poster - International Conference of Agricultural Engineering
poster - International Conference of Agricultural Engineering poster - International Conference of Agricultural Engineering
the effect of rice straw mulch and rice straw mat mulch on the reduction of runoff and NPS pollution discharges from field scale runoff plots under natural rainfall conditions. 2. Methods Six runoff plots of 5x22 m in size were prepared in an existing sandy loam field of about 3% slope. A flume, water level meter and water sampler was installed at the lower bottom of each plot to measure runoff and collect water samples during rainfall-runoff events. Three treatments of control, rice straw mulch and rice straw mat mulch were applied right after plowing and growth bed preparation. Each treatment was duplicated. The size of rice straw and rice straw mat that was applied to the runoff plot was 3,409 kg/ha and 3,136 kg/ha, respectively. And the resulting residue cover rate of the soil surface was 64.7% and 74.7%, respectively. Spring radish and fall Chinese cabbage were cultivated and runoff and selected NPS pollution was measured under sixteen natural rainfall-runoff condition in 2011 growing season. Sixteen rainfall events were monitored with respect to runoff and concentration of selected NPS pollutants. Collected water samples were analyzed with respect to SS, TN and TP concentration by the relevant standards. And the effect of the sresidue mulch on the reduction of runoff and NPS pollution load was analyzed. 3. Results and Discussion 3.1. Rainfall characteristics Thirty year (1981~2010) average annual rainfall of the study area was 1,298.7 mm which was a little smaller than the national average of 1,307.7 mm. Frequency of heavy rainfall of 100 mm/day or higher was 1.5 times per year. Total rainfall amount of the heavy rainfall took about 17% of the total rainfall. Annual rainfall of the study area in 2010 and 2011 was 1,476.4 mm and 2,029.1 mm, respectively, which was greater than average. In 2011, rainfall frequency of 50 mm/day and 100 mm/day or higher occurred 10 and 3 times, respectively. Rainfall in 2011 was exceptionally higher than other years. It might mean that runoff and NPS pollution discharge could be larger in 2011 than other years because of the large annual rainfall. 3.2. Runoff rate The size of rainfall events during the study ranged from 12.8 mm to 538.2 mm. Runoff during the events was 0.02-39.6 m 3 from control, 0-37.4 m 3 from straw mulch, and 0-26.6 m 3 from straw mat mulch plots. Runoff rate of the 16 runoff events ranged between 0.01-0.67 (control), 0-0.63 (straw mulch), and 0-0.45 (straw mat mulch). Annual average runoff rate from control, straw mulch and straw mat mulch was 0.409, 0.299, and 0.184, respectively. These results were smaller than the results of Shin et al. (2011) who performed similar experiment with straw mat and wood shavings. It was thought that the large rainfall in 2011 increased the runoff rate in general. Reduction of runoff by straw and straw mat mulch ranged 5.4-99.7% (annual average 26.9%) and 32.9-100% (annual average 55.1%), respectively, compared to that of control plots. The annual average reduction of runoff was somewhat less than expected because of large and heavy rainfall in 2011. However, it was thought that the straw mulch effectively covered the soil surface, prevented the soil from clogging, and helped keep infiltration high, compared to control plots. Residue cover rate of straw mulch was lower than that of straw mat because the straws at the top of the ridge moved down to furrow during the growing season. Because of this, runoff reduction was larger in the straw mat mulch plots than in the straw mulch plots. The same trend also observed in NPS pollution reduction. 3.3. NPS pollution Average EMC (event mean concentration) of SS, TN and TP from control plots was 490.7 mg/L, 16.2 mg/L, and 1.4 mg/L, respectively. Average EMC from straw mulch was 289.9
mg/L, 14.6 mg/L, and 1.2 mg/L, respectively. And the EMC from straw mat mulch was 140.0 mg/L, 12.1 mg/L, and 1.2 mg/L, respectively. Average EMCs from mulched plots seemed lower than those from control plots. However, the EMCs were not significantly different at the level of 5%. NPS pollution load was computed by multiplying the EMC and runoff volume. Annual SS, TN and TP loads from control plots were 1,463.3 kg/ha, 75.1 kg/ha, and 10.4 kg/ha, respectively. Annual SS, TN and TP loads from straw mulch plots were 702.5 kg/ha, 53.7 kg/ha, and 6.7 kg/ha, respectively. And annual SS, TN and TP loads from straw mat mulch plots were 295.3 kg/ha, 23.8 kg/ha, and 4.8 kg/ha, respectively. Reduction of SS, TN and TP loads from straw mulch plots was 52.0%, 28.5%, and 35.2%, respectively, compared to those of control plots. And reduction of SS, TN and TP loads from straw mat mulch plots was 79.8%, 68.3%, and 53.3%, respectively. It was concluded that the effect of straw mulch and straw mat mulch could help reduce muddy runoff and improve water quality of receiving waters downstream even under a heavy rainfall condition in 2011. It was thought that if the rainfall in 2011 was similar to the average annual rainfall, the NPS load reduction would be much higher than those in 2011. 3.4. Productivity Leaf length, number and weight, and root stock and weight were measured at radish harvest and yield was measured. Radish yield from control, straw mulch, and straw mat mulch plots was 2,227 kg/10a, 3,050 kg/10a, and 3,126 kg/10a, respectively. It means that straw mulch and straw mat mulch increased the radish productivity 37% and 40%, respectively. For fall cabbage cultivation, cabbage yield from control, straw mulch, and straw mat mulch plots was 12,123 kg/10a, 12,927 kg/10a, 13,849 kg/10a, respectively. Productivity increase of cabbage by straw and straw mulch was 6.6% and 14.2%, respectively. The weather condition of the study site was not favourable for vegetable cultivation because of large rainfall and resulting lack of sunshine duration. And the radish and cabbage yield were less than the national average. However, it could be concluded that straw and straw mat mulch could increase yield even under unfavourable weather condition and reduce NPS pollution discharges significantly. One of very important issues in Koran rural communities is aging. Farming practices are mostly carried out by aged farmers and farm machineries. For those aged farmers, small productivity increase by the residue mulch might not be the cause to adopt the practice. Adoption and practice of crop residue mulch should be approached from the standpoint of environmental protection. And it is seriously considered that government incentives as a subsidy to improve water quality might be endowed farmers who adopt the practice. 4. Conclusions The effect of straw mulch and straw mat mulch was investigated under natural rainfall condition in 2011. Sixteen rainfall-runoff events ranging from 12.8 mm to 538.2 mm were monitored. Rainfall in 2011 was 2,029.1 mm that was much larger than the average and the weather was not favourable to vegetable cultivation. Annual reduction of runoff by straw and straw mat mulch was 26.9% and 55.1%, respectively. Average EMCs from mulched plots seemed lower than those from control plots but they were not significantly different at the level of 5%. Reduction of SS, TN and TP from straw mulch plots was 52.0%, 28.5%, and 35.2%, respectively. And reduction of SS, TN and TP from straw mat mulch plots was 79.8%, 68.3%, and 53.3%, respectively, compared to those of control plots. Yield of radish and cabbage increased with the straw mulch. Radish yield from straw mulch and straw mat mulch increased 37% and 40%, respectively. Increase of cabbage yield was 6.6% and 14.2%, respectively. It was concluded that straw and straw mat mulch could increase vegetable yield and reduce NPS pollution discharges significantly. It was also recommended that government incentives for farmers to adopt straw mulch practices be seriously considered.
- Page 175 and 176: Q P Ia 2 P Ia S for P≥Ia Q 0
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mg/L, 14.6 mg/L, and 1.2 mg/L, respectively. And the EMC from straw mat mulch was 140.0<br />
mg/L, 12.1 mg/L, and 1.2 mg/L, respectively. Average EMCs from mulched plots seemed<br />
lower than those from control plots. However, the EMCs were not significantly different at the<br />
level <strong>of</strong> 5%. NPS pollution load was computed by multiplying the EMC and run<strong>of</strong>f volume.<br />
Annual SS, TN and TP loads from control plots were 1,463.3 kg/ha, 75.1 kg/ha, and 10.4<br />
kg/ha, respectively. Annual SS, TN and TP loads from straw mulch plots were 702.5 kg/ha,<br />
53.7 kg/ha, and 6.7 kg/ha, respectively. And annual SS, TN and TP loads from straw mat<br />
mulch plots were 295.3 kg/ha, 23.8 kg/ha, and 4.8 kg/ha, respectively. Reduction <strong>of</strong> SS, TN<br />
and TP loads from straw mulch plots was 52.0%, 28.5%, and 35.2%, respectively, compared<br />
to those <strong>of</strong> control plots. And reduction <strong>of</strong> SS, TN and TP loads from straw mat mulch plots<br />
was 79.8%, 68.3%, and 53.3%, respectively. It was concluded that the effect <strong>of</strong> straw mulch<br />
and straw mat mulch could help reduce muddy run<strong>of</strong>f and improve water quality <strong>of</strong> receiving<br />
waters downstream even under a heavy rainfall condition in 2011. It was thought that if the<br />
rainfall in 2011 was similar to the average annual rainfall, the NPS load reduction would be<br />
much higher than those in 2011.<br />
3.4. Productivity<br />
Leaf length, number and weight, and root stock and weight were measured at radish harvest<br />
and yield was measured. Radish yield from control, straw mulch, and straw mat mulch plots<br />
was 2,227 kg/10a, 3,050 kg/10a, and 3,126 kg/10a, respectively. It means that straw mulch<br />
and straw mat mulch increased the radish productivity 37% and 40%, respectively. For fall<br />
cabbage cultivation, cabbage yield from control, straw mulch, and straw mat mulch plots was<br />
12,123 kg/10a, 12,927 kg/10a, 13,849 kg/10a, respectively. Productivity increase <strong>of</strong> cabbage<br />
by straw and straw mulch was 6.6% and 14.2%, respectively. The weather condition <strong>of</strong> the<br />
study site was not favourable for vegetable cultivation because <strong>of</strong> large rainfall and resulting<br />
lack <strong>of</strong> sunshine duration. And the radish and cabbage yield were less than the national<br />
average. However, it could be concluded that straw and straw mat mulch could increase<br />
yield even under unfavourable weather condition and reduce NPS pollution discharges<br />
significantly.<br />
One <strong>of</strong> very important issues in Koran rural communities is aging. Farming practices are<br />
mostly carried out by aged farmers and farm machineries. For those aged farmers, small<br />
productivity increase by the residue mulch might not be the cause to adopt the practice.<br />
Adoption and practice <strong>of</strong> crop residue mulch should be approached from the standpoint <strong>of</strong><br />
environmental protection. And it is seriously considered that government incentives as a<br />
subsidy to improve water quality might be endowed farmers who adopt the practice.<br />
4. Conclusions<br />
The effect <strong>of</strong> straw mulch and straw mat mulch was investigated under natural rainfall<br />
condition in 2011. Sixteen rainfall-run<strong>of</strong>f events ranging from 12.8 mm to 538.2 mm were<br />
monitored. Rainfall in 2011 was 2,029.1 mm that was much larger than the average and the<br />
weather was not favourable to vegetable cultivation. Annual reduction <strong>of</strong> run<strong>of</strong>f by straw and<br />
straw mat mulch was 26.9% and 55.1%, respectively. Average EMCs from mulched plots<br />
seemed lower than those from control plots but they were not significantly different at the<br />
level <strong>of</strong> 5%. Reduction <strong>of</strong> SS, TN and TP from straw mulch plots was 52.0%, 28.5%, and<br />
35.2%, respectively. And reduction <strong>of</strong> SS, TN and TP from straw mat mulch plots was 79.8%,<br />
68.3%, and 53.3%, respectively, compared to those <strong>of</strong> control plots. Yield <strong>of</strong> radish and<br />
cabbage increased with the straw mulch. Radish yield from straw mulch and straw mat mulch<br />
increased 37% and 40%, respectively. Increase <strong>of</strong> cabbage yield was 6.6% and 14.2%,<br />
respectively. It was concluded that straw and straw mat mulch could increase vegetable yield<br />
and reduce NPS pollution discharges significantly. It was also recommended that<br />
government incentives for farmers to adopt straw mulch practices be seriously considered.
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