Effects Of Different Tillage On Physicochemical Properties Of Farmland Mollisoil And PSⅡ Function Of Maize Leaves

The mollisoil degeneration is threatening the food security of our country.In the long term,traditional tillage resulted in many adverse impacts,for instance,the increasing of microaggregate,decreasing of porosity in black soil,and weakening of drainability and water-retaining ability,which caused the soil and water erosion,fertility decline and soil hardness.Different tillage can exert distinct effects on soil physicochemical properties.Therefore,the effects of different tillage on soil properties were evaluated,which is a important solution to deal with mollisoil degeneration in farmland.In this experiment,mollisoil was performed at Dongguan town,Shuangcheng district,Harbin city of Heilongjiang province.The traditional tillage method of deep tillage（DN） was used as the control,the effects of no tillage（NN）,rotary tillage（RN） and subsoiling（SN） on soil physicochemical properties and PSⅡ function of maize leaves had been taken into consideration.Combining the effects of different tillage methods on the growth characteristics of maize,it can provide the theoretical basis and basic data support for exploring the most suitable tillage measure for the mollisoil in Northeast of china.The results were as follow:（1）Effects of different tillage on the physical properties of mollisoilThe effects of different tillage measures on the physical properties were significant.During sufficient rainfall months,compared with DN treatment,NN and RN treatment were more beneficial to water conservation in the tillage soil layer,while SN treatment was beneficial to water filtration.During less rainfall months,compared with DN treatment,SN treatment was beneficial to water conservation.The NN treatment could lower the soil temperature of superficial layer（10 cm）,and the temperature differences were not observed among other treatments.Compared with other treatments,the soil,after NN treatment,has comparatively less artificial disturbance,higher soil intensity and bulk density in 0-15 cm layer,in contrast,these characteristics were opposite.,Aggregate（>0.25mm）and the aggregate stability were higher in SN and NN treatments.（2）Effects of different tillage on the nutrients of mollisoilSignificant differences of soil nutrient were observed in different tillage and these effects were relevantly distinct in different period.The available phosphorus,available potassium and total phosphorus of soil were the lowest in DN treatment,while the variation tendency of total nitrogen,slowly available potassium and organic matter were unapparent.The p H value of soil was highest in DN treatment in all period,but p H were low and no significant differences were observed in SN,RN and NN treatments,owing to buffering power of these treatments werecomparatively strong.（3）Effect of different tillage on PSⅡ function of maize leavesThe V_J and V_I values of maize leaves in NN treatment were higher than other treatments,which indicated NN treatment inhibited the activity of PSⅡreaction center.Under NN treatment,the V_K and V_Lvalues of maize leaves were obviously higher than others,which indicated that the receptor side electron transfer of PSⅡ reaction center and the function of donor side Oxygen-Evolving Complex（OEC）of PSⅡ reaction center in maize leaves was decreased in NN treatment,likewise,the photochemical activity of PSⅡ reaction center in maize leaves was declined.PI_ABS,PI_total and ETo/RC were highest in SN treatment compared with others treatments,which indicated that SN measure could strengthen the activity of PSⅡ reaction center in maize leaves.The DIo/RC and TRo/RC of maize leaves in NN treatment were lower than other treatments,which indicated that the function of PSⅡ reaction center was declined.（4）Effect of different tillage on the growth characteristics of maize Different tillage treatments could exert distinct impacts on the growth characteristics of maize,compared with other treatments,the length,volume and superficial area of maize root were lower in NN treatment,in contrast,these indexes presented opposite tendency in SN treatment.When comparing with other treatments,in the seedling stage,the dry weight of both aboveground and underground were lower in NN treatment.These indexes,however,were higher in SN treatment.To sum up,in the short term,among all the tillage treatment,SN measure is beneficial to improve soil structure,strengthen the activity of PSⅡ reaction center in maize leaves,increase the readily available nutrient of soil and promote maize growth during seedling stage.Comparing with DN treatment,NN and RN treatments could improve the physicochemical properties comprehensively,but the soil hardness and bulk density were relatively high,which were not good for the root growth and the accumulation dry weight of maize during the seedling stage.Therefore,it is necessary to conduct long term and locate research about the impact of different tillage on the mollisoil.