Ecological Effect On Farmland With Different Rotational Tillage Patterns In Fallow Of South Ningxia Region

The southern mountainous region of Ningxia is located in the semi-arid of Loess Plateauin in northwest China, the long-term conventional tillage is the main soil tillage mode, strong invalid evaporation, serious soil and water erosion, lead to soil fertility obviously decreased and low level of agricultural productivity. The research in ecological effects of different tillage measures in dryland of south Ningxia to improve the system of dryland tillage techniques, soil physical structure and the productivity of rainfed areas, it has important theoretical and application worth. The study Carried out the trial of different combinations of subsoiling (ST), no-tillage (NT), conventional tillage (CT) in Northwest A&F University dryland experiment station in Guyuan Ningxia from2007to2010,research the impact of different rotation tillage on soil physical and chemical properties and crop growth. The main results are as follows:1After three years of winter fallow experiment, the soil bulk density of different tillage treatments decreased to CT, and the soil porosity improved. The soil bulk density of different tillage treatments in depth of0-20cm has significantly decreased. compared with CT. ST. NT/ST/ST, ST/NT/ST. NT and ST/NT/NT treatments were decreased by4.8%,4.7%,3.9%(P<0.05),1.5%and1.2%(P>0.05). in depth of20-40cm and40-60cm. the difference was not significant. The soil porosity in depth of0-20cm the difference of different tillage treatments were not significant, in depth of20-40and40-60cm,. compared with CT,NT treatment was the highest.it increased by3.7%and5.1%(P<0.05).2After years of different fallow periods rotational experiments show that the advantages of storage soil moisture of the different tillage treatment is obviously.in the average year (2009),from greening stage to maturity the soil moisture content in0-200cm layer under different tillage of summer fallow period is NT>ST>CT, while the winter fallow period in millet growth stage, the highest is NT/ST treatment, the second is ST: in a wet year (2010),in summer fallow periods rotational experiment of winter wheat, the highest of moisture content at different growth stages are NT/ST and ST. followed by ST/NT and NT treatment, in winter fallow period rotational experiment, in the different growth stages of Millet, the soil water content of ST/NT/NT and NT treatments was significantly higher than the other tillage treatments.3After three years of winter fallow experiment results show that the soil organic matter of NT/ST/ST is the highest in0-40cm depth, it higher than CT and increased by14.5%(P<0.05),the AN content of NT was higher than CT, and another of different rotational tillage were decreased, the AN content of ST was increased in0-20cm depth and decreased in20-40cm depth, the AP content of ST/NT/ST was the highest, compare with CT,the AP content of ST、NT、NT/ST/ST and ST/NT/NT were decreased, in0-20cm depth, the AK content of ST/NT/NT were increased by13.1%. Two years of summer fallow experiment results show that the organic matter content of NT and NT/ST were increased by10.9%(P<0.05) and4.1%(P>0.05), the AN content of NT/ST, NT and ST/NT were significantly higher than ST and CT (P<0.05); the AP content of ST/NT and NT/ST were higher than CT increased by31.7%(P<0.05) and7.4%(P>0.05), NT and ST were significantly lower than the CT (P<0.05):compared with CT, NT and rotational tillage treatments significantly improve the content of AK(P<0.05). The difference was not significant in20-40cm depth in all treatments between the AN content; the AP content of the ST/NT was significantly higher than CT. increased by16.2%(P<0.05) than CT; the ST/NT and ST of AK content were significantly lower than the CT.4After three years of winter fallow experiment results show that the years of NT treatment can promote the mechanical stability of aggregates in0-30cm depth, increasing the diameter of the aggregates.and promote the formation of water stable aggregates in0-40cm. The soil aggregates quantity(weight percentage) of continuous CT and ST is lower than other treatments, smaller diameter, higher destruction rate, the ST is obviously. NT was higher in macro-aggregate content (R0.25). mean weight diameter (MWD) and geometric mean diameter (GMD) than other treatments at10-30cm. MWD and GMD of water stable aggregates under NT was the highest and ST was the lowest at10-40cm. no-tillage more than two consecutive years could increase the aggregation and the stability of soil aggregates, while due to intense disturbance, subsoiling tillage and conventional tillage were increased the destruction rate of aggregate and decreased the stability of soil structure.5Compared with conventional tillage, the chlorophyll relative content at the flowering and filling period.under ST, NT/ST. ST/NT and NT were increased by32.2%,27.6%.13.5%and11.1%,respectively;the flag leaf daily average photosynthesis rate(Pn) of different tillage treatments were increased by1.63.1.19.0.96μmol·m-2·s-1and0.60μmol·m-2·s--(P<0.05); transpiration rate (Tr) of different tillage treatments were increased by1.22,0.86,0.70mmol·m-2·s-1and0.27mmol·m-2·s-1(P<0.05).The water use efficiency of flag leaf with ST and NT/ST were significantly higher than CT. At the two growth period, the values of Fv/Fm, Fv/Fo,φPSⅡ, qP and qN with four tillage patterns were significantly higher than that with conventional tillage, but the1-qP/qN values were significantly lower.6Years of experiment showed that different tillage treatments can increase crop yields, improve crop water use efficiency. Winter fallow experiment, after the millet harvest in2010, grain yield of NT/ST/ST、NT、ST、ST/NT/NT and ST/NT/ST higher than CT, they were increased by29.4%,25.9%,23.9%,20.3%(P<0.05) and3.5%(P>0.05);the regular of water use efficiency is NT/ST/ST>NT>ST>ST/NT/NT>ST/NT/ST>CT. Summer fallow experiment results show that both the yield and water use efficiency of winter wheat, the regular is NT/ST>ST>ST/NT>NT>CT, compared with CT, the yield of different tillage treatments were increased by42%,35%,30%and24%(P<0.05);and water use efficiency increased by51%,38%,20%and15%(P<0.05).