| Farmland shelterbelt plays an important role in maintaining agricultural production,achieving stable yield and increasing yield by improving the microclimate of farmland and reducing the impact of agricultural disasters.In this study,farmland shelterbelts with different structures in Qingtongxia City were taken as the research object.By observing air temperature and humidity,soil water content,photosynthetically active radiation(PAR),net photosynthetic rate(Pn),maize yield and other indicators,the microclimate effects of shelterbelt at different growth stages of maize were studied,the effects of shelterbelt at different growth stages of maize on the photosynthetic characteristics of maize were analyzed,and the effects on maize yield were determined.The results should provide guidance for the construction and renewal of farmland shelterbelts in Ningxia.The main conclusions are as follows:(1)The soil water content of farmland at different growth stages of Maize showed an obvious increasing trend with the increase of distance from the shelterbelt.Compared with 2H,the soil water content in the range of 0.3H(H is the height of the tree)of shelterbelt with different structure at jointing stage and filling stage decreased by more than 10%,and the soil water content in the range of 0.3H at heading stage decreased by more than 7%.Farmland shelterbelt had the greatest influence on soil water content in 0-40 cm layer.The degree of influence of shelterbelt with different structure on soil water content was three rows>double rows>single row.The effect of shelterbelt at jointing stage and heading stage on soil water content on the east and west sides was greater than that on the north and south sides.(2)The air temperature of farmland at different growth stages of Maize increased with the increase of the distance from the shelterbelt,and the air humidity at 1H and 2H had little difference.Farmland shelterbelt had the greatest impact on air temperature at heading stage.The air humidity at heading stage and filling stage increased with the increase of distance from shelterbelt,but showed the opposite trend at jointing stage.The three-row farmland shelterbelt has the great influence on the air temperature and humidity of farmland.Farmland shelterbelt at different growth stages have the greater impact on air temperature and humidity on the north side.(3)The photosynthetically active radiation(PAR)and net photosynthetic rate intercepted by maize leaves at different growth stages increased with the increase of distance from the shelterbelt.At jointing stage,PAR and Pn were lower in the range of 0.3H on the north and south sides,and 0.5H on the east and west sides.At heading stage,PAR and Pn were lower in the range of 0.5H on the north and 0.1H on the south,and 0.5H on the east and west sides of the shelterbelt.PAR and Pn were lower in the range of 0.3H on the north and south sides of the shelterbelt,and 0.5H on the east and west sides during the filling stage.The three-row shelterbelt had the greatest influence on the photosynthetic characteristics of maize,and the influence on the east and west sides was stronger than that on the north and south sides.(4)The height and ground diameter of maize at different growth stages increased with the increase of distance from shelterbelt.At jointing stage,the shelterbelt had the great influence on the height and ground diameter in the range of 0.5H,however it had a great influence on the height and ground diameter in the range of 0.3H at the heading stage and filling stage.The degree of influence of shelterbelt with different structure on height and ground diameter of maize:three-row shelterbelt>double-row shelterbelt>single-row shelterbelt.The influence of shelterbelt on the east and west sides is higher than that on the south and north sides.(5)The yield of maize increased with the increase of distance from the shelterbelt.The severe yield reduction ranges of three-row,double-row and single-row shelterbelt were 0.1H-0.5H,0.1H-0.5H and 0.1H-0.3H,respectively.The general yield reduction range was 0.51-1H,0.5H-1.1H,0.3H-0.8H;the single-row shelterbelt had the least effect on yield,and the three-row shelterbelt had the greatest effect on yield.The influence range of shelterbelt with different structure on yield of maize was different in different directions.The influence of shelterbelt on yield of maize on the east and west sides was higher than that on the north and south sides.(6)There was a significant correlation between the yield of maize and soil water content,air temperature(Ta),air humidity(RH),PAR and Pn,and the correlation with soil water content was the strongest.Compared between the different growth stages,the correlation between yield and different factors at heading stage and filling stage was stronger. |
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