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Joongdae Choi, Chulhee Won and Dongkoun Yun Kangwon National University, Korea Rural Research Institute, Korea 2012. 6. 27 ICID 2012, Adelaide, Australia Effect of rice straw mat and PAM application on runoff and lettuce production from steep sloped sandy loam plots Slide 2 Contents Results and Discussion Methods and Material Conclusions Background and objectives Slide 3 Background and Objectives Slide 4 - 4 - 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 upstream regions where large scale vegetable farming is practiced on sloping fields has created serious turbidity problems and threatened 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 downstream Slide 5 I. Background The Korean Government designated the area as the prioritized soil erosion 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 - 5 - Slide 6 Examples of Structural BMPs Slide 7 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 - 7 - 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 Slide 8 I. Background Conditions 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 - 8 - Alternatives for the BMPs - No-till practices - Contour tillage - Residue cover - Application of PAM and gypsum - Adoption of furrow dam - Combination of the above Slide 9 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 - 9 - -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 Slide 10 Experiment 1 - Mulching size - Control, straw mat 300, 600, and 900 g/m 2 - 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 gypsum - 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 - 10 - I. Background Indoor Rainfall Simulation System Slide 11 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. Reduction 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 (%) - 11 - Slide 12 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 runoff SP=mat+PAM, SPS=mat+PAM+sawdust, SPR=mat+PAM+chaff - 12 - Results Effect of Mulching (Exp. 2) on Runoff Reduction (%) Slide 13 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 (%) - 13 - Results Effect of Mulching (Exp. 3) on Runoff Reduction (%) Slide 14 Results Laboratory Rainfall Simulation Studies -The experiments clearly showed that the mulching materials composed of rice straw mat, PAM, gypsum, sawdust, and rice chaff could significantly reduce runoff and sediment discharges. -It was also realized that although the addition of sawdust and chaff were effective in further reducing runoff and soil erosion, it was not practically viable. -And, field scale experiments to measure the effect of the mulching materials were required. Slide 15 Reduce the runoff Manage the muddy runoff Reduce NPS Pollution Objective Experimentally measure the effect of surface mulching materials (straw mat, PAM, Gypsum) on the reduction of runoff and NPS pollution from steep sloped experimental plots that are similar to highland agricultural fields - 15 - Slide 16 Methods and Material Slide 17 II. Methods and Materials The size of a plot : 5 30 m 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 Gypsum -PAM : 5kg/ha -Gypsum : 1,000kg/ha T3 Combination of mat, PAM and gypsum(T1 + T2) T1 Woven rice straw mat -567 kg/ha - 17 - Slide 18 - 18 - II. Methods and Materials Rice straw mat PAM and characteristics FormColorOdor Water solubility Specific gravity pH (0.5% solution) PAM Granular powder White Little or no Soluble0.75 6969 Gypsum Slide 19 II. Methods and Material - 19 - C T1 T2T3 Slide 20 Results and Discussion Slide 21 - 21 - 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 Slide 22 - 22 - III. Results and Discussion NPS pollution load and reduction ratio of the experiment DateTreatment NPS pollution load (kg)D (%) BODSSCOD Cr T-NT-PBODSSCOD Cr T-NT-P 6/23~27 C0.00170.76820.01910.01970.0019----- T10.00070.22480.010.01160.001258.870.747.641.136.8 T20.00060.13280.00720.00910.001164.782.762.353.842.1 T300000100 6/29~30 C0.00361.87990.04530.01990.0027----- T10.0020.18340.02080.01730.000844.490.254.113.170.4 T20.00320.58350.01990.01470.001411.169.056.126.148.1 T30.00060.00970.00510.00380.000283.399.588.780.992.6 7/3~4 C0.00311.68280.03730.04080.0024----- T10.00130.14280.01370.02030.000858.191.563.350.266.7 T20.00210.56920.01780.02680.00232.366.252.334.316.7 T30.00030.0110.00310.00350.000290.399.391.791.491.7 D : Reduction rate compared to control (C) Slide 23 - 23 - III. Results and Discussion Treatment effect of T1 and T2 on the reduction of NPS pollution load was acceptable 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 Slide 24 - 24 - 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 moisture 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 gypsum could greatly decrease runoff and NPS pollution loads while increase the lettuce yield by more than 700% Slide 25 Conclusions Slide 26 - 26 - 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 improvement 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 Slide 27 Thank You and Wish You Meet in 2014 ICID Congress in Kwangju, Korea