Effects Of Nitrogen Fertilizer Pursuit Periods On Yield And Nutrient Absorption Of Sweet Potato Intercropped In Different Symbiotic Periods

In order to explore the effects of nitrogen fertilizer pursuit periods on the yield and nutrient absorption of sweet potato in different symbiotic periods under maize/sweet potato intercropped mode,the best suitable nitrogen fertilizer pursuit period for the formation of sweet potato yield and compound yield was selected,and the optimum symbiotic period under maize/sweet potato intercropped mode was found.A intercropping split-plot experiment with two factors were used to design,and the materials of sweet potato cultivars were Yu shu 33,according to the different time of sweet potato planting,there were different maize/sweet potato symbiotic periods in intercropping,which was the main factor.In the case of nitrogen fertilizer(urea)90 kg/hm~2,phosphorus(P2O5)45 kg/hm~2,potassium(K2O5)180 kg/hm~2 fertilizer as the base fertilizer application rate of the same time,to pursuit nitrogen fertilizer(urea)60 kg/hm~2 at 10 d,20d and 30 d after planting sweet potato,which was a secondary factor.During the intercropping period of sweet potato/maize,the changes of soil environment,photosynthetic carbon assimilation ability of sweet potato functional leaves,the absorption and transformation of light energy were measured,the accumulation of photosynthetic products,the accumulation of plant nutrient and soil nutrient content were measured in sweet potato harvest period,and the results showed that:1 Effect of different treatments on photosynthetic characteristics of sweet potato functional leavesThe symbiotic period significantly or extremely significantly affected the net cropping photosynthetic rate(Pn),stomatal conductance(Gs),intercellular CO2 concentration(Ci),transpiration rate(Tr)of sweet potato functional leaves,but nitrogen fertilizer pursuit period has no significant effect on it.In the net cropping,the interaction of the two factors extremely significantly affected the(Pn)of sweet potato functional leaves.In intercropping,the interaction between the two factors significantly or extremely significantly affected the(Ci)of sweet potato functional leaves.Intercropping in 2018,the interaction between the two factors significantly affected the(Gs),(Tr)of sweet potato functional leaves.Prolonging the symbiotic period had a tendency to increase the Chlorophyll a(Chla),Chlorophyll b(Chlb),Chla+Chlb of sweet potato functional leaves,to reduce the Chla/b of sweet potato functional leaves.In intercropping,the Chla,Chlb,Chla+Chlb of sweet potato functional leaves was higher than that of net,Chla/b is the opposite.In intercropping,the delay of nitrogen fertilizer pursuit period had a tendency to reduce the Chla,Chlb,Chla+Chlb of sweet potato functional leaves,but that of net is the opposite,in addition,in net cropping and intercropping,the Chla/b of sweet potato functional leaves showed an increasing trend.In intercropping,the content of Chla in sweet potato changed relatively little,and the total chlorophyll content was mainly affected by Chlb,it varied with the change of Chlb content.In the net cropping,the content of Chlb in sweet potato changed relatively little,and the total chlorophyll content was mainly affected by Chla,it varied with the change of Chla content.2 Effect of different treatments on sweet potato yieldProlonging the symbiotic period significantly or extremely significantly increased the yield of sweet potato,compound yield,The highest yield was achieved in the 60-day symbiotic period,and the performance was consistent in the net cropping.Under different planting modes,the net cropping yield was higher than that of intercropping,and significant differences were found between some treatments.Nitrogen fertilizer pursuit period had no significant effect on sweet potato yield,Sweet potato had the highest yield in net cropping and interplanting after planting sweet potato 30 d treatment,and in the net cropping,the yield of sweet potato was basically unchanged under different nitrogen fertilizer pursuit periods.The highest yields of net cropping and intercropping of Xiema in 2017 were 2981.88 and 1649.29 kg/667m~2 respectively;In 2018,the test site of Hechuan was 2119.42 and 1438.48 kg/667m~2;In 2018,the test site of Xiema was 2220.00 and 1787.78 kg/667m~2.The highest compound yields of 2017 Xiema test site,2018 Hechuan test site,and 2018 Xiema test site,were 909.79,969.40 and 919.66 kg/667m~2 respectively,and in intercropping,the yield increase per mu was 112.62%,208.53% and 107.13% respectively;The highest compound yield was achieved in the 60-day symbiotic period.The performance was different under different nitrogen fertilizer pursuit periods.Compared with the highest compound yield and the yield increase per mu in three years,it was found that the early stage of planting sweet potato and the delay of nitrogen fertilizer pursuit period were beneficial to the increase of compound yield and he yield increase per mu.3 Effects of different treatments on nutrient accumulation of sweet potato plants and nutrient residues in soil during harvest periodThe prolongation of the symbiotic period extremely significantly increased the nitrogen content and potassium content of sweet potato plants in the harvest period,and reduced the nitrogen residue of soil,but that of net is different.the extension of growth period only extremely significantly increased the potassium content of sweet potato plants in the harvest period,and there was no significant difference in other nutrient content.There was no significant difference on nutrient accumulation of sweet potato plants and nutrient residues in soil during the different nitrogen fertilizer pursuit period.Prolonging the symbiotic period is beneficial to the absorption of soil nutrients in sweet potato plants and the reduction of soil nutrient residues.