Effects of Land Management Practices on Soil Water in Southwestern Mountainous Area, China

Available online at www sciencedirect.comAgricultural Sciences in ChioaScienceDirect2008. 7(7): 871-886July 2008Effects of Land Management Practices on Soil Water in SouthwesternMountainous Area, ChinaSHAO Jing-anl.2, WEI Chao-ful-and XIE De-til1 College of Resources and Environment, Southwest University, Chongqing 400716, P.R. China2 Geography Science Institute of Chongqing Normal University, Chongqing 400047, P.R. ChinaAbstractThe efectse of selected land management practices (cros sloping tllage, ridge culture, organic manure, and straw mulch)on soil water conservation in a southwestem mountainous area, China, were studied during November 2002 to November2004. The experimental field is divided into three parts based on soil layer dephs, 0-60 cm (part I), 0-40 cm (part I), and 0-20 cm (part I), and they all had the same slope azimuth (SE), slope (109), and slope type (linear). The experimental plotswere subjected to the fllowing treatments: cross sloping tllage (CST); cossloping tllage with organic manure (CST/OM); cross- sloping tllage with straw mulch (CST/SM); contour ridge culture (CRC); contour ridge culture with organicmanure (CRC/OM); and contour ridge culture with straw mulch (CRC/SM), to identify the effects of management practiceson soil water. Water contents were determined for soil samples collected, using a 2.2 cm diameter manual probe. Soil waterwas monitred once every five days from Nov. 20, 2002 to Nov. 20, 2004. The results indicated that, in the study stages,an integration of rainfall, evaporative losses, and crop transcription controiled the basic tendencies of profile (mean) soilwater, while land management practices, to a certain extent, only modified its amount, distribution, and routing. Moreover,these modifications also mainly focused on the first 20 cm depth of topsoil layer. When each management practice wascompared with control treatment, season changes of profile (mean) soil water were pronounced, while interannual changesamong them were not significant. More comparisons indicated that, in the study stages, contour ridge culture had bettereffects than cross-sloping tllage. And under the same tllage, the combination of organic manure could achieve more thanstraw mulch. These management practices should be recommended considering the effectiveness of soil and watermanagement techniques in the southwesterm mountainous area, China.Key words: land management practices, soil water, precision water management, southwestem mountainous area, Chinamean frost-free season of 270-363 days (Zhang et al.INTRODUCTION2004). It is generally considered that Chongqing issuitable for diversified crop growth. Yet, in this region,Water has become one of the most important resourcescrop production is under the threat from frequentfor Chinese agro-ecosystems in recent years.droughts. The sloping fields are the major land of crOPChongqing, located in the southwestern mountainousproduction, and cross -sloping tllage is a primary tllagearea, China, possesses unique agricultural climaticpractice (Luo et al. 2003). Moreover, the precipitationresources, e.g., annual mean temperature of 14.0-from April to September accounts for 50-80%, and19.0°C, annual mean precipitation of 1 00-1 200 mm,appe2003). Under-annual mean evaporation of 920-1 570 mm, and annual develd中国煤化工he low ailablilTYHCNMHGReccived 4 January, 2008 Accepted 30 April, 2008SHAO Jing-an, Ph D, E-mail: shaja@lreis ac cn; Correspondence WEI Chao-fu, E-mail: wcicf@swu.cdu.cn62008. CAAS Anghtsresorved Publishedby EsererLd.872SHAO Jing-aner al.of investment capital for ameliorating agricultural1 105.4 mm average annual rainfall, of which 70.0%irrigation and protecting soil from erosion. Up to now,occurs in the period from May to September, an annualonly 24.8% sloping fields are under irrigating (Luoevaporation of 1 220 mm, and an annual sunshineet al. 2003), and about 25.4% sloping fields underduration of 1276.7 h. The major natural disasters arewater and soil conservation measures (Qin 2000a).periodic drought or flood, and heavy water and soilSoil loss area is 63.3% of the total cover area, meanerosion. The soil at the experimental site is gray brownsoil erosion modulus is4 261 t km2 a:' (Tao et al.purple soil (Hapli-Stagnic Anthrosols in Chinese Soil2003). Drought probability is 80-90%, and mostlyTaxonomy) developed from the purple parent materialoccurs in July and August (Qin 2000b). Excessof Mesozoic Js. The dominant component of clayfertilizers, which are intended to compensate thesize fraction (<1 μm) is ilite. Fig.1 provided monthlydecrease of soil layer thickness and fertility due toprecipitation, sunshine duration and temperature valueswater and soil erosion, are applied tq ensure highrecorded in recent 30 years. Before setting up theyields, and consequently induce potentialexperiment, the area had been cultivated with wheatenvironmental impacts (Luo et al. 2003).(Triticum aestivum L.)-sweet potato (lpomoea batatasThe understanding of soil water contents underL.) rotation associated with corn (Zea mays L.)appropriate management practices may have profoundsuccession for 30 years under conventional cross-implications for agricultural water management. It issloping tllage with disking and ploughing.known that minimum tllage, n-tillage, and fallowingOne of the basic features of the sloping field in hillymay have a positive effect on soil water conservationareas is spatial variability of soil layer thickness. Soil(Hemnandez et al.2005; Moret et al. 2006). Surfacewater content is closely relative to soil layer thicknessstraw mulch and crop rotations can directly improve(Starr 2005). At the same time, slope azimuth, slopesoil water retention and reduce piping and surface runoffdegree, and slope type, to some extents, influence soil(Hartkamp et al. 2004; Hengsdijk et al. 2005).water content. Therefore, to truly reflect soil waterHowever, these research attentions have mainly focusedcontent of sloping field, and decrease measure errors,on arid, semi-arid, semi-humid regions, and lttle devotedthe field is divided into three parts based on soil layerto humid areas. The present paper is one part of an on-depth [0-60 cm (part I), 0-40 cm (part II), and 0-20going study on the precipitation resources uilizationcm (part I1), and they all had the same slope azimuthfor water saving agriculture in southwestern(SE), slope (10°), and slope type (linear), as shown inmountainous area of China. The intended 7-year study Fig.2. Soil properties of every part were described inwas initiated in November 2002. The data presentedTable. Every part was subjected to the samehere offers an exploratory analysis of the effects ofland management practices on soil water from November2002 to November 2004. The objective was to evaluateSunshine durtion50「Mean monthly lemperature1 35the impact of management practices on the soil waterof farming systems for precision water management int 3(00a humid area of southwestern China.2{ 2:s0|20EMATERIALS AND METHODS，1:Study site50 tThe experimental site, located in Sichuan Basin,southwesterm China (106926' E, 30°26" N; alt. 315-380中国煤化工101112“m), is a large hillside field (1.3 ha) with a slope of 10°MYHCNMHGapproximately. The climate is the subtropical humidFig.1 Mean monthly precipitation, sunshine duration andmonsoon with a mean annual temperature of 18.3°C,temperature in recent 30 yearrs.02008. CAAS. AIngnts reserved. Pubishedby EseverLidEffects of Land Management Practices on Soil Water in Southwestern Mountainous Area, China873management strategies.I m wheat or sweet potatolineManagement strategies0.5 m corm lineEach experiment plot (4 m x 5 m) was arranged in a↓m wheat or swcet potatolie|5complete randomized block experimental design with0.5 m com linetriplicate. A description of the plant patterms of sarmplingpoints was shown in Fig.3. 4 m longitudinal plots was1 m wheat or sweet potaolieplotted by five parts, involving three wheat or sweetpotato lines with 1 m width, and two corn lines withm.州0.5 m width. The row spacing of wheat was 0.2 m,and the distance between clusters was 0.15 m. TheFig. 3 The plant pattems of sampling points.row spacing of corn was 0.25 m, and the distancebetween clusters was 0.2 m. Thus, in every plot, 396clusters of wheat and 100 clusters of corn were planted.potato was grown. The row spacing of sweet potatoEvery cluster wheat included 4 individual plants, andwas 0.25 m, and the distance between clusters wasevery cluster corm involved 2 individual plants. After0.25 m. Hence, there were 240 individual sweet potatothe harvest of wheat, the field was ploughed, and sweet plants in every plot.Crosssloping tllage (CST) As control plot, in Sep-tember of every year, the field was conventionallyploughed at 18 cm depth followed by harrowing oncealong contour line, and chemical fertilizer was appliedat 125 kg ha:' urea [CO(NH2)], 100 kg ha' potassiumchloride (KCI), and 750 kg ha' lime superphosphate望一7三和[Ca(H,PO)2], thus the plot was divided. In October,λthe wheat was grown. When the wheat was ripe, thecom was grown. After the harvest of wheat, the fieldwas ploughed again, the chemical fertilizer was appliedLegendat 75 kg ha:' urea, and 900 kg ha' lime superphosphateSampling point[Ca(H,POJ)], and the sweet potato was grown.川中三”Contour lineCross-sloping tllage with organic manure (CST/Note: Verical inerval is I meterOM) The cross-sloping tllage method, the chemicaln lhis diagram.AB: Theamcnt scnal number. includngfertilizer application, and plant patterns were made asureatment A and replcaton B.CST. Cattle manure (20 000 and 20 000 kg ha',respectively) was applied, before the wheat and com wasFig. 2 The distribution of sampling point.grown.Table Chemical and physical properties of soil at 0-20 cmPart_pH__ Clay(%)OM(g kg)Total N(gkg"P_ Avalable N (mg kg”_ Available P (mg kg+) Available K (mg kg 1”6.10.3615.450.8923.414.2128n5.8.013.800.7712.211.31166.748.20.617.010“Dry combustion method.中国煤化工'Kjeldahl method.”Dfuse and absorbable method.TYHCNMHG“0.5 M NaHCO, extraction.”1 M NH.OAc extraction.02008.CAAS. AInghts reree PublshebyeEsevielud874SHAO Jing-an et al.-- CST-十CST/OMand furrow were 55 cm. The ridges were 25 cm wide- CRC/OMCRC/SMat the top and the furows were 30 cm wide and 35 cmCST/SM*- CRCdeep. The chemical fertilizer application and plant pat-- STDEVRainfallterns were made as CST.The same as below.Mean soil water (2002 2003)Contour ridge culture with organic manure (CRC/0OM) The ridge culture method was made as CRC.VV7T7~ VThe chemical fertilizer application and plant patterms30 t4Cwere made as CST. The application method of cattle25女manure was made as CST/OM.Contour ridge culture with straw mulch (CRCISM) Theridge culture method was made as CRC. The chemical言.15|120:fertilizer application and plant patterns were made as CST.10 tThe mulch method of rice stubble was made as CST/SM.60200Data measureThe soil was sampled in natural depth below the surface.Date (mon-d)The soil water was determined gravimetrically in theMean sol water (2003-2004)35samples obtained at depths of 0-5, 5-10, 10-20, 20-30,30-40, 40-50, and 50-60 cm for part I, 0-5, 5-10, 10-304020, 20-30, and 30-40 cm for part II, and 0-5, 5-10, and2:10-20 cm for part II, using a 2.2 cm diameter manual点2(. 80probe. Soil water was monitored every five days fromNov.20, 2002 to Nov. 20, 2004.I5| 1201Data analysis态内的特在的共200Data (measured or calculated) were subjected toANOVA, and mean values were separated usingDuncan's new multiple range test (DMRT) atDate (mon.d)P< 0.05. Standard deviations were calculated formean values of all the determinations. All statisticalFig. 4 Profle mean soil water of 0-60 cm depth in 2002-2003 andanalyses were performed with SPSS statistical2003-2004. CST, cross-sloping tllage; CST/OM，cross-slopingpackage.tllage with organic manure; CST/SM, cross-sloping tllage withstraw mulch; CRC, contour ridge culture; CRC/OM, contour ridgeculure with organic manure.RESULTS AND DISCUSSIONCross sloping tllage with straw mulch (CST/SM)Profile mean soil waterThe cross-sloping tllage method, the chemical fertil-izer application, and plant patterns were made as CST.Seasonal changes in the effects of land managementAfter the wheat was grown, rice stubble (50-60 cm,practices on profile mean soil water Figs.4-6 showed10 000 kg ha") was covered on the wheat.thatrent soil depths wereContour ridge culture (CRC) Ridge culture was per-disc中国煤化工s: rposel priodsformed throughout the year. Ridges were made within sprYHCNMHGodsinsummerandintervening furows in the fields, and the widths of ridgeautumn. Moreover, these pictures were the intervals02008. CAAS Arnghts rseved PtulshedbyElevertdEffects of Land Management Practices on Soil Water in Southwestern Mountainous Area, China_87Mcan soil water (002-2003)Mean soil water (2003-2004)35，03040252(80言1520120豆富”101160口200Date (mom-d)Dale (mom-d)Fig. 5 Profile mean soil water of 0-40 cm depth in 2002-2003 and 2003-2004.Mean soil water (2002-2003)Mean soit water (2003-2004)3:0g 2x12060，1605星昌尽昌员寻勇昌员垦学垦垦Date (mon-d)Fig. 6 Profle mean soil water of 0-20 cm depth in 2002-2003 and 2003-2004.of peaks and valleys. Comparisons were made amongharvested. Fluctuant periods were just about the wet0-20, 0-40, and 0-60 cm, and the results found that theperiods, during the period evaporation capacity and cropfluctuant degree of profile mean soil water ranked 0-60transpiration were both much higher, due to highcm < 0-40 cm <0-20 cm. Namely, 0-60 cm profiletemperature and most of crops being in the period ofmean soil water had lower fluctuation, while the reversegrowth. Certainly, thicker soil layer had favorableresults were recorded at 0-20 cm depth. Soil waterinfilration and antievaporation. Hence, the results couldcontents were closely relative to rainfal, evaporativebe explained by rainfall, evaporation, and croplosses, and crop transpiration. In the study site,transpiration corresponding to seasons and soil layerreposeful periods were mainly the dry periods of a year,thic中国煤化工:oupling efets ofduring this period, evaporative losses and croprainfEtranspiration largelytranspiration were also much lower, because of low aircontrMHc N M H Grile mean soil watertemperature and most of crops had not been grown orin humid areas. Similar results were reported by●2008. CAAS AInghts reserved. Publishedby Eseverud.76_SHAO Jingan et al.Hernandez et al. (2005) who described the effects ofcurred in the remaining periods. The effects of man-management practices on soil water conditioned byagement practices on profile mean soil water also tookrainfall (normal periods, wet periods, and dry periods).on remarkably temporal differences. This result wasHowever, more detailed comparisons among 0-20,consistent with the findings by van Lanen et al. (1992),0-40, and 0-60 cm, indicated that the effects ofwho found that the effects of soil management sys-management practices on profile mean soil water intems on soil water presented stronger temporal2002-2003 and 2003- 2004 had more similar trends. variability. Two-year successive organic manurePairwise comparisons of the peaks from the three soilapplication, straw mulch, and ridge culture favorablydepths corresponding to the periods showed that 0-60improved soil structure, thus holding more soil water.cm peaks were the sharpest, followed by 0-40 cm depthMoreover, larger rainfall (1 115.3 mm) than that ofpeaks, and the lowest peaks were 0-20 cm depth,the periods corresponding to 2004 (849.7 mm) wasespecially in wet periods. However, when comparedone of the primary reasons. Therefore, monthly rainfallwith the valleys corresponding to the periods, it wasshould be recorded at the time of soil water determi-found that 0-20 cm valleys were the deepest, followednation in the study site. As for CST, during Nov. 20,by 0-40 cm valleys, and the shallowest was 0-60 cm2002 to April 15, 2003, profile mean soil water wasvalleys. These results indicated that 0-20 cm profilehigher than that of the same treatment during the peri-mean soil water was more strongly affected by rainfall,ods corresponding to 2003-2004. This result sug-evaporation, and crop transpiration than that of 0-40gested that profile mean soil water could be deter-and 0-60 cm depths, due to relatively thin soil layer. Inmined by complicated factors, thus presenting stron-the wet periods, 0-20 cm soil depth had lowerger uncertainty.precipitation storage efficiency, while in dry periods,However, the interannual differences of 0-20, 0-40,even in normal periods, it was still short of the supplyand 0-60 cm profile mean soil water were not significant,of deeper soil water. 0-20 cm layer in higher temperaturewhen comparisons were made in the same treatment.seasons could not preferably protect soil water fromAs mentioned above, in humid area, it was hot withevaporation. Crops grew hard in 0-20 cm depth inhuge rainfall in summer and autumn, and cool withnormal periods, despite the distributions of most of cropobvious temperature difference and relatively low rainfallroots were not exceeding this depth. However, 0-40in spring and winter, indicating that profile mean soiland 0-60 cm soil depth had greater water retention andwater was subjected to the integrated effects of rainfall,antievaporation than 0-20 cm. In dry periods, the deeperevaporation, and crop transpiration. For 0-20 cm depth,layer soil water, to some extent, could replenish theit was very important to catch the temporal variationssurface soil water and thus, meeting the demand forof profile mean soil water for maintaining the normalcrop growth. At 0-20 cm depth, soil profile waterdemand for crop growth. In other words, lowervalues were noted to be lower than that at 0-40 and 0-variations would produce the greater effects on 0-2060 cm. Therefore, for 0-20 cm depth, it is imperativecm depth, while for 0-40 or 0-60 cm depths, theseto develop management practices that can help maintaineffects could be much less. Therefore, in terms of soila favorable soil water regime for crop growth as welllayer depth, it noted that proper management practicesas conserve the soil.were more efficient to avoid evaporation water into theInterannual changes in the effects of land man-atmosphere, and to increase rainfall infiltration.agement practices on profile mean soil water WhenDifference comparisons of the changes in the ef-the interannual changes of profile mean soil water werefects of land management practices on profile meancompared from the three soil depths, the obvious dif-soil water In contrast to CST, significant effects offerences were detected. In contrast to 2002-2003, pro-management practices on profile mean soil water werefile mean soil water from each management practice,detec中国煤化工「and autumn.except for CST, was generally lower during Nov. 20，Neverere stronger at 0-2002 to April 15, 2003 than that of the periods corre-20 cml:MYHc N M H Gthe peido(Fis.sponding to 2003-2004, while the reverse results 0C~ 4-6). Generally, other management practices versus02008. CAAS AInghts resesed PubishedbyEeverLIdEfets of Land Management Practices on Soil Water in Southwestern Mountainous Area, China877CST had 8.0-47.6%, 4.7-39.8%, and 3.4-32.4%to soil. The decomposition of straw improved soilgreater profile mean soil water at 0-20, 0-40, and 0-60structure, as a result, further increased profile soil watercm, respectively. Hence, proper management prac-storage. Cattle manure application, to a larger degree,tices could obtain better results at 0-20 cm than at 0-40enhanced the contents of SOM, thus could hold moreand 0-60 cm. For 0-60 cm depth, significant differ-profile soil water.ences among these effects were scarcely foundAs for 0-20 cm depth, the effects of management(P< 0.05), with the range of 3.0-6.0%, even somepractices on profile mean soil water were more complex.differences were more than 10.0% (Fig.4), indicat-In the study stage, profile mean soil water was 4.0-ing that, as for 60 cm depth soil layer, management16.0% greater in contour ridge culture than in cross-practices were not very efficient in holding moresloping tllge, except that it was in average 3.0-12.0%profile mean soil water. Certainly, the errors inlower in CRC/SM than in CST/SM. The processes interms of profile mean soil water examined in thewhich contour ridge culture with straw mulch influencesfield might not be avoided, due to the disturbances ofon 0-20 cm profile mean soil water are highlyenvironment factors. As we know, 60 cm depth soilcomplicated, and sometimes may even contradict tolayer could completely satisfy the demand of cropone another. For the same cross -sloping tllge, cattlegrowth. Moreover, a protective mesh would form withmanure application, in terms of profile mean soil water,the successive crops growth, thus no severe soil ero-achieved sound effects than straw mulch. CST/OMsion occurred and precipitation infiltration rate was sig-held average of 6- 10% greater profile mean soil waternificantly increased. In the study site, frequent rainfallthan CST/SM. Under contour ridge culture, thecan adequately compensate the reduced water avail-combination of cattle manure also gained 5.0-15.0%ability due to evaporative losses and crop transpiration, higher profile mean soil water than straw mulcheven in drought periods. Therefore, for 0-60 cm depth,application. For the same cattle manure application,the differences among the effects of the measures onthe effects of contour ridge culture on profile mean soilprofile mean soil water contents were much lower.water were obviously better than cross-sloping tllge.These results contradicted with those found in arid orCRC/OM had 10.0-27.0% greater profile mean soilsemiarid areas, where different management practiceswater than CST/OM. Contour ridge culture with organicobviously influence profile mean soil water contentmanure, to some degrees, improved soil microrelief and(Gicheru et al. 2004; Aboudrare et al. 2006).microenvironment, consequently, overland runoff wasAt 0-40 cm depth, higher mean water values in theheld up and rainfall infiltration was enhanced. Hence,soil profile were recorded for contour ridge culture thanat 0-20 cm depth, contour ridge culture with organicfor cross-sloping tllage. Generally, profile mean soilmanure was a more efficient management practice towater was 9.0-13% higher in contour ridge culture thanhold more soil water.in cross-sloping tllage. Ridge culture increased rainfallinfiltration, ridge ditch intercepted overland runoff,Profile soil waterchessom structure favored rainfall infiltration. Thisresult was consistent with Yang et al. (2005), who foundSeasonal changes in the effects of land managementthat ridge culture was an efficient method of waler practices on profile mean soil water Profile soil waterstorage. Moreover, for the same cross-sloping tillagedetermined at the seven depths presented a complicatedor ridge culture, profile mean soil water had not greaterpicture with the intervals between peaks and valleys, asdifferences among different management practices. Inshown in Figs.7-9. Generally, the peaks took place inhumid area, the effects of organic manure on profilerainy days, and the valleys distributed in post-rainy days.mean soil water in the same tllage methods were similarThe peaks were closely relative to rainfall capacity,to those obtained by physical mulch. This result wasrainfa中国煤化工e deep vlleys andsimilar to Jin et al. (1999) in Heilongjiang of China.shalloor short period ofStraw mulch reduced solar energy by physical mesh,post-rYH. CNM. HGied coparisonsand condensed some soil water vapor, thus returning itbetween peaks and rainy days for the seven depths0008,CAS. Anghseve. PuieshbyEyseverere.878SHAO Jing-an et al.0-5 cm (2002 2003)0-5 cm (003-200)353S030t4402520I0 官。151B16”16-」20Date (mon-d)5-10 cm (002003)5-10 cm (003-004)3(。20三1s劳120复富”10.16160于200Dale (mond)Dale (mon-d)10-20 cm 2002-2003)10-20 cm (003-200)VVV7得80复29t120夏15120信s可20中国煤化工I)ate (mon-)MHCNMHGoninued on next page)Fig. 7 Profile soil water of 0-60 cm depth in 2002-2003 and 2003-2004.0200B. CAAS Alnghts reserved Pubhshedby EIsevierLod.Effects of Land Management Practices on Soil Water in Southwesten Mountainous Area. China87920-30 cm (002-2003)20-30 cm (003-200)35 rVV~ TNV30个30 t15 ta15}1200t60u李e200Date (mon-d)Dale (mon-d)30-40 cm (2002-2003)30-40 cm 2003-200)0VT30 tx0富20 夏200 t也地在内地空在大大Datc (mon-d)40-50 cm (002-2003)40.50 cm (003-200)35 p，0VV T4(40525 t警I20盖夏中国煤化工MHCNMHGFig. 7 (Continued from the preceding page)02008, CAAS. nghtreseve. Pbishedby EsevierLtdSoil waler (%)Soil water (%)。Sol water (%)出11-20詩12-201-202-203-204.204-205-205-20 .6-207-207.20世8-209-2010-2011-.20g曾否5sRainfall (mm)Ranfall (mm)Soil waler (%6)管e1.20母+2Z.|困s.20? |海6.2工室8.2010-20 .员Effeets of Land Management Practices on Soil Water in Soulhwestern Mountainous Area, China88110-20 cm (002003)10-20 cm (003-2004)0so4(0β80 .1200t60o薛转内中英ht 200Datle (mon-d)Dalte (mon-d)20-30 cm (002-2003)20-30 cm (003-004)7V304025e2言120是200lArA20Datc (mon-d)Date (mon-d)30-40 cm (202-2003)30-40 cm (03-200)VT2s25上D富20秀0[Wot博在2000中国煤化工Dule (mon-d)MHCNMHGFig. 8 (Continued from the preceding page)02008. CAAS Alrights rsaed Puiheleseleree882SHAO Jing-an et al.0-5 cm (002-2003)0-5 cm (0-200035VV0304088复1520 520。046000Dac (mon-d)Date (mon-d)5-10 cm (00220305-10. cm (003-00)2580冒80120室富2010{ 1601f200Date (moo-d)10-20 cm (2002-2003)10-20 cm (003-200)VV~1200。160200纳者有荣本奉本本时200中国煤化工D)ale (mon-d)MHCNMHGFig. 9 Profile soil water of 0-20 cm depth in 2002-2003 and 2003. 2004.02008. CAAS AlInghs rseved Publshedby EseverLsu.Effects of Land Management Practices on Soil Water in Southwestemn Mountainous Area, China883revealed an overall greater similarity in profile soil water,cm depth. Hence, soil water contents for this layeri.e., around 78.6% peaks occurred in rainy days, onlyheavily changed due to the coupling effects of rainfall,21.4% peaks were in divergences. Deep valleys inevaporation loss, and crop transpiration. In contrast toprofile soil water almost presented in post-rainy days.0-20 cm depth, the degree of compaction of 20-40 cmAt the same time, higher water values in soil profilesoil depth was much higher. The changes in soil waterwere recorded in summer and autumn for a year, whilecontents for 0-20 cm depth was still closely relative tolower values were also detected in these periods. Therainfall, because the layer in 0-20 cm had soundreasons for these differences were that, in summer andpenetrability; but, in the layer of 20 40 cm depth, theautumn, rainfall, evaporative losses, and croprange of variation in soil water was lower than that oftranspiration were much higher, and the weather0-20 cm depth. Due to feeble evaporation and cropchanged frequently. Similar to profile mean soil water,transpiration, water from rainfall penetrated the layerprofile soil water could be also divided into reposefulof 0-20 cm and eventually was stored. During droughtperiods and fluctuant periods. It was noted that rainfallperiods, soil water from the layer of 20-40 cm wouldalso controlled the trends and processes of changes inmove upwards, and provided water for crop growth.profile soil water under the macro-environmentalIn 40-60 cm, the effects of rainfall, evaporation, andbackground. Comparing the peaks with valleys forcrop transpiration on soil water contents was muchdifferent soil deplhs, regardless of managementlesser. Only violent transpiration and in dry periods didpractices, the differences could be found from Figs.soil water from this layer exert some adjusting function7-9. Namely, the peaks for profile soil water from 0-on crop growth, because of its stronger stabilization.20 cm depth were sharper than from the other depths,Pairwise comparisons of the effects on profile soil waterand the valleys from this soil depth were deeper. by management practices disclosed that the soil waterHence, in the study site, profile soil water from 0-20tendency of the same soil depths, namely in 0-20 cm,cm layer was more sensitive to the weather changes0-40 cm, and 0-60 cm, were in accordance with thethan that from others. Pan and Shangguan (2004)relative periodsalso found that the variations of profile soil water areCompared with 0-40 and 0-60 cm, the peaks of 0-much greater in 0-20 cm than in 20-40 cm depth.20 cm were higher and sharper, while the valleys wereWhen the soil water contents from different soilalso deeper and sharper, suggesting that profile soilprofiles were compared, three pronounced stratificationswater, to some degrees, was subjected to circumstancewere observed regardless of management practices:factors. Namely, profile soil water would presentvertiginous stratification (0-20 cm), active stratificationuniform trend under the same environmental conditions,(20-40 cm), and stable stratification (40-60 cm). Thisregardless of soil layer thickness. Hence, environmentalresult was coincident with those obtained by Kongfactors controlled the essential direction of profile soilet al. (2005) from soil water dynamic of severalwater.species of shrubs in eastern mountainous areas of Inteannual changes in the effects of land manage-Heilongjiang, China. At 0 20 cm depth, profile soilment practices on profile mean soil water In thewater sharply changed with the alternations of dry-same soil depth, the interannual differences in the ef-wet periods, and it had significantly larger variationfects of management practices on profile soil waterthan at other depths. 0-20 cm depth was the dominativewere not pronounced, when pairwise comparisons wereinterface and root zone, maintaining soil-plant-made in the study stages (Figs.7-9). In the study site,atmosphere continuum (SPAC). Rainfall firstly enteredthe effects of management practices on soil water for0-20 cm soil depth via crop canopy and ltter layer, and0-20, 0-40, and 0-60 cm depths were similar in differ-then gradually infiltrated deep to soil layer. And cropent periods. In recent 30 years, rainfall data showedroots also mostly distributed in this layer, thus cropthat the中国煤化工eed tendays. Fortranspiration being very tempestuous. In higher0-40 aCNMHGcould be replen-temperature seasons, evaporation loss of soil water wasished trivugu I aiiiail, CVCIi 1 (drought periods.a primary factor affecting soil water contents for 0-20Moreover, the distributions of crop roots were not in02008. CAAS Alnghts reve Publishedby Eleverd.884SHAO Jing-an et al.excess of 20 cm soil depth. At the same time, soilof water supply (rainfall) and water loss (evaporationwater below 20 cm could replenish surface water loss.and crop transpiration), the effects of managementUnder such circumstances, opposite to CST, differentpractices were not very obvious. As for 0-60 cm layer,management practices had similar effects to hold soilthe management practices are highly promising for thewater, even in serious drought periods. These resultsfight against soil water loss than for 0-20 cm layer inwere contrary to Yang et al. (2005), who thought thatsummer and autumn.ridge culture with straw mulch favored storing moreDifference in comparisons of effects of land man-water in agrigrazing ecotone; but were consistent withagement practices on profile mean soil water Com-Yu et al. (2004), who considered that, despite that theparing the effects of management practices on profleeffects of straw mulch on saving water were not sig-soil water from 0-20, 0-40, and 0-60 cm, it was foundnificant in humid periods, straw mulch had significantthat the differences were very pronounced (Figs.7-9).effects on saving water of the surface soil (0-20 cm),For 0-60 cm depth, these differences mainly occurredespecially in the early growth period of crops. Inat the first three depths, 0-5, 5-10, and 10-20 cm, andgeneral, straw mulch, ridge culture, or ridge culturethe differences were scarcely detected below 30 cm,with straw mulch were considered as the efficient mea-as shown in Fig.7. For 0-40 cm depth, the effectssures to store soil water. But, in humid area, by com-were stronger than that at corresponding depths of 0-parisons of their effects on profile soil water, the dif-60 cm, and that they primarily happened at 0-20 cmferences were not significant due to frequent rainfall.depth. 0-40 cm profile soil water in CST was in aver-However, in 0-20 cm depth, the profile soil waterage 3.0-42.7% lower than that under other manage-was, to a great extent, influenced by the couplingment practices, especially at topsoil layer (0-20 cm).functions of rainfall, evaporative losses, and cropStraw mulch, to a larger extent, weakened solartranspiration, due to the thinner soil layer. During wetradiation, adjusted soil temperature, and further re-periods, this soil layer had the lowest water storagestrained evaporative losses. Water vapor was returnedcapacity, and the anti-drought ability was much weakerto soil in the form of condensation water, due to meet-in dry periods. As shown in Fig.9, the effects ofing with straw mulch. Straw mulch and cattle manuremanagement practices on 0-20 cm profile soil waterapplication also enhanced retention ability of soil waterhad not remarkably interannual difference. For 0-40and saving water, and decreased the opportunity ofand 0-60 cm depths, only in the first 20 cm depth,water loss from soil to atmosphere. These practiceswhen the effects of management practices on soil wateralso increased soil organic matter (SOM) contents, andin different seasons were compared, greater effectsimproved soil structure, thus declining soil capillarywere found in summer and autumn; lower effects wereporosity. Ridge culture ammeliorated soil microrelief,detected in spring and winter. Moreover, the degree ofand headed off overland runoff. Moreover, ridge cul-variation was significantly lower associating with soilture favored the amendments of soil structure towardsdepths. This result indicated that profile soil water waschessom, and removed the functions of gravitationalclosely relative to profile mean soil water. In summerwater. Under ridge culture, the capillary hydrologicaland autumn, despite much heavier rainfall, thesystem in dominative state would lead to the decreasedevaporation and crop lranspiration were greater as well,soil water loss. Ramos and Martinez-Casasnovasdue to higher air temperature and crops being in growing(2006) obtained the consistent results from the impactseason. Under such circumstances, managementof land levelling on soil moisture and runoff variabilitypractices were very important, which formed aunder different rainfall distributions. Nevertheless, allprotective mesh against profle soil water losses. Guoof these management practices also mainly operated atet al. (2005) found similar results, that the effects of0-20 cm depth, but not below 30 cm.conservation tllage on soil water were more obvious in中国煤化Iwere much strongersummer and autumn than in spring and winter. In springthanf 0-40 and 0-60 cm.and winter, rainfall was lesser with lower evaporationAt0YH.CNMHGasinaverge12.0and crop transpiration. Under the coupling functions53.0% greater, when other treatments were compared02008. CAAS AlInghts esened Pubished by EsewerLdEffects of Land Management Practices on Soil Water in Southwestern Mountainous Area, China885with CST; while at 5- 10 cm depth this number wasdepths, respectively.11.0-38.0%. In southwestemn mountainous area, China,thinner soil layer strongly limited agricultural production.CONCLUSIONAs previously indicated, profile soil water was closerelative to thickness of soil horizon. Thicker soil layer Consevation of soil water is an important managementretained more soil water, especially in drought periods.objective for crop production in humid mountainousIn summer and autumn, when evaporation and croparea, China, where season droughts are frequent. Intranspiration were higher, the application of managementthis study, the response of profile (mean) soil waterpractices could obtain sound effects to hold more soilcontents to management practices was very clear. Landwater. But, the effects of management practices onmanagement practices, to a certain extent, only modifiedprofle soil water mainly happened at 0-20 cm layer.ts amount, distribution, and routing. And theseEvaporation and crop transpiration primarily occurred atmodifications also mainly focused on the first 20 cmsurface soil. Only in serious drought periods did soildepth (i.e, topsoil layer). For the same managementwater form deeper soil layer can supply surface soil waterpractices, the season changes of profile (mean) soilthrough moving upwards. Al the same time, profle soil water were pronounced, while interannual changeswater presented an increasing trend along the 0-20 cmamong them were not significant. The use of cross-soil depths, regardless of management practices. Thatsloping tllage and contour ridge culture together withis, profile soil water showed certain spatial variation.cattle manure and straw mulch significantly improvedMoreover, crop roots also mostly distributed in 0-20 cmsome profile (mean) soil water characteristics. Moresoil layer. Therefore, it was very necessary to adoptcomparisons indicated that contour ridge culture hadproper management practices for maintaining more soilbetter effects than cross-sloping tllage. Under the samewater. Otherwise, slopeland agricultural production wastillage methods, the combination of organic manuremore difficult, especially in drought periods.could obtain better results than straw mulch. It may beWhen profile soil water contents were comparedwise to make use of these approaches to conserve andunder different management practices, cross-slopingstore soil water in the southwestern humid area, China.tillage had generally lower profile soil water than contourridge culture, but the contrary result was detectedAcknowledgementsbetween CRC/SM and CSR/SM. Moreover, theseThe project was financially supported by the Cultiva-differences presented lower spatial-temporal variation.tion Fund of the Key Scientific and Technical Innova-This result showed that different management practicestion Project, Ministry of Education of China (706049).had obviously different efficiencies, profile soil waterwas also closely relative to profile mean soil water. 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Conservationachieved better effects than straw mulch application.tilge effects on soil moisture and water use efficiency ofThus, CST/SM had 8.0-22.0%, 5.0-14.0%, and 3.0-中国煤化工8 wheat and field pea16.0% lower profile soil water than CST/OM, similarly,MHCNMHGConsernation, 19, 165-CRC/SM had 8.0-32.49%, 10.0-24.0%, and 17.0-30.0%lower profile soil water than CRC/OM, in the threeHartkamp A D, White JW, Rossing W A H, van Itersum M K,●2008, CAAS Algts re PutishedyEseverld.886SHAO Jing-an er al.Bakker E J, Rabbinge R. 2004. Regional application of aQin Z Y.2000a. Analysis of major weather disaster in Chongqing.cropping systems simulation model: Crop residue retentionJournal of Soulhwest China Normal University (Naturalin maize production systems of Jalisco, Mexico. AgriculturalScience), 25, 78-85. (in Chinese)Systems, 82, 117-138.QinZ Y. 2000. Researches in dividing regions of the integrativeHengsdijk H, Mejerink G W, Mosugu M E. 2005. Modeling thenatural disaster in Chongqing. 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Chinese Journal of Applied Ecology, 15, 2061-2066.in hlly areas of Sichuan, China. Soil and Tllge Research,(in Chinese)75, 99-107.(Edited by ZHAO Qi)中国煤化工MYHCNMHG2008, CAAS Alnghs rseve Pubishedby EserLtd,.