| In order to investigate the effect of phosphorus application depth on the root growth and yield of reclaimed cropland buckwheat under water stress,Then provide technical support and theoretical basis for tartary buckwheat dryland planting management measures.the "Heifeng No.1" buckwheat variety was selected as the test material,a combination of soil column experiment and field experiment were conducted: i)The soil column experiment was conducted using a split-plot design with soil water conditions as the main plot,and phosphorus application depths as the subplot.The soil water conditions included W1(normal water supply,soil water content was 65-75% of drained upper limit),W2(moderate drought,soil water content was 45-55% of drained upper limit)and W3(severe drought,soil water content was 35-45% of drained upper limit).Phosphorus were applied at different depths from the ground surface: 10 cm(P10),20 cm(P20),30cm(P30)and 10-30cm(P-all).ii)The field experiment was conducted using a single-factor design with four phosphorus application depths without irrigation during the whole growth period.The phosphorus application treatment were the same as soil column experiment.The main findings are as follows:i)The soil column experiment:With the increasing of drought stress,the value of various indicators of buckwheat shoot and underground were all decreased in the seedling period.Compared with W1 treatment,buckwheat plant height,stem thickness and leaf area of W3 decreased by 17.2%,18.03% and23.17%,respectively,and buckwheat total root length,total root surface area and total root volume of W3 decreased by 16.97%,20.39% and 17.39%,respectively.Through the application of phosphorus fertilizer at 10 cm,buckwheat roots can be promoted down to deep,improve the efficiency of water and fertilizer utilization,so that the plant absorbs more water and fertilizer,and ultimately promote the growth of buckwheat shoot and root.In the seedling period,soil water and phosphorus application depth significantly affected the dry matter accumulation of buckwheat,the more severe the water stress,the more significant the decline in dry matter accumulation of shoot and root of buckwheat,compared with W1 treatment,the above-ground dry matter and root dry matter of W3 treatment decreased by 39.16%,28.60%.With the phosphorus fertilizer application at 10 cm,it can alleviate the damage caused by water stress,which in turn promoted the growth of buckwheat and ultimately increased the dry matter accumulation of buckwheat.In the seedling period,compared with W1 treatment,the average root length of W2 and W3 treatment in the 0-10 cm and 10-20 cm soil layers decreased by 30.18% and 27.55%,41.83% and 41.02%,respectively,and the root dry matter of W2 and W3 treatment decreased by 36.62% and 33.61%,49.72% and 48.11%,respectively;the average root length of W2 and W3 treatment in the 20-30 cm and 30-45 cm soil layer increased by 33.53% and 42.52%,31.74% and 50.95%,respectively,and the root dry matter of W2 and W3 treatment in the20-30 cm and 30-45 cm soil layer increased by 13.70% and 26.84%,5.85% and 28.64%,respectively.Deep phosphorus application promotes the growth of the soil root system in the phosphorus application layer.Compared with the P-all treatment,the P10 treatment increased the root length in the 10-20 cm soil layer by 18.96%,P20 treatment increased the root length in the 20-30 cm soil layer by 32.39%,P30 treatment increased the root length in the 30-45 cm soil layer by 28.73%.Compared with the P-all treatment,P10,P20 and P30 increased the root dry matter by 26.62%,30.74%,and 24.65%,respectively.The ANOVA results showed that the root dry matter in 0-10 cm and 10-20 cm soil layers were significantly higher in P10 treatment than in other phosphorus treatments,and the differences between other treatments were also significant.Under the conditions of this experiment,root sampling is limited to the buckwheat seedling stage,P10 had the best effect of phosphorus fertilization under water stress conditions.In the blooming period,with the increase in the degree of water stress,buckwheat root SOD,POD activity showed a trend of increasing and then decreasing,compared with W1 treatment,the root SOD activity per soil layer of W2 treatment increased by 33.71%,42.62%,46.77% and 41.32%,respectively;root POD activity of W2 treatment increased by an average of 43.73%,41.55%,39.42% and 42.03% respectively.The MDA content of the root system showed an increasing trend under the gradually increasing water stress.From the different depths of phosphorus application,regardless of soil moisture conditions,phosphorus fertilizer will improve the phosphorus layer of buckwheat root SOD,POD activity,reduce MDA content,and deep phosphorus application will be beneficial to this layer as well as the lower layer of the root antioxidant enzyme activity,reducing MDA content,which is conducive to alleviate the aging process of the lower layer of the root system.Eventually,the yield at maturity was improved.During the maturity period,with the increase in water stress,the yield and its components of buckwheat were significantly decreased,and the lowest value of each indicator was reached under the W3 treatment.Compared with the W1 treatment,the number of main stem branches,number of grains per plant,thousand grain weight and yield of W3 treatment decreased by an average of 23.77%,35.30%,9.66% and 14.13%,respectively.The highest values of all indicators were achieved under P20 treatment regardless of the moisture conditions.ii)The field experiment:From seedling to anthesis,regardless of the depth of phosphorus application conditions,buckwheat chlorophyll content,plant height and above-ground dry mass showed an increasing trend.In the seedling period,in the P10 treatment of buckwheat plants reached the best value of various indicators;in the anthesis period,in the P20 treatment of buckwheat plants reached the best value of various indicators.The main stem branching number,the number of grains per plant,thousand grain weight and yield of buckwheat at maturity were the best under the P20 treatment,and each treatment has formed a significant difference between P20>P-all>P10>P30.In summary,whether in the soil column experiment or in field experiment,appropriate deep application of phosphorus fertilizer will promote the growth and yield of buckwheat to varying degrees,under the conditions of this experiment,the phosphorus fertilizer concentrated in the 20-cm layer of the best results.Regardless of the soil moisture conditions,the deep application of phosphorus fertilizer to mitigate the damage caused by water stress,and thus promote the growth of buckwheat... |
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