Research Of Fertilization On Soil Fertility And Physiological Status And Yield Of Potato

Fertilization is one of the crucial measures to improve the yield and quality of crops.Still,excessive fertilization will decrease the gain,damage the soil structure and even pollute the environment.We aim to provide a scientific basis for rational fertilization of potatoes and soil fertility improvement.The long-term positioning fertilization experiment can usually systematically investigate fertilization effects on soil fertility.This research is based on the long-term fertilization experiment of potatoes established in Wuchuan County,Hohhot City,in 2010.Changes in soil physical and chemical properties,soil microbial community structure,potato plant growth physiology,and yield were studied after 7 to 10years of continuous fertilization.There are seven fertilization treatments:manure plus nitrogenous,phosphatic,and potassic fertilizer（MNPK）;manure（M）;nitrogenous,phosphatic,and potassic fertilizer（NPK）;nitrogenous and phosphatic fertilizer（NP）;nitrogenous and potassic fertilizer（NK）;phosphatic and potassic fertilizer（PK）;non-fertilization（CK）.The main findings are as follows:（1）Soil aggregate structure changed considerably under different fertilization treatments.In terms of soil water-stable aggregates,the contents of large aggregates with particle size greater than 250μm reached 85.5%in the treatment of M,which was significantly increased by 25.6%and 27.7%compared with NPK and PK,respectively.The contents of clay with the particle size of 20μm～53μm and microaggregates with the particle size of 53μm～106μm in NPK treatment were 12.54%and 6.56%,respectively,which were significantly higher than those in M,NP,NK and PK treatments.During the potato growth period,the soil volumetric water content variation could be described as a"（?）"type curve with the increment of soil depth.The soil water content was the highest in the 30～40 cm soil layer,and the variation range was 25%to 33%;NPK,M and MNPK in this layer were relatively high,and the water content of M and MNPK were very close.The soil water content of the soil layer below 40 cm varied considerably among all seven treatments.Furthermore,MNPK had the highest water content,with a varied range of 20%to 30%;The soil water content of NPK,PK,and CK decreased significantly,with a range of 3%to 30%.Long-term application of manure significantly reduced the soil bulk density of the cultivated layer.The soil bulk density in 0～20 cm layer of M and MNPK were 1.12 g·cm^-3 and 1.18g·cm^-3,respectively,which were significantly lower than NPK,PK,and CK by 10.4%,10.4%,9.7%and 5.6%,5.6%,4.8%,respectively.The soil bulk density of M treatment was the smallest in the 20～40 cm and 40～60 cm soil layers,which were 1.30 g·cm^-3 and 1.36g·cm^-3,respectively,but there was no significant difference with each treatment.The application of manure can significantly increase the porosity of the 0～40 cm soil layer.In the 0～20 cm layer,the porosity of the M treatment was 56.27%,which was significantly higher than that of the NPK,PK,and CK treatments,which were 4.2%,3.4%and 4.2%higher,respectively.The porosity of M in the 20～40 cm layer was 50.85%,which was significantly higher than that of NK and CK treatments,increasing by 3.6%and 3.1%,respectively.Long-term application of phosphatic and potassic fertilizers will increase the bulk density of 0～20 cm soil.（2）Both NPK and MNPK significantly reduced soil p H,and the soil p H of MNPK was7.9～8.0,and the p H value was reduced the most,which decreased by 0.2～0.3 compared to CK.Nitrogenous fertilizer is the main factor in lowering soil p H.A single long-term application of manure had no significant change in soil p H.Different fertilizers have little effect on the content of available nitrogen,and the range of available nitrogen in the nitrogenous fertilizer treatments and the manure treatments were the same.MNPK significantly increased the soil available phosphorus content.The available phosphorus content of MNPK in the 0～20 cm and 20～40 cm soil layers was significantly higher than that of NPK,with an average increase of 140.1%and 136.6%in each of the two years.The soil available potassium content increased significantly after applying potassic fertilizer treatments,and the available potassium content of NK increased the most.In contrast,the available potassium content of M,NP and CK were much lower than other fertilization treatments.We evaluated the soil quality based on the contents of available nitrogen,available phosphorus,available potassium and p H;MNPK significantly improved soil fertility quality,while the partial application of chemical fertilizer significantly reduced the soil fertility quality during potato tuber expansion,among which the lack of K fertilizer had the greatest effect.There was a significant positive correlation between soil fertility quality and tuber yield in 0～40 cm soil layer.The significance of the positive correlation between soil quality and tuber yield in 0～20 cm soil layer was higher than that in 20～40 cm soil layer.The contribution of soil fertility status to tuber yield in more than 40 cm soil layer was significantly reduced.（3）Different fertilization treatments significantly affected the development of soil bacterial and fungal communities in the cultivated layer.Theα-diversity analysis results showed that long-term application of manure significantly improved the dominance of the soil bacterial community and reduced the evenness and diversity of the community.The diversity of soil bacteria in each chemical fertilizer treatment was similar to that of CK.The diversity of the fungal community of M was significantly higher than that of MNPK and NK.Other chemical fertilizer treatments reduced the diversity of the soil fungal community to varying degrees.The relative abundances of Pseudarthrobacter treated with M,PK,and CK were higher than the other treatments.The abundance of Blastococcus and Nocardioides of M,MNPK,NPK,and CK were significantly higher than that of NP,NK,and PK.The abundance of Basidiomycota in M treatment was significantly higher than that of other treatments.The abundance of Chytridiomycota in NPK was significantly higher than that of the other treatments.（4）Long-term application of manure can significantly increase the plant height and stem thickness of potatoes,increasing the plant height by more than 10 cm and the stem thickness by about 4 mm compared with the potato treated with chemical fertilizers.Long-term application of manure significantly increased potatoes’leaf area index（LAI）.In 2016and 2018,the maximum LAI of MNPK and M treatments were 6.06,6.35 and 4.65,4.20,respectively,which increased by 50.0%～183.5%and 46.3%～203.9%compared with NPK,NP,NK,PK,and CK,respectively.In addition to manure application,nitrogenous fertilizer also has an essential effect on increasing plant height,stem thickness and LAI.The positive correlation between plant height,stem diameter,LAI,total photosynthetic potential and tuber yield was extremely significant.（5）The application of nitrogenous fertilizer significantly increased the SPAD value of potato leaves.The SPAD value results of NPK,NP,and NK,were significantly higher than that of M at the early stage of potato growth,and the SPAD value results of MNPK and NP were higher than the other treatments after 40 days of emergence.Under different fertilization treatments,the changes of potato leaf photosynthetic characteristics showed a single-peak curve law.The net photosynthetic rate of CK and PK was significantly lower than the other treatments,indicating that applying nitrogenous fertilizer can substantially promote the net photosynthetic rate of potato leaves.The stomatal conductance of NP,NK,and PK,was significantly lower than other treatments in the late growth period,indicating that partial application of chemical fertilizers reduced the stomatal conductance of potato leaves in the late growth period.The single application of manure significantly reduced the intercellular CO₂ concentration of potato leaves in the early growth period.All fertilization treatments did not significantly affect the transpiration rate of potato leaves.The net photosynthetic rate,SPAD and radiation use efficiency of potato leaves were positively correlated with tuber yield（p<0.01）.In contrast,stomatal conductance and transpiration rate were positively correlated with tuber yield（p<0.05）.（6）Long-term application of manure significantly increased the rate of potato dry matter accumulation.The single application of manure can make the potato enter the rapid dry matter accumulation period earlier,which was 4 to 11 days earlier than the other treatments except for PK,to increase the potato’s maximum dry matter accumulation.The dry matter quality of the main organs of MNPK and M were significantly higher than other treatments.Nitrogenous and potassic fertilizers also improved the dry matter quality of tubers.With the increase of fertilization years,the time gap between PK,CK,M and MNPK,NP,NK,NPK in potato reaching dry weight balance period was gradually increasing;PK,CK,M treatment spent 34～46 days,NPK,NK,NP,MNPK treatment needed 47～60 days to reach that period.The 4-year average potato yields of MNPK,M,NPK,NP,NK,PK,and CK from 2016 to 2019 were 27407 kg·hm^-2,28532 kg·hm^-2,21325 kg·hm^-2,16702 kg·hm^-2,and 16406 kg·hm^-2,15763 kg·hm^-2,13979 kg·hm^-2,the application of manure significantly increased potato yield.In addition,the application of manure significantly increased the rate of commercial potatoes and the number of tubers per plant.The number of tubers per plant of PK was significantly higher than that of the other chemical fertilizer treatments.M and MNPK treatments can significantly improve the stability and sustainability of potato yield.The application of manure can consider the formation of potato yield and soil fertility.The contribution rate of M and MNPK treatments to potato yield was significantly higher than that of other chemical fertilizer treatments.In contrast,the contribution rate of partial chemical fertilizer to potato yield was relatively low.The yield trend of potato in M and MNPK treatments was significantly higher than that in all chemical fertilizer treatments.The yield trend of potato in partial chemical fertilizer treatments was similar to that in no fertilizer treatment.