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Gansu Agricultural University (2008)

Integrated Evaluation On Soil Quality Under Different Tillage Systems In Semi-arid Area Of The Loess Plateau

Luo Zhu Zhu

Titre : Integrated Evaluation On Soil Quality Under Different Tillage Systems In Semi-arid Area Of The Loess Plateau

Auteur : Luo Zhu Zhu

Grade : Doctoral Dissertation 2008

Université : Gansu Agricultural University

Résumé partiel
In 2001,Gansu Agricultural University started a long-term conservation tillage project,funded by Australian Centre for International Agricultural Research,at Lijiabu Village,Dingxi,Gansu Province.The overall aim of the project was to study the effects of conservation tillage on crop productivity and soil quality,the adaptation of conservation tillage in the Loess Plateau where soil is prone to severe erosion,and its underlying mechanisms.The PhD project was part of this long-term project.There were six treatments with two tillage systems and three ground covers,namely conventional tillage (T),no-till without stubble retention(NT),conventional tillage with stubble incorporated (TS),no-till with stubble retention(NTS),conventional tillage with plastic film mulch(TP) and no-till with plastic film mulch(NTP).The experiment was fully-phased with two rotation sequences.Phase 1 started with field pea followed by spring wheat(P→W) whereas phase 2 started with spring wheat followed by field pea(W→P).The objectives of this thesis are:1) to quantitatively analyze effects of soil chemical,physical and biological properties on soil quality and productivity under different tillage systems and the driving factors for the changes of soil quality under tillage in a long-term,2) to select the best soil quality assessment indicators,and 3) to establish soil quality assessment models that are suitable for the erodible environment of semi-arid region on the Loess Plateau.The key results from the study are summarized as follows:1) The study selected 8 most sensitive indicators out of 29 assessment indictors that are used to evaluate soil physical quality,soil fertility,soil health and land productivity in the semi-arid region in the Loess Plateau.These 8 indicators were water stable aggregates,organic matter,total nitrogen,available nitrogen,invertase activities,grain yield,net income,ratio of output and input.The integrated assessment models established using the addition and multiplication method and weighted integrated method for soil quality assessed under different tillage systems,and the results from two assessment systems were similar and highly correlated.This showed that these 8 indicators could provide the best fit for the actual situation in the western Loess Plateau. 2) Soil quality can be improved by NTS.The order of integrated soil quality index(ISQI) from high to low was NTS,TS,NTP,NT,T and TP in P→W rotation,and NTS,TS, NT,NTP,T and TP in W→P rotation.No-tillage and stubble retention,in general,can improve soil structure,reduce soil and water erosion and soil nutrient loss,and hence increase crop productivity.This will,in turn,increase organic material returned back to soil,ensuring the high reproduction and activity of soil organisms.Accordingly,soil biological activity is conducive to improvement of soil structure and soil fertilizer.As a result,the healthy farmland ecosystem is built,thus inducing improved soil quality. Moreover,soil physical quality,fertilizer quality,soil health and integrated soil quality in W→P rotation were higher than that in P→W rotation.On the contrary,Soil productivity in W→P rotation was lower than that in P→W rotation.4) Soil physical quality can be improved by NTS.Soil water,soil structure and water infiltration rather than soil temperature were the dominant indictors for soil physical quality.The order of soil physical quality index(SPQI) from high to low was NTS,NTP, NT,TS,T and TP in P→W rotations,while the order of SPQI was NTS,NTP,TS,NT, TP and T in W→P rotation.This indicated that NTS have the strongest effect on soil physical quality.There is no big difference among different treatments’ bulk density and total porosity,but Non-capillary porosity and aggregates under NTS was greatly improved,enhancing soil infiltration and reducing runoff and sediment.Surface soil water content under no-till with stubble retention was greatly improved up to 56% compare to conventional tillage,although there is no big difference among different treatments’ water storage at 0-200cm.The average WUE of field pea under NTS cross years was 15.8%,17.3%,10.3%,5.4%and 9.2%higher than that of T,NT,TS,TP,an NTP,respectively.The average WUE of spring wheat under NTS cross years was 0.6% lower than that of TP,and 15.6%,16,7%,12.6%and 0.8%higher than that of T,NT,TS and NTP,respectively.Improved soil structure arised from no-tillage and stubble retention can enhance water infiltration,reduce runoff and increase topsoil water content,hence improve soil physical quality.4) Soil fertilizer quality can be improved by the two stubble retention systems

Mots clés : Loess Plateau, No-till, Stubble retention, Plastic film mulch, Soil quality, Assessment system

Présentation (Dissertationtopic)

Page publiée le 21 avril 2013, mise à jour le 9 janvier 2018