent fiber decreased at first and then increased with the decrease of irrigation level and the extension of intercropping years.The crude protein content increased with the decrease of irrigation level,and first increased and then decreased with the increase of intercropping years.The relative forage value of Legume grass first increased and then decreased with the decrease of irrigation level.When the intercropping period was 2,the quality of red bean grass was better.Among them,the relative feed value of red bean grass under mild deficit irrigation level was the highest,which was 159.12,with higher crude protein content(15.65%)and lower fiber content(ADF:30.06%,NDF:38.27%).(5)Comprehensive quality(total sugar,polysaccharide,flavonoids and total polyphenols of wolfberry,neutral detergent fiber,acid detergent fiber and crude protein content of red bean grass),yield and water use efficiency were evaluated based on grey correlation degree.It was concluded that the irrigation effect of slight water deficit was the best when wolfberry-Sainfoin intercropping for 2 years. |
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