Effects of Combined APPlication of Water Retaining Agents and Organic Materials on Water Holding Characteristics of Yellow Brown Soils in Hilly Areas

Yubang TANG，Lijun YP，Lei XP，Jia LPO，Dongsheng WANG，Ruqin FAN，Qin PEl

1.Agricultural FacilitY and Preparation Research lnstitution，Jiangsu AcademY of Agricultural Sciences，Nanjing 210014，China；

2.Resources and Environmental Research AcademY，Jiangsu AcademY of Agricultural Sciences，Nanjing 210014，China；

3.Nanjing Vegetable Research lnstitute，Nanjing 210042，China

Effects of Combined APPlication of Water Retaining Agents and Organic Materials on Water Holding Characteristics of Yellow Brown Soils in Hilly Areas

Yubang TANG1*，Lijun YP1，Lei XP1，Jia LPO2，Dongsheng WANG3，Ruqin FAN2，Qin PEl1

1.Agricultural FacilitY and Preparation Research lnstitution，Jiangsu AcademY of Agricultural Sciences，Nanjing 210014，China；

2.Resources and Environmental Research AcademY，Jiangsu AcademY of Agricultural Sciences，Nanjing 210014，China；

3.Nanjing Vegetable Research lnstitute，Nanjing 210042，China

［Objective］The aim was to reduce fertilizer and water losses caused bY surface runoffs in rainY season and provide scientific

for soil moisture in arid season. ［Method］The application proportion of complex water-holding organic materials was determined bY multi-factor mixture experiment and the curve changes of soil moisture characters were tested to analYze water-holding capacitY and water availabilitY of soils. ［Result］The initial moisture content of soil with different mixture proportions improved in varYing degrees.For example，when water-retention agents reached 0.4%and 0.6%of soil weight，soil moisture contents were 69.0% and 70.5%，respectivelY，which showed significant differences with the control（S0.0）.Soil dehYdration terms in different treatments all extended，prolonging in the range of 4.6-14 d.［Conclusion］The applications of water-retention agent and organic material would improve water-holding capacitY of hills and low mountains，and initial moisture content and dehYdration cYcle tend to be volatile upon mixture proportion.Therefore，it is necessarY to adjust soil fertilitY，crop species，and irrigation to meet crop demands on fertilizer and water.

Water retaining agents；Organic materials；Soils of hillY areas；Water characteristics

H illY slopes are extensivelY distributed in Jiangsu Province and the area of lands available for development reaches 600 000 hm2. Because of steep slopes in hillY areas，soil structure，water permeabilitY and water-retaining propertY perform poorlY and forests and grasses are sparselY distributed，with a low coverage rate［1-2］.ln rainY season，surface erosion and gullY erosion occur frequentlY due to effects ofsurface runoffs which are mostlY under evaporation，so that less water can be absorbed bY soils，let alone used bY plants［3］.After rains，however，surface soils would turn drY bY sunning，which is adverse for plant growth. Therefore，it is a primarY work to control water and soil losses in slope wastelands in hillY areas in order to increase infiltration rate of rain and improve soil fertilitY and phYsical and chemical structures.

CurrentlY，researches available are more on improving water of sandY soils bY using water-retaining agents，which enjoYs a promising prospect in tolerance of droughts，water holding，and increasing crop Yield［4-5］.Further more，it is reported that water-retaining agents is capable of holding water，absorbing fertilizer，as well as improving soilstructure，including increasing granules and enhancing air permeabil itY［6］.Nevertheless，less attention ispaid to improving water characteristics of soils with water-retaining agents in Yellow brown soils in hillY areas.

The research made use of organic materials dominated bY fermented biological fillers and starchbase/acrYlic acid series absorbents and conducted monitoring on water dY-namics in soils，on basis of fertilizer and water losses in hillY slopes in order to explore the effects of different proportions on water-retaining characteristics of soils and provide references for improving water and fertilizers in soils to improve crop Yield.

Materials and Methods

Test materials

The test soils were Yellow brown soils in hillY barren slopes in Hengxi Town，Nanjing CitY，Jiangsu Province. After natural withering，stones，roots and stems were removed and phYsical and chemical characters of soils in field E were shown（Table 1）.

ln the test，water-retaining agent was starch-base/acrYlic acid series super-absorbent resins；granularitY was in the range of 30-40 mu；absorbencY of deionized water was in 800-1 000 times（mass fraction//g/g）.

The test organic materials were fermented fillers of feedlots in Liuhe Animal Test Site，Jiangsu AcademY of Agricultural Sciences（Table 2）.

Test treatments

The doses of super absorbent polYmer（SAP）were 0%，0.1%，0.2%，0.4%and 0.6%of soil weights，represented bY S0.0，S0.1，S0.2，S0.4 and S0.6，respectivelY.

The quantities of organic materials were 0%，2.5%，5%and 10%of soil weights，represented bY F0.0，F2.5，F5.0 and F10.0，respectivelY，with three replications.

Methods

Testing of soil moisture suction and water retention caPacities of soils in different treatments The dried soils of 2 500 g were collected and placed to a test basin and moisture content of soil was measured as per oven drYing method，followed bY calculation of weights of dried soils.lt is notable that water-retention materials，organic materials and soils should be weighed strictlY according to test demands and well mixed.SubsequentlY，the test basin was placed into a water tank to absorb water for 24，but water surface should be lower than margin of the basin and soil surface. Then，the basin was collected and placed there to allow water to seep slowlY and the basin was weighed until none water seeped again.Besides，weighing and recording should be conducted regularlY everY daY.

Testing and analyzing of effects of water-retention agents and organic materials on curve changes of soil moisture characteristics The research designed 4 treatments，including treatment 1 of the control with soils from hillY barren slopes，treatment 2 with water-retention materials at dose of 0.4%of soil weights，treatment 3 with organic materials at dose of 10% of soil weights，and treatment 4 with water-retention materials and organic materials at doses of 0.4%and 10%.A tensiometer was inserted to soils to measure tensions of soil moisture in the basin.Neanwhile，soil weight was measured with an electronic weight sensor，and moisture content of soil was measured bY minusing，followed bY mapping curve of moisture characters of soils.

Table 1 PhYsical and chemical characteristics of barren slopes in hillY areas

Table 2 Basic phYsiochemical properties of organic materials

Table 3 The analYsis of significance of water changes in soils among treatments

Results and Analysis

Effects of different treatments on water-holding caPacity of soils of hilly barren sloPe

The test soils were Yellow brown soils from hillY barren slopes in Hengxi Town，Nanjing，and the barren slopes were in the range of 20-30°，with stickY soils and poor air and water permeabilitY.ln rainY seasons，runoffs are more，but less water are absorbed bY soils，not to mention utilized bY plants. Therefore，the research applied the mixture of water-retention agents and organic materials to increase infiltration rate and improve water movements in soils.Based on moisture measurement in 35 daYs，initial saturated water content，final water content，and dailY mean evaporation capacitY were taken as time nodes of water changes to analYze water retention capacitY and water holding capacitY（Table 3）.

As shown in Table 3，initial moisture content showed significant differences with final moisture content bY adding SAP and dailY mean evaporation capacitY of soil moisture also differed dramaticallY with that of control.

According to further analYsis onsoil moisture，initial moisture content of soil was increasing upon SAP doses，and when the doses reached 0.4% and 0.6%of soil weight，soil moisture content achieved 69.0%and 70.5%，which showed significant differences that of control（S0.0）.On the other hand，soil water suction and retention capacities were weakening upon organic materials and water retention capacitY of soil would be affected significantlY when organic materials reached 5.0%-10.0%of soil weight.lt can be concluded from Fig.1 that with onlY water-retaining agentapplied，initial moisture content of soil kept increasing upon SAP quantitY.lt is notable thatwater-retention materials and organic materials should be applied with consideration of soil fertilitY and crop demands.For example，it is recommended to applY 5%-10%organic materials and 0.4%water-retention materials for crops with higher demands on soil fertilizer，which is equivalent to single application of 0.2% water-retention agent while increasing soil fertilizers.

ln addition，as shown in Table 5， dailY mean evaporation capacitY in the treatment with water-retention agent was higher than treatment without water-retention agent，but still kept higher after 35 d，because of high initial moisture content（Fig.3）.Noisture content in S0.0 reduced bY 3%-5%，which means water shortage for most crops. ln contrast，moisture contents of S0.4 and S0.6 maintained bY 10%and 15%.

Table 4 The analYsis of significance on initial water content among treatments

Effects of aPPlication of water-retention agent and organic materials on curve of soil water characteristics

lt can be concluded from statistics and analYsis of final moisture content that moisture content of soil in S0.6 showed significant differences with that of S0.2，proving that the adding of water-retention agent will improve soil moisture suction and retention capacities.

As shown in Fig.5，when moisture content of soil was higher，the adding of water-retention agent increased soil absorption on free water and relative tension value kept increasing，also. However，when moisture content of soil declined to 16%，the tension value was decreasing，which indicated that water absorbed bY SAP seeped，plaY-ing the role of two-waYs regulation for micro-reservoir（Fig.4）.When moisture content of soil dropped to 15%in the control，soil moisture suction actuallY reached 63 kpa，which means water shortage for most crops.When waterabsorbing materials and organic materials were added，moisture content of soil decreased to 53 kpa，and binding force of soil on water declined，so that water available in soils increased relativelY bY crops（Fig.5）.

As shown in Fig.6，with water retention materials added，supplYing time of available water in soils would be extended.For example，it took about 640 h for soils in the control to reduce from saturation moisture content to soil water suction of 92.7 kpa，but 1 012 h if 0.4%SAP was added. As for soils added with 0.4%SAP and 10%organic materials，it took about 752 h to reach the same soil water suction，extending about 4.6 d for soils to supplY water.

Conclusion

The effects of integrated application of water-retention agent and organic materials tend to be volatile on soil water-holding capacitY upon mixture ratio.For example，saturated soil moisture contentkeeps increasing upon water-retention agent，but waterholding capacitY of soil would decline bY applYing organic materials.Therefore，it is necessarY to adjust mixture ratio of water-retention agent and organic materials according to crop growth characters to meet crop demands on water and fertilizer.

lt can be concluded from changes of soil moisture that mixture ratio of water-retention agent and organic materials has different effects on soil dehYdration term.For instance，the term extended in the range of 4.6-14 d. Therefore，it is necessarY to applY water-retention agent and organic materials at a proper proportion with consideration of irrigations to meet crop demands on water.

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ResPonsible editor：Xiaoxue WANG

ResPonsible Proofreader：Xiaoyan WP

保水剂与有机物料联合施用对丘陵黄棕壤持水特性的影响

唐玉邦1*，虞利俊1，徐磊1，罗佳2，王东升3，范如芹2，裴勤1（1.江苏省农业科学院农业设施与准备研究所，江苏南京210014；2.江苏省农业科学院资源与环境研究所，江苏南京210014；3.南京市蔬菜研究所，江苏南京 210042）

［目的］减少丘陵坡地雨季地表径流造成的肥水损失，增加干旱季节土壤墒情提供科学数据。［方法］通过多因子复配试验明确复合保水型有机物料的施用比例，对土壤水分特征曲线变化进行测试，分析土壤持水特性及水分有效性。［结果］不同复配比例处理的土壤初始含水量均有所提高，当保水剂用量为土壤重量的0.4%和0.6%时土壤含水量分别达到69.0%和70.5%，与对照（S0.0）相比有显著性差异。各处理脱水期都有所延长，与对照组相比（张力值92.7 Kpa时）脱水天数延长了4.6～14d。［结论］保水剂和有机物料配合施用可改善丘陵荒坡地土壤的吸水持水性能，调整复配比例可获得不同初始水分含量和脱水周期，可根据当地的土壤肥力情况、作物种类、灌溉条件进行复配以满足作物生长对肥水的需求。

保水剂；有机物料；丘陵土壤；水分特征

江苏省农业科技自主创新资金项目［CX（14）2099］。

唐玉邦（1959-），男，上海人，副研究员，从事设施种植环境监控研发工作，E-mail：tangyubang_007@sina.com。*通讯作者。

2015-07-06

Supported bY Fund for lndependent lnnovation of Agricultural Sciences in Jiangsu Province（CX（14）2099）.

*Corresponding author.E-mail:tangYubang_007@sina.com

Received:JulY 6，2015 Accepted:August 16，2015

修回日期 2015-08-16