| Aiming at the problems of draught and soil and water loss in the slopping farmland in semi-arid region of western Heilongjiang province,the measures of minimum tillage with partial deep loosing(SGS),no-tillage with straw cover(MG),furrow damming(LQ),the combination of film mulching and furrow damming(FQ),the combination of deep loosing and furrow damming(SQ),the combination of film mulching and deep loosing and furrow damming(FSQ) were selected.Through the experiments of rainfall-runoff plots in Gannan County in 2006,2007 and 2008,the characteristics of rainfall-runoff,infiltration,soil water redistribution,soil water storage,water balance,soil erosion and their simulation were studied. The results are as follows.The tillage measures had the effects of evaporation control,runoff reducing and infiltration enhancing respectively.The organically combination of some single technologies had the good effects for water saving and soil and water conservation.The effects of runoff control differed from the tillage measures.For annual runoff, compared with conventional tillage(CK),the treatment of SQ with the best result of 95.1% runoff reducing ranked the first place,followings were the treatments of FSQ,LQ,FQ,SGS, MG with the runoff reducing rate of 91.3%,76.3%,71.4,19%,18.1%respectively.The experiments under the natural rainfall condition showed that,before the construction of furrow dams,the treatment of LQ is almost same with CK,and after the dams construction,LQ had a good result for runoff control,all the treatments with LQ were all no runoff normally,the runoff happened only when some of the dams were damaged.Deep loosing had a good effect of infiltration enhancing;the treatments with it had a minimum runoff.SQ had no runoff, which indicated that there is an obvious advantage for the combination of deep loosing and furrow damming technologies.When the rain was heavy,film mulching had the effect of runoff increasing,but it was not when the rain was not heavy,this is more suitable for the region according to the nature condition.The experiments under artificial rainfall condition showed that,the effects of runoff control differed from rainfall intensities.When the rainfall intensity was 40ram/h,LQ and FQ had no runoff yield,when the rainfall intensities up to 60mm/h and 80mm/h,the runoff yields were about 25%of the CK.The runoff effect of MG was higher than CK and lower than the others.Combine these with those of the natural rainfall condition,we can come to the conclusion that LQ and FQ must be combined with deep loosing technology which can intensify the infiltration when the rainfall intensity is higher than 40mm/h,otherwise some of the dams is easy to damage due to the water pressure formed by rain water accumulation.With the initial soil water content decrease,the times of the runoff start and the peak present were delayed,and the runoff yield was decreased.The influences of tillage measures on infiltration were obviously.The order of the rate of infiltration rate decreasing from fast to low was:LD, FQ(before the dams construction),CK,MG.,SGS,FQ(before the dams construction),LQ.The order of stable state infiltration rate from big to small was FQ,LQ,SGS,MG,CK,FQ*,LD. There was a good relation between the decreasing rate of infiltration rate and rainfall intensity for all of the treatments.The more rainfall intensity,the faster decreasing rate and the earlier stable state infiltration rate present.Generally,stable state infiltration rates were decrease with the rainfall intensities increase.There were index function relations between stable state infiltration rates and rainfall intensities for FQ and LQ,and power function relations for others. There were some influences of initial soil water contents on infiltration,the higher soil water content,the faster infiltration rate decreasing,the lower stable state infiltration rate.The relation between initial soil water content and stable state infiltration rate could be described by index function.There some influences of rainfall amount on soil profile water content variation,the variation of the depth for rainfall supply was lower.The obvious variation of soil water contents was in 0-60cm soil layer for LD,0-70cm for CK,and about 0-80cm for other treatments,there were no changes for deeper layers.The consumption of soil profile water contents were affected by tillage measures,in which the lowest one was FSQ,followed by FQ, SQ,MG,LQ,SGS,CK and LD respectively.The variations of soil water storage in 0-100cm layer in observation period were mainly affected by the processes of rainfall and evapotranspiration.Soil water storage amount in 0-100cm layer for different tillage treatments were all with the circles of up and down,the trend of them was almost same with annual rainfall process,and soil water storage amount was generally going up in observation period,soil water contents variation mainly happened in the layer of 0-60cm,and change sharply in 0-10cm layer,the layers equal to and deeper than 80cm no obvious change.The observation period could be divided into two periods,first is soil water stable period of May to the beginning of Jun,in the period the frozen soil melting and evaporation made the soil moisture increase and decrease respectively.The second period is soil water unstable period of the middle of Jun to August,in the period soil with circles of dry and wet.The results of water balance analysis for 0-100cm layer in observation period showed that, the soil water storage for LD and CK were in the state of negative compensation. Evapotranspiration amount was lowest in LD,followed was CK.SQ,FSQ,LQ were all most same and in the highest level,in which the FSQ was the lowest.FQ,MG and SGS were in the middle. There was a good consistency between seasonal distributions of soil erosion load for all of the treatments and rainfall.There were big influences of tillage measures on annually soil erosion load,the degrees of the influences differed from the measures.The order of soil erosion load from big to small was LD,CK,SGS,LQ,MG,FQ,SQ and FSQ.The degrees of soil erosion were improved in some extent after taking the tillage measures,in which the soil erosion loads of FSQ,SQ and FQ were much lower than the allowed value.Under the natural rainfall condition,there were a good consistence and corresponding between sediment and rainfall processes,and rainfall intensity had an obvious influence on sediment process.Artificial rainfall experiment showed that,soil erosion load were increased with rainfall increase,but the increasing rate of sediment yield was decreased when the rainfall intensity was increased up to some extent.Accumulated sediment generating processes in different tillage measures,different rainfall intensities and different initial soil water contents all could be described by power function.The combination of Kinematic Wave model and Green-Ampt model,Kostiakov model, Richards soil water movement equation,Support vector machine model can simulate surface rainfall-runoff processes,rainfall-infiltration processes,profile soil water dynamic variation and annual soil erosion load respectively in the region,all of them can be used in the semi-arid region of western Heilongjiang province.
|
PDF Full Text Request