| Low precipitation and high precipitation variability climatic characteristics in the Loess Plateau determines the water shortage natural environmental conditions and it is the main limiting factor for dryland crop production.In order to improve the spring maize production,breaking water limitation,the rain saving and water conservation techniques such as straw mulching,gravel cover and plastic film mulching are widely used.Surface cover influences the soil temperature and water,and then the rate of soil organic nitrogen mineralization was changed,and the yield and biomass of different organs in maize were also affected by different mulchings.This view is the basis on the hypothesis.Resin core technique method is the most commonly used in situ for soil nitrogen mineralization in field situ experiment.It has been widely used in forest and grassland nitrogen mineralization research.However,it is rare used to research the farmland nitrogen mineralization that surface coverd by plastic and straw or something.Based on the above two problems,this experiment relies on the long-term positioning test on Changwu Ecological Experimental Station,sets up three treatments,includeing control non-covering contrast treatment(BP),straw mulching(SM)and plastic film mulching(FM),adopts resin core technique method to provide a reasonable covering method and find out nitrogen mineralization under different treatments about farmland through organ biomass of each important growth stages and corn yield after harvest.The main findings are as follows:1、Straw mulching and plastic film mulching significantly affected the 0 ~ 25 cm soil temperature.The soil average temperature of SM decreased 0.4 ℃ and FM treatment increased 1.3 ℃ in 2015.In 2016,the soil average temperature of SM decreased 0.7 ℃ and FM also increased 0.6 ℃.At different growth stages,the effects of coverage on soil temperture are also differernt.The temperature of 0 ~ 25 cm soil layer was FM> BP> SM at different growth stages in both years,and the plastic film mulching significantly increased the soil temperature.Straw mulching and plastic film mulching also increased the 0 ~ 20 cm soil water content.In 2015,the SM increased the water content 9.8% and the FM was 14.3% compared with BP,and the same tend also appeared in 2016 that the number of growth are 5.7% and 17.2%.The effect of plastic film mulching at different stages was different about soil water content: the soil water content of film mulching in 2015 and 2016 was significantly higher than contrast at PT-V10,but there was no significant difference in the later fertility stage.2、The soil nitrogen in 0 ~ 20 cm layer was net immobilization under different surface coverage conditions.However,the net immobilization was mainly showed in per-period of whole growth.The net immobilizations of the plastic film mulching,straw mulching and noncovering were 68.0 mg kg-1,20.0 mg kg-1 and 17.9 mg kg-1,and the net mineralizations were 14.7 mg kg-1,1.2 mg kg-1 and 16.7 mg kg-1 in 2015;The net immobilizations of the plastic film mulching,straw mulching and non-covering were 56.7 mg kg-1,52.7 mg kg-1 and 53.7 mg kg-1,the net mineralizations were 13.7 mg kg-1,31.8 mg kg-1,26.3 mg kg-1 in 2016.The net immobilization and the net mineralization in 2015 is less than 2016.3、The results showed that the different treatments nitrate nitrogen content in resin was SM(11.2mg kg-1)> BP(11.1mg kg-1)> FM(3.8mg kg-1)at the whole growth period in 2015;The different treatments nitrate nitrogen content in resin was SM(10.5mg kg-1)>BP(9.4mg kg-1)>FM(2.0mg kg-1)at the whole growth period in 2016,it had the same trend in both years.The adsoption of nitrate nitrogen in the resin is highly consisitent with the rainfall intensity and rainfall.The net mineralization of straw mulching was significantly higher than contrast group,so the high mineralization also increased leaching risk of mineral nitrogen in 0 ~ 20 cm soil layer.The plastic film mulching significantly increased soil temperature and water of 0 ~ 20 cm soil layer,but the net mineralization and net mineralization rate did not increase significantly.4、The research shows that the straw mulching reduced the organs biomass at every important growth periods in two years but showed plastic film mulching showed an increasing trend.Comparing with the non-covering treatment,straw mulching redeced plant total biomass in each important growth stages such as V10,R1,R3 and R5,respectively 6.2%,13.2%,11.9% and 17.1% and the plastic film mulching increased by 47.8%,26.4%,20.6% and 19.2% in 2015.The straw mulching decreased plant total biomass in V10 and R1 by 6.7%、18.8% but increased biomass in R3 and R5 by 0.6% and 4.1% in 2016,and the plastic film mulching increased plant total biomass in each important growth stages such as V10,R1,R3 and R5,respectively 62.6%、23.4%、25.1% and 23.4%.5、Different surface coverage conditions affected maize production by changing the environment factors.Maize production fell partly by 18.8% and 36.1% in 2015 and 2016.Plastic mulching increased corn yield partly by 6.4% and 20.1% in two years.Although straw mulching increased soil moisture,the lower soil temperature effected seedling stage and the organ biomass in last stages,which affected the normal growth of maize during the whole growth period and reduced the maize yield.It is better to use plastic mulching in dry land considering the effect on nitrogen mineralization and maize yield. |
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