Joongdae Choi, Chulhee Won and Dongkoun YunKangwon National University, Korea

Rural Research Institute, Korea

2012. 6. 27ICID 2012, Adelaide, Australia

Effect of rice straw mat and PAM application on runoff and lettuce production from steep sloped

sandy loam plots

Con-

tents

Results and Discussion

Methods and Material

Con-tents

Conclusions

Background and objectives

Background and Objectives

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I. Background

Rivers and lakes in Korea are clean and clear and maintain a good

water quality in general

During rainy season of June to August, muddy runoff from up-

stream regions where large scale vegetable farming is practiced on

sloping fields has created serious turbidity problems and threat-

ened aquatic ecosystems in downstream rivers and lakes

For example, muddy runoff in July, 2006 badly increased turbidity

more than 240 days in the North Han River because the runoff

stored in a cascade of dam lakes and discharged slowly to down-

stream

I. Background

The Korean Government designated the area as the prioritized soil ero-

sion and NPS pollution management area in 2007 to reduce soil erosion

and muddy runoff

Various structural best management practices (BMPs) were introduced

to the area

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Examples of Structural BMPs

I. Background

However, the effect of structural BMPs was not satisfactory because

they could not manage the source areas where the muddy runoff is

generated

And BMPs to manage and control soil erosion and muddy runoff are

required to develop and apply to the area

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Status of highland sloping fields - Intensive vegetable farming : potato, cabbage, radish, etc. - Conventional tillage : continuous disturbance of soil column - Sandy or loamy sandy soil : easy to erode by raindrop impact and runoff - High intensity rainfall in monsoon season - Very vulnerable to soil erosion

I. BackgroundConditions for the BMPs to be developed

- Minimize the impact of raindrop impact - Maximize infiltration of the soil - Reduce runoff and soil erosion - Minimize muddy runoff

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Alternatives for the BMPs - No-till practices - Contour tillage - Residue cover - Application of PAM and gypsum - Adoption of furrow dam - Combination of the above

I. Background – Preliminary Rainfall Simulation Studies

-A series of indoor rainfall simulation studies were conducted-Objectives : experimentally measure the effect of surface mulching materials on runoff and soil erosion-Surface mulching materials – combinations of rice straw, rice straw mat, PAM, and gypsum

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-Why rice straw for mulch? -Vegetable farming does not leave stable residues -More than 60% of farmland in Korea is rice paddy and rice straws are readily available -Experimental treatments -1, 2 and 3 layers of rice straw mat -Combination of rice straw mat, PAM, rice hull and sawdust -Combination of rice straw mat, PAM and gypsum

Experiment 1 - Mulching size - Control, straw mat 300, 600, and 900 g/m2

- Slope : 10%, 20% - Rainfall intensity : 30 mm/hr, 60 mm/hr - Simulation : 60 minutes Experiment 2 – Addition of PAM, sawdust,

chaff - Control, mat+PAM, mat+sawdust+PAM,

mat+rice chaff+PAM - Slope : 10%, 20% - Rainfall intensity : 30 mm/hr, 60 mm/hr - Simulation : 60 minutes Experiment 3 – Addition of PAM and gyp-

sum - Control, mat+PAM+Gypsum,

mat+sawdust+PAM+ Gypsum, mat+rice chaff+PAM+Gypsum

- Slope : 10%, 20% - Rainfall intensity : 30 mm/hr - Simulation : 60 minutes

System Components- 2 sets of Ladder-type rainfall simulator

developed in the USDA Soil Erosion Lab in Purdue University

-Soil boxes of 1x1x0.5 m-Controller, water supply system, crane

and other necessary systems - The system can simulate 20~100 mm/

hr rainfall

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I. Background – Indoor Rainfall Simulation System

Under 30 mm/h simulation

- As the size of mulching increased from 300 to 900 kg/ha, practically no runoff produced from both 10 and 20% slopes

Under 60 mm/h simulation

- Runoff reduced significantly. Reduc-tion rate of runoff increased as the size of straw mat mulching increased

Reduction rate of runoff (a) RI of 30 mm/hr and 10% slope, (b) RI of 30 mm/hr and 20% slope, (c) RI of 60 mm/hr and 10% slope, (d) RI of 60 mm/hr and 20% slope.

Results – Effect of Mulching Size (Exp. 1) on Runoff Reduction (%)

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Under 30 mm/h simulation - Runoff reduction was prominent. - SPR treatment showed the highest reduction of 98.7% Under 60 mm/h simulation - Runoff reduced significantly

Runoff, runoff rate and reduction rate of runoffSP=mat+PAM, SPS=mat+PAM+sawdust, SPR=mat+PAM+chaff

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Results – Effect of Mulching (Exp. 2) on Runoff Re-duction (%)

Under 30 mm/h and 10% simulation, runoff rate of SCPG ranged 0.2∼2.7 %., which meant that the average reduction was 98.7 % compared to that of control Under 30 mm/h and 20% simulation, average reduction rate of runoff was 81.7 %. Reduction of sediment discharge was also significant

Runoff rate (%) with respect to treatment. SPG=mat+PAM+Gypsum,

SSPG=mat+PAM+sawdust+Gypsum, SCPG=mat+PAM+chaff+Gypsum

Sediment reduction (%)

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Results – Effect of Mulching (Exp. 3) on Runoff Re-duction (%)

Results –Laboratory Rainfall Simulation Studies

- The experiments clearly showed that the mulching materials composed of rice straw mat, PAM, gyp-sum, sawdust, and rice chaff could significantly re-duce runoff and sediment discharges.

- It was also realized that although the addition of sawdust and chaff were effective in further reduc-ing runoff and soil erosion, it was not practically vi-able.

- And, field scale experiments to measure the effect of the mulching materials were required.

Reduce the runoff Manage the muddy runoffReduce

NPS Pollution

Objective

Experimentally measure the effect of surface mulching materials (s-

traw mat, PAM, Gypsum) on the reduction of runoff and NPS pol-lution from steep sloped experimental plots that are similar to highland agricultural fields

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Methods and Material

II. Methods and Materials

The size of a plot : 5 30 mⅩ Soil texture : loamy sand

Slope : 28%

Four experimental treatments

Lettuce was cultivated during a growing season in 2011

Runoff and other variables were collected under natural rainfall condition

C

Control

-No treatment

T2

PAM and Gyp-

sum

-PAM : 5kg/ha

-Gypsum :

1,000kg/ha

T3

Combination of

mat, PAM and

gypsum(T1 +

T2)

T1

Woven rice

straw mat

-567 kg/ha

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II. Methods and Materials

Rice straw mat

PAM and characteristics

Form Color OdorWater

solubilitySpecific gravity

pH (0.5% solution)

PAM Granular powder White

Little or no

Soluble 0.75 6∼9

Gypsum

II. Methods and Material

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C T1 T2 T3

Results and Discussion

Date Rainfall(mm)

Control T1 T2 T3

r r D(%) r D(%) r D(%)

6/23~27 205 0.014 0.010 25.0 0.010 27.7 0.000 100

6/29~30 203.4 0.052 0.042 17.6 0.042 19.4 0.016 68.3

7/3~4 77.6 0.164 0.094 42.3 0.103 37.2 0.018 88.8

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r : runoff coefficient, D : Reduction rate compared to control (C)

III. Results and Discussion

Rainfall event, runoff ratio and runoff reduction ratio in 2011

All treatments could effectively reduce runoff.

Treatment effect of T1 and T2 was similar but was quite lower than expected

However, the combined treatment (T3) of T1 and T2 showed dramatic increase in the

reduction of runoff. The treatment effect of T3 was more than doubled compared to

those of T1 and T2

It was concluded that T3, a combination of straw mat, PAM and gypsum, could be a

BMP to reduce muddy from sloping highland fields in Korea

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III. Results and Discussion

NPS pollution load and reduction ratio of the experiment

Date TreatmentNPS pollution load (kg) D (%)

BOD SS CODCr T-N T-P BOD SS CODCr T-N T-P

6/23~27

C 0.0017 0.7682 0.0191 0.0197 0.0019 - - - - -

T1 0.0007 0.2248 0.01 0.0116 0.0012 58.8 70.7 47.6 41.1 36.8

T2 0.0006 0.1328 0.0072 0.0091 0.0011 64.7 82.7 62.3 53.8 42.1

T3 0 0 0 0 0 100 100 100 100 100

6/29~30

C 0.0036 1.8799 0.0453 0.0199 0.0027 - - - - -

T1 0.002 0.1834 0.0208 0.0173 0.0008 44.4 90.2 54.1 13.1 70.4

T2 0.0032 0.5835 0.0199 0.0147 0.0014 11.1 69.0 56.1 26.1 48.1

T3 0.0006 0.0097 0.0051 0.0038 0.0002 83.3 99.5 88.7 80.9 92.6

7/3~4

C 0.0031 1.6828 0.0373 0.0408 0.0024 - - - - -

T1 0.0013 0.1428 0.0137 0.0203 0.0008 58.1 91.5 63.3 50.2 66.7

T2 0.0021 0.5692 0.0178 0.0268 0.002 32.3 66.2 52.3 34.3 16.7

T3 0.0003 0.011 0.0031 0.0035 0.0002 90.3 99.3 91.7 91.4 91.7

D : Reduction rate compared to control (C)

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III. Results and Discussion

Treatment effect of T1 and T2 on the reduction of NPS pollution load was accept-

able but lower than that of T3

Treatment effect of T3 was amazingly high, ranging from 80.9~100% reduction of

NPS pollution loads compared to that of control

It was concluded that T3 could greatly contribute to the improvement of turbidity

and other water quality in downstream rivers and lakes if it could be applied to the

sloping highland fields

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III. Results and Discussion

Yield of lettuce

- Control (C) : 140 kg

- Straw mat (T1) : 567 kg - PAM and Gypsum (T2) : 453 kg - Combined T1 and T2 : 1,067 kg

Yield of lettuce

Yield increase of lettuce

- Control (C) : -

- Straw mat (T1) : 400 % - PAM and Gypsum (T2) : 320 % - Combined T1 and T2 : 760 %

It was thought that the treated plots could hold more nutrients and mois-

ture than the control plot and helped the crop grew healthier

It was also thought that the gypsum provided an additional nutrient to the

crop resulting in higher yield

It was proven that the combined surface cover of straw mat, PAM and gyp-

sum could greatly decrease runoff and NPS pollution loads while increase

the lettuce yield by more than 700%

Conclusions

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IV. Conclusions

Field scale plot experiment was conducted to measure the effect of

surface mulching materials of T1, T2 and T3 on the reduction of runoff

and NPS pollution load under natural rainfall condition.

Treatment T3, a combination of straw mat, PAM and gypsum,

could reduce runoff and NPS pollution load by 68~100% and

80.9~100%, respectively, and greatly contribute to the improve-

ment of turbidity and water quality in downstream rivers and

lakes. Also T3 could help increase the yield significantly.

It was concluded that the surface mulching material combined of

rice straw mat, PAM and gypsum could be an effective BMP for the

highland agriculture in Korea

Thank You andWish You Meet in 2014 ICID Congress

in Kwangju, Korea