Effects Of Reduced Irrigation On Broccoli Growth And Soil Water Distribution In Bashang Open Field

In order to solve the problems of low water use efficiency and waste of irrigation water resources of broccoli planted in dam area of Zhangjiakou,the experimental materials were selected from the local main broccoli variety’Cold-resistant Excellent’,and the single factor randomized block design was adopted.Six treatments were set up according to the irrigation quota,and each treatment was repeated three times,（W1treatment was 100%of field capacity,W2 treatment was 90%of field capacity,W3treatment was 80%of field capacity,W4 treatment was 70%of field capacity,W5treatment was 60%of field capacity,W6 treatment was 50%of field capacity）he effects of different water-saving irrigation amounts on the growth index,root configuration,quality,yield and photosynthetic characteristics of broccoli were systematically studied,and the principal component analysis and comprehensive evaluation of these indexes were carried out.It provides a reliable theoretical basis and scientific basis for ensuring economic development for open field broccoli water-saving irrigation planting in dam area of Zhangjiakou.The main results are as follows:（1）The effects of different water-saving irrigation amounts on the growth indexes of broccoli at different growth stages were significantly different.The growth indexes of each treatment at different growth stages of broccoli were analyzed by principal component analysis.The comprehensive evaluation of the growth indexes of broccoli at rosette stage was ranked as W6>W2>W1>W5>W4>W3.The growth indexes of W6 treatment（50%field capacity）were the best.The comprehensive evaluation of the growth indexes of broccoli during the expansion period of broccoli was W3>W2>W4>W5>W1>W6,and the growth indexes of W3 treatment（80%field capacity）were the best.The comprehensive evaluation of the growth indexes of broccoli in the harvest period was W2>W4>W3>W1>W5>W6,and the growth indexes of W2 treatment（90%field capacity）were better.Therefore,the irrigation standard of broccoli in rosette stage was 50%field water yield（the irrigation amount in this experiment was 288.61m³/hm²）,and the growth traits of each growth index were the best.The growth traits of each growth index were the best when the irrigation standard was 80%field capacity（the irrigation amount in this experiment was 589.70 m³/hm²）.The irrigation standard of broccoli harvest period was 90%field capacity（irrigation amount 775.15 m³/hm² in this experiment）,and the growth index of each treatment was the best.（2）Through the analysis of the root configuration of broccoli during the harvest period,different water-saving irrigation amounts had a significant effect on the root configuration of broccoli.With the increase of irrigation amount,it showed a trend of decreasing first and then increasing.The root length,root surface area and root tip number of W1 treatment were significantly higher than other treatments.The principal component analysis of the root configuration of each treatment showed that the root development of W1 treatment（100%field water holding capacity）was the best,with a total root length of 1871.39 cm,a root diameter of 1.29 cm,a root surface area of 1180.61 cm²,a root volume of 247.23 m³,and a root tip number of 3595.33.Therefore,the root development was the best when the irrigation standard of broccoli was 100%field capacity（the irrigation amount in this experiment was 935.15 m³/hm²）.（3）There were significant differences in the quality and yield of broccoli between different water-saving irrigation amounts.The chlorophyll and yield of W5 treatment were significantly higher than those of other treatments.The principal component method was used to comprehensively analyze the quality,yield and other indicators.The comprehensive evaluation of each growth was ranked as W5>W4>W6>W3>W2>W1.Therefore,the irrigation standard of broccoli in the harvest period is 60%field capacity（the irrigation amount in this experiment is 306.67 m³/hm²）.The quality and yield are the best.The soluble sugar content was 8.4,the chlorophyll content was 79.89%,the biomass was 26117.52 kg/hm²,the total commodity yield was 12687.27 kg/hm²,and the total yield was 20807.96 kg/hm².（4）There were significant differences in the effects of different water-saving irrigation amounts on the photosynthetic characteristics of broccoli.The stomatal conductance and intercellular carbon dioxide of W3 treatment were significantly different from other treatments.The photosynthetic characteristics of each treatment were comprehensively evaluated.The results showed that the photosynthetic index was the best when the irrigation standard of broccoli was 80%field capacity（the irrigation amount in this experiment was 589.70 m³/hm²）.Photosynthetic rate was 26.43 mol m^-2s^-1,stomatal conductance was 0.8 mol H₂O·m.s^-1,intercellular carbon dioxide was273.73μL.L^-1,transpiration rate was 6.31 mmol m^-2s^-1..（5）There was no significant difference in soil relative water content in different soil layers of broccoli fields under different water-saving irrigation amounts.The overall trend of each treatment was that the soil relative water content in the 0～50 cm soil layer maintained a gradual upward trend,and the soil water content in the 50～80 cm soil layer gradually decreased.The soil relative water content in the 50 cm soil layer of each treatment was the largest.（6）The analysis of water-saving irrigation benefit of each treatment is as follows:W1 treatment has the most irrigation amount,the least water-saving amount and water-saving economic benefit.W6 treatment has the least irrigation amount of 288.61 m³/hm²,the most water-saving amount of 646.55 m³/hm²,and the highest water-saving economic benefit of 387.93 yuan/hm².（7）Considering comprehensively,under the condition of the same amount of fertilizer,the growth traits were the best when the irrigation standard was 50%field capacity（the irrigation amount in this experiment was 288.61 m³/hm²）.The growth traits and photosynthetic characteristics of broccoli were the best when the irrigation amount was 80%field capacity（the irrigation amount in this experiment was 589.70 m³/hm²）.The growth traits of broccoli were the best when the irrigation standard was 90%field capacity（the irrigation amount in this experiment was 775.15 m³/hm²）,the quality of broccoli was the best when the irrigation standard was 60%field capacity（the irrigation amount in this experiment was 306.67 m³/hm²）,the biological yield of broccoli was the highest when the irrigation standard was 50%field capacity（the irrigation amount in this experiment was 288.61 m³/hm²）,the root system was the best and the economic yield was the highest when the irrigation standard was 100%field capacity（the irrigation amount in this experiment was 935.15 m³/hm²）.