| Micronutrients are indispensable nutrient elements for the growth and development of crops.Soil is the main source for the absorption and utilization of micronutrients by crops.Fertilization and crop growth and development are the main reasons affecting the change of micronutrients content in soil.Based on long-term fertilization experiments,this paper studied the effects of long-term application of nitrogen and phosphorus fertilizers,organic fertilizers,and straw returning on the spatial and temporal distribution of available micronutrients in soil,providing theoretical guidance for rational fertilization.The long-term fertilization test was set up in Shouyang County,Shanxi Province in 1992,which was designed as follows:Test 1,nine treatments:non-fertilization:N0P0M0;single nitrogen or phosphate fertilizer:N1P1M0,N2P2M0,N3P3M0,N4P4M0;organic and inorganic fertilizer combined:N2P1M1,N3P2M3,N4P2M2;single application of high amount of organic fertilizer:N0P0M6.Test 2,four treatments:straw not returned(CK);straw mulching(SM),straw crushing(SC),cattle manure(CM).The main research conclusions are as follows:(1)Interannual variation of micronutrients in cultivated soil(0?20 cm)under different fertilization treatmentsThe effective Fe content reduced from advanced to medium level when no fertilization or single application of nitrogen or phosphorus during the experiment for 15 to 20 years.In treatment N2P1M1,the effective Fe content reduced from advanced to intermediate level after 25 years.With the increase in the amount of organic fertilizer applied,the change of effective Fe content in N4P2M2 was small,which was still at advanced level.Effective Fe content were at advanced level and continued to rise in treatments N3P2M3 and N0P0M6.After 20 years of experiment,effective Mn content reduced from a medium level to a lacking levelin treatments:no fertilization,single application of nitrogen or phosphorus fertilizer,and N2P1M1..With the increase of the amount of organic fertilizer,the effective Mn content decreased,and in treatments N4P2M2 and N3P2M3,they were still decreasing year by year,which were still above the middle level.The effective Mn content in N0P0M6 treatment had an upward trend and was at an advanced level.Under treatments:no fertilization,single application of nitrogen or phosphorus fertilizers,low-medium organic fertilizer,the effective Cu contents were slowly decreasing,but overall remained at a high level.The effective Cu content of N3P2M3 and N0P0M6 treatments increased,from high levels to extremely advanced level.Under treatments:no fertilization,single application of nitrogen and phosphorus fertilizers,the effective Zn contents remained basically stable,but were in a lacking level.With the increase of the amount of organic fertilizer applied,the contents of effective Zn increased significantly,rapidly rising from low level to high and extremely high level.(2)Distribution characteristics of micronutrients in soil profile(0?100 cm)under different fertilization treatmentsThe effects of long-term different fertilization treatments on the distribution characteristics of available Fe,Mn,Cu,and B in the 0?100 cm soil layer profile had a certain similarity,that was,they made a greater impact on surface soils and less impact on deeper soils.In soil,the effective states of Fe,Mn,Cu,and B were greatly affected by the soil layers of 0-60 cm,0-40 cm,0-60 cm,and 0-20 cm,respecvtivly.Compared with the non-fertilization treatment,the single application of nitrogen and phosphorus fertilizers had less influence on it,and the difference between treatments was small.The application of organic fertilizers greatly increased the contents of available micronutrients in the affected layer,and with the increase in the amount of organic fertilizer,the increase of the content of micronutrients gradually increased.Long-term different fertilization had a greater effect on the effective Zn content in 0?20 cm soil,and a smaller effect on deep soil in 20?100 cm.Compared with the non-fertilization treatment,the effective Zn content in the combined application of nitrogen and phosphorus fertilizers had a tendency to decrease,and the difference between them was small.The effective Zn content in the soil treated with combined application of organic and inorganic fertilizers and single application of high amount of organic fertilizers had a larger increase.Long-term different fertilization treatments had a greater effect on the effective Mo content in 0?60 cm soil and a smaller effect in 60?100 cm soil.Compared with the non-fertilization treatment,the effective Mo content in the soil had a tendency to reduce in different fertilization treatments,and the decrease range in the combination of organic and inorganic fertilizers and single application of high amounts of organic fertilizers was smaller.(3)Interannual variation of micronutrients in cultivated soil(0?20 cm)treated with different straws returned to the fieldThe effective Fe content in topsoil of CK,SM,and SC decreased from high to medium level in 2011;the effective Fe content of CM treatment was basically stable,slightly increased,and at a high level.The effective Mn content in topsoil of CK,SM,and SC decreased from a moderate level to a lacking level in 2011.The effective Mn content of CM treatment in the plow soil also showed a downward trend,but remained at a medium level.The effective Cu content in the cultivated soil under different straw returning treatments showed a downward trend,but the CM treatment had the smallest decreasing range and remained at a high level.The effective Zn content in the cultivated layer soil treated with different straws returned to the field had a certain upward trend.After 2011,the effective Zn content in the cultivated layer had reached a relatively stable state,but the effective Zn content in the cultivated layer soil treated by CK,SM,and SC was still at a lacking level.The CM treatment increased from a lacking level at the beginning of the test to a medium level and then to a high level.(4)Distribution characteristics of micronutrients in soil profiles(0?100 cm)under different straw returning treatmentsThe effects of different straw return treatments on the distribution characteristics of available Fe,Cu,and Zn in the 0?100 cm soil layer profile were similar,and they had a greater impact on surface soils and less on deep soils.Compared with CK,the effective micronutrients content of the affected soil layer increased slightly in SM and SC treatments,and the difference between treatments was not significant.can the effective micronutrients content significantly increased in the 0?100 cm section in treatment CM.The effects of different straw return treatments on the effective Cu content in the 0?60 cm soil layer were obvious,which decreased in SM and SC,increased significantly in CM,ompared with CK.The effects of different straw returning treatments on the effective B content in the 0?60 cm soil layer were more obvious.Compared with CK,B increased in SM,SC,and CM,and increased most significantly in CM.The effects of different straw returning treatments on the effective Mo content in the 0?40 cm soil layer were more obvious.Compared with CK,the effective Mo content reduced,among which the reduction in SM was smaller and in SC and CM was larger.Fertilization recommendations are as follows:In the process of agricultural production,the simple application of nitrogen and phosphorus fertilizers and straw mulch and direct return to the field can not meet the needs of crops for trace elements.As the main source of trace elements in the soil,organic fertilizer needs to increase the application amount of organic fertilizer and the input of external micro-fertilizer to maintain the dynamic balance of trace elements during crop growth and development.It is recommended to apply appropriate amount of micro-fertilizer to supplement the deficiency of effective Mn,Zn,B and other trace elements in the areas of single application of nitrogen and phosphorus fertilizers and straw mulching and direct return to the field.The content of available Mo in the area selected in this experiment is at a relatively high level,and no supplement is needed at this stage.The application of organic fertilizer can significantly increase the content of trace elements in the soil,and the area where only organic fertilizer(cow dung)is applied should also be supplemented with manganese fertilizer and boron fertilizer in an appropriate amount.The experiment shows that the balance of medium and high amount of organic fertilizer and nitrogen and phosphorus fertilizer combined with soil micronutrient nutrition is better. |
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