Effects Of Phosphorus Level On Yield And Main Nutritional Quality Of Foxtail Millet

Foxtail millet has the characteristics of barren tolerance,strong stress resistance and wide adaptability,and it is an important crop of both grain and grass in northern China.In the actual agricultural production process,unreasonable fertilization ratio and fertilization method not only caused the decline of fertilizer utilization rate,but also caused the increasing environmental pollution,which seriously affects the quality and yield of foxtail millet.Fertilizer plays an important role in the process of agricultural production in China as a decisive factor of grain yield increase.However,in recent years,the fertilizer consumption in China continually grow at a high speed,but the grain output has always increased slowly.Especially with the national advocacy of "reduce the use of chemical fertilizer",it becomes particularly important to improve crop fertilizer utilization,reduce input and improve output.Phosphorus is an essential macroelement for the growth and development of plants.Two thirds of the soil in China is short of phosphorus,and the phosphate rock resource is a non-renewable resource.Therefore,to select low phosphorus tolerant crops and to improve the phosphorus utilization rate of crops are becoming a “hotpoint” in current agricultural research.During this study,150 foxtail millet core germplasm resources with different sources and wide genetic variation were used as research materials.Combined with the analysis methods of indoor pot and field experiments,the characteristics of low phosphorus tolerance of different germplasm resources were identified.Single-factor,double-factor and multi-factor experiments were used to explore the utilization characteristics of phosphorus in foxtail millet,which further provided a theoretical basis for the popularization of foxtail millet variety promotion and high quality and high yield.The main results are as follows:（1）We screened the low phosphorus tolerance characteristics of foxtail millet germplasm resources at seedling stage and identified the extreme materials by indoor potted plants.150 foxtail millet germplasm resources were comprehensively evaluated by principal component analysis and membership function analysis.According to the comprehensive evaluation index D value,the materials were clustered and divided into five grades,among which,Grade I was tolerant to phosphurus,which contained 36 foxtail millet varieties,and Grade V was sensitive to phosphurus,20 varieties were in this group.（2）We analyzed the physiological responses of P sensitive and P tolerant materials at different P levels.We found that the activities of SOD,POD and CAT in foxtail millet were affected by different P levels,and there is a genotype effects;by measuring anthocyanin content,it was found that low P promoted the accumulation of anthocyanin content in foxtail millet,and under four P levels,the anthocyanin content of different foxtail millet varieties showed P0>P₄₅>P₉₀>P₁₈₀.In addition,on the same phosphorus level,the anthocyanin content of sensitive varieties was higher than that of tolerant varieties.Furthermore,the grain phosphorus content and phosphorus utilization efficiency of 4 foxtail millet varieties were measured under different treatments.When the amount of phosphorus application was 90 kg·hm^-2,the grain phosphorus content and phosphorus utilization efficiency of all foxtail millet varieties reached to the peak,and there were differences in grain phosphorus content and phosphorus utilization efficiency among different varieties.（3）We tested different combinations of N,P and K on the selected extreme materials in the field,and determined the agronomic characters and yield of foxtail millet under different treatments,in order to explore the effect of P on foxtail millet yield under the synergistic effect of N and K.The results showed that the effects of different phosphorus levels on the yield and its components of foxtail millet were different in the threshold of phosphorus induction of different varieties,and the response of phosphorus sensitive materials to phosphorus level was higher than that of phosphorus tolerant varieties.Reasonable ratio of N,P and K could significantly improve the agronomic traits of foxtail millet.There were significant differences in stem diameter and leaf area between different N,P and K treatments and the control（P < 0.05）,and T₆(N₁₆₀P₉₀K₁₅₀)treatment was the best.On the basis of nitrogen fertilizer,reasonable application of phosphorus and potassium fertilizer can significantly improve the agronomic traits of foxtail millet,and contribute to the growth and development of foxtail millet.Different fertilization combinations have certain effects on foxtail millet yield.Under T₆(N₁₆₀P₉₀K₁₅₀)treatment,the ear length（22.76cm）,ear diameter（3.15 cm）,single ear weight（42.08 g）,single ear grain weight（32.25 g）and yield(7351.12 kg·hm^-2)of foxtail millet reached to the maximum,and the difference between T₆(N₁₆₀P₉₀K₁₅₀)and control have obvious difference.（4）By determining the main nutritional quality of foxtail millet under different nitrogen,phosphorus and potassium treatments,we found that the grain protein content under different fertilization treatments was significantly different from that of the control（P < 0.05）.With the increasing of nitrogen application rate,grain protein content was gradually increased;with the increasing of phosphorus application rate,the fat content showed a trend of first increase and then decrease.On the four levels of phosphorus fertilizer,fat contents is expressed as P₉₀>P₁₈₀>P₄₅>P0;With the increasing of nitrogen application rate,the amylose content gradually decreased,under the four levels of phosphorus fertilizer,the amylose content had no significant difference.The amylose content was the best when the amount of potassium fertilizer was 150 kg·hm^-2.In conclude,T₆(N₁₆₀P₉₀K₁₅₀)treatment was the best after comprehensive comparison,which indicated that reasonable application of P and K fertilizer on the basis of nitrogen fertilizer could significantly improve the nutritional quality of foxtail millet.