Study On Effects Of Water And Fertilizers Of Alfalfa Under Subsurface Drip Irrigation And The Spatial Variability Of Soil Nutrient And Water Under Center Pivot Irrigation System In Ningxia

In this paper,for the problem of the effect of water and fertilizers yield under subsurface drip irrigation spatial and spatial variability of soil nutrient and water under center pivot irrigation system on alfalfa.By means of uniform design and geostatistics,the effect of water and fertilizer on alfalfa under the drip irrigation and the spatial variation of nutrient and water under center pivot irrigation system was studied systematically.The results provided the theoretical basis for the popularization of alfalfa water saving irrigation under the conditions of alfalfa with subsurface drip irrigation and center pivot irrigation system in arid region of Ningxia.The main research results were as follows;（1）The effect of four factors of water,phosphorus,phosphorus and potassium on the yield of alfalfa was studied by using uniform design experiment.Under different drip irrigation conditions,the effects of different irrigation and fertilization on the fresh and dry yield of alfalfa were significant（P<0.05）.The optimum combination scheme of alfalfa irrigation and fertilization was as follows:irrigation quota 165.67 m3 667m-2,pure nitrogen（N）4.51 kg-667m-2,pure phosphorus（P2O5）5.95 kg-667m-2,pure potassium（K2O）9.67 kg·667m-2.The treatment 1 had the greatest water production efficiency of fresh and dry of alfalfa,which was 7.14 and 1.90 kg-m^-3,respectively.The treatment 2 had the least water production efficiency of fresh and dry of alfalfa,which was 5.09 and 1.35 kg·m^-3,respectively.（2）The spatial variation rule of soil nutrient in center pivot irrigation system area was revealed by using traditional statistics and geostatistics methods.The correlation between different soil depth in center pivot irrigation system area was significant,and the PH₂0 and PH₄0 were significantly negatively correlated with total Salt₂0 and Salt₄0（P<0.01）.The alkali nitrogen AN₂0 was significantly positively associated with PH₂0 and PH₄0（P<0.05）;The AN₄0 was positively associated with PH₄0（P<0.05）;There was a significant positive correlation between AP₂0 and AP₄0（P<0.01）.Instant potassium AK₂0 was significantly associated with PH₂0 and AP₄0（P<0.05）.The 0-20 cm soil depth AK,AP,organic matter OM,AN and Salt had a spatial range of 267.86,96.1,86.21,81.23,and 75.59 m.0-20 cm soil depth AN,AP,OM’s C₀/C₀+C at 11.27%to 21.49%,all showed strong spatial correlation;PH,Salt,and AK’s C₀/C₀+C,were between 30.15%and 50.14%,showing a moderate correlation.The 20～40 cm soil depth Salt,OM’s C₀/C₀+C was 18.42%and 16.41%respectively,showing strong spatial correlation.The remaining indicators showed a moderate correlation between 25.57%and 39.80%.（3）The spatial and temporal variation of soil moisture in center pivot irrigation system area was revealed by using traditional statistics and geostatistics methods.Correlation coefficient of soil moisture content in different soil depth decreases with the increase of distance,in addition to 20 cm and 100 cm soil depth in correlation between moisture content reached significant level（P<0.05）,the rest of the relationship between soil moisture content of different soil depth is reached significant level（P<0.01）.Soil moisture content range between 43.2～142.2 m,with the increase of the depth had a tendency to increase,20 cm,moisture content of 40 cm,60 cm,80 cm,100 cm soil depths range were 47.1,43.2,69.3,103.2,142.2 m.The C₀/C₀+C of soil moisture contente[10.10%,15.04%]was less than 25%and had strong spatial correlation.The soil water space was migrated with changes in irrigation,rainfall and time.（4）Based on the traditional statistics and geostatistics methods,the correlation of soil nutrient,water and alfalfa production in the control area of center pivot irrigation system and the spatial variation rule of alfalfa production were revealed.Alfalfa production had a significant relationship with soil nutrient and moisture content.The C₀/C₀+C of the first,third and full-fertility crop alfalfa production were 18.16%,11.63%and 15.66 less than 25%,with strong spatial correlation.The second crop alfalfa yield C₀/C₀+C was 47.44%E[25%,75%],and there was moderate spatial correlation.Under center pivot irrigation system,the first crop of alfalfa had the biggest water production efficiency,which was 7.41 kg-m^-3,the second crop of alfalfa had the least water production efficiency,which was 5.58 kg-m^-3,and full-fertility crop alfalfa water production efficiency was 6.46 kg·m^-3.