Correlation Between Soil Water Retention Capability and Soil Salt Content

Pedosphere 10(3): 275~280, 20004422751ISSN 1002-0160/CN 32-1315/P回2000 SCIENCE PRES, BEIJINGCorrelation Between Soil Water Retention Capability andSoil Salt ContentFENG YONGJUNI, YANG JINGSONG2 and ZHENG JIUHUA1 College of Resource and Environment, Shandong Agriculture University, Taian 271018 (China)2 Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008 (China)(Received April 25, 2000; revised June 7, 2000)ABSTRACTThe soil moisture retention capability of Chao soil and coastal saline Chao soil in Shandong and Zhejiangprovincee were measured by pressure membrane method. The main factors infuencing soil moisture retentioncapability were studied by the metbods of correlation and path analyses. The results indicated that < 0.02mmphyaical clay and soil salt content were the main factors infuencing soil moisture retention capability. At soilsuction of 30~50 kPa, the soil salt content would be the dominant factor.Key Words; infuencing factor, physical clay, soil moisture retention capability, soil saltINTRODUCTIONSoil moisture is one of the main fertility factors directly affecting the growth and de-velopment of plants. Soil moiature is also the source of the water for all terrestrial plants(Yao, 1986). There is a close relationship between soil moisture retention capability and soilphysico- chemical properties such as mechanical composition, microaggregate, specfic surfacearea and organic matter content (Feng and Wang, 1992). However, litte quantitative analy-sis of soil salt effect on soil moisture retention capability has been found in published papers.In the present work soil moisture retention capability and physico-chemistry of Chao soil,coastal salinized soil and salinized Chao soil in Shandong and Zhejiang Provinces and theircorrelation were investigated to provide scientifc bases for soil improvement, field moisturecontrol and economic water utilization in agriculture.MATERIALS AND METHODSThe soil samples used in this study were Chao soil, coastal salinized Chao soil, salinesoil and continental salinized soil collected from Shouguang, Guangrao, Hekou, Lijin andBinzhou in Shangdong Province and Xiaoshan in Zhejiang Province, respectively. The sam-ples of each type of soil were taken from the surface layer of 0~20 cm and 20~40 cm. Soilorganic matter was tested by Walkley-Black wet oxidation method, soil mechanical com-position (based on international system) by hydrometer method (Institute of Soil Science,the Chinese Academy of Sciences, 1978), soil salt content by electric conductivity and dry中国煤化工MYHCNMHG276Y. J. FENG et al.evapotranspiration method (Rhoades and Ingvalson, 1971) and soil salt ions by routine de-termination method. Soil bulk density was measured by oven-drying method. Soil moistureretention capability was measured by presure membrane method at pressures of 10~30 kPa,30~50 kPa, 50~100 kPa, 100~300 kPa, 300~500 kPa, 500~1 000 kPa, and 1 000~1 500 kPa.RESULTS AND DISCUSSIONSoil suction for water absorption was caused by three factors: a) molecular attractionproduced by soil particle size or specific surface area; b) capillary force produced on water-airinterface in soil pore space; c) bydrophilic property and eletric property of soil colloid (Liuet al, 1985). But soil moisture, especially in salt-affected soil, was not pure water, becauseit constantly dissolves and carries many kinds of easily soluble salts (Kaddan and Rhoades,1976). In order to study the main factors that affected soil moisture retention ability, notonly moisture loss rates of diferent soils with diferent suctions (Table I) but also mainphysico-chemical properties (Table II) were measured. The results of correlation and pathanalysis are shown in Tables III and IV.TABLEIMcan moisture loss rates of diferent soilsSoil profleSuction (kPa)10~3030~5050~100 100~300300~500500~1 0001 000~1 500_%95H1016.8112.9010.722.250.320.7395H1028.3811.0412.822.500.690.0895H2017.548.425.723.892.380.480.8195H2027.2610.0812.445.930.850.520.8995H3016.569.8811.146.520.930.41.095H3025.828.8311.277.761.20.580.S95X02-13.056.683.411.990.771.5895X02-27.865.115.312.201.031.5295S003-15.707.529.445.170.650.9495S003-26.499.837.594.340.97.2195G01-18.565.957.304.651.352.3695G01-29.065.431.862.652.691.311.2795G02-119.004.985.992.861.001.1495G02-27.283.994.674.351.2695B01-17.323.954.902.876.362.161.2595B01-23.554.107.941.09.5595B02-18.093.474.213.631.9095B02-23.253.314.327.243.042.1495B03-18.938.046.615.400.9895B03-29.526.6712.800.530.5795B04-17.729.0217.391.10.9795B04-210.312.101.532.631.0695B05-16.895.101.880.861.5595B05-29.185.206.292.402.031.1895B06-19.114.782.661.961.9295B06-29.089.161.81 .2.891.221.30中国煤化工MYHCNMHGWATER RETENTION CAPABILITY AND SALT CONTENT277TABLE IIPhysical and chemical properties of the soilsSoil profleSaltOrganic matterMechanical composition< 0.02mm< 0.002mmgkg-1%95H1010.30.74421.164.0395H102 .0.637 .21.364.2395H2010.95424.595.0495H202).50.71925.225.4595H301.40.91049.619.9295H302).40.76549.249.7395X02-11.02843.1727.3695X02-2.60.90054.5628.8295S003-10.45532.7513.2295S003-20.64931.0612.9795G01-2).70.93359.5421.820.70.93059.1624.4895G02-10.40.82834.4622.0595G02-21.31053.3422.3895B01-125.01.42473.184.395B01-20.94992.378.36.095B02-17.01.61478.8813.0195B02-28.20.86590.956.6795B03-17.60.85147.465.5295B03-216.80.51828.883.4695B04-13.70.75128.848.1295B04-20.27518.6095B05-11.16246.2817.3295B05-20.59741.0116.8595B06-1.11,23048.4719.8095B06-20.84149.2720.36At a low soil suction (30~50 kPa), there were obviously negative correlations betweensoil suction (y) and the main soil physico chemical properties, including soil salinity (x1),organic matter (x2), < 0.02 mm physical clay (x3), and < 0.002 mm clay (zs), which couldaffect soil water potential; and the path coficint analysis showed that the path coeficientwas in the order ofx1 > x4> x3> 22 (Table II). It may be seen that when soil suction wasat 30~50 kPa, soil salt content was a vital factor infuencing soil moisture regime, and soilwater-holding capacity would rise if soil salt content increased. The decrease of soil moistureavailability was the key reason that soil salt infuenced the water suction and the growth ofcrops. If the amount of water is enough for the growth of crops, the irrigation norm in salinesoil should be larger than that of normal soil and irigation frequency should be increased(Bresler and Hoffma, 1986).When soil suction rose to 500~1 000 kPa, there was an sigificantly positive correlationbetween soil suction and < 0.02 mm physical clay, and the path coefficient was in the order ofx3>x1 > r4> x2 (Table IV). The results showed that when soil suction was at 500~1 000kPa, physical clay with a diameter < 0.02 mm would be the vital factor infuencing soil中国煤化工--MYHCNMHG278Y.J. FENG et al .TABLE IICorrelation coeficients and path coeficients between soil suction (u) at 30~50 kPa and some soil properties)(n= 26)T3c4yCorrelation cofficientE11.0000e20.1732t30.23730.610924-0.36680.29890.3581-0.6110-0.7318-0.4153SD0.88390.32050.46658.07073.4511Path coefficient对1-(z1~x4)-0.4981-0.0322- -0.0832- -0.1529z- (21~zs)- 0.1859-0.2143-0.1246别- (x1~x4)-0.1136-0.3507-0.1493 .四4 - (z1~z4)0.1827-0.0556-0.1256-0.4169)x1 - soil salinity, x2- organic matter, xa- < 0.02 mm physical clay, and 74- < 0.002 mm clay.TABLE IVCorrelation coefcients and path coeficients between soil Buction (y) at 500~1000 kPa and some soilproperties) (n= 26)工24Correlation coefficientx11.0001 00000 ,t40.28600.50400.73560.27010.4613Path cofficient四- (z1~zs)0.15510.01210.1487-0.02992- (x1~z4)0.02690.06980.38300.024423- (x1~xs)0.03680.04260.62690.02924 - (x1~x4)-0.05690.02090.22450816)z- Boil salinity, ng- organic matter, s- < 0.02 mm physical clay, and x4- < 0.002 mm clay.moisture, i.e., the higher the soil physical clay content, the greater the soil suction was. Athigh soil suction, soil physical clay and soil salt content were the main factors infuencingthe soil moisture availability. Those were the reasons why crops on saline soil would get tothe wilting coeficient earlier, which would cause the crop physiological drought and evendeath, in case of the same soil water content. The similar results were also obtained whensoil suction was at 50~500 kPa and 1000~1 500 kPa.The influence of the soil salt ions on soil moisture retention varied with the variety of theions. The infuence of the major salt ions, including Ca2+ (x1), Mg2+ (x2), K+Na+ (z3),so?- (x4), CI- (x5) and HCOz (xe), on soil water potential was studied at diferent suctions(y), and the results of path analyses are shown in Table V. The results of path analyses中国煤化工MYHCNMHGWATER RETENTION CAPABILITY AND SALT CONTENT279indicated that the path coefficients were in the orders of 25 > T3 > 21 > x4> x6> 22 atsoil suction of 30~50 kPa and x3 < s