what can we learn from long-term paddy and vegetable field experiments for better nutrients management and

less environmental impact in Taihu Lake region?

Institute of Soil Science Chinese Academy of Sciences

Nanjing, China

Ju MIN, Jun QIAO, Tingmei YAN, Xu ZHAO, Weiming SHI

中英养分管理和水资源保护学术研讨会China-UK nutrient management and water resource protection workshop

N Runoff

Leaching

To obtain high yield, large amount of fertilizer N is applied in China.

Consequently, considerable amount of N enters the environment through volatilization, runoff and leaching. This threat to environment is more serious in the Taihu Lake region.

volatilization

A typical rice-wheat rotaion field in Yixing, Jiangsu Province, the experiment starts 2008 (6y, 12 crop season) (another from 2003)

Experimental site：

Taihu Lake

TO evaluate fertilizer N impact on environment and balance of high yield and environmental cost, two

long-term field experiments were conducted

A typical greenhouse vegetable production farm in Yixing, Jiangsu Province, the experiment starts from 2005 (8y, 24 crop seasons)

Cropping system: Double crops: rice-wheat (from 2008 to 2013) rice-alfalfa (from 2010 to 2013)

Fertilizer treatments：

1. Long-term paddy field experiments

N rates (kg N/ha)

Rice-wheat rotation

100%N 90%N 80%N 70%N 50%N 30%N CK

Rice 270 243 216 189 135 81 0

Wheat 240 216 192 168 120 72 0

Rice-alfalfa rotation

100%N 55%N 44%N 33%N 22%N 11%N CK

Rice 270 150 120 90 60 30 0

Alfalfa

(Provided to the soil)

90.5±8.3 92.1±8.4 86.7±12.5 88.3±7.3 87.8±7.3 84.6±7.3 79.7±7.5

All treatments received 81 kg K/ha and 81 kg P/ha in rice season and 96 kg K/ha and 96 kg P/ha in wheat season as basal fertilizer.

Cropping system: Triple crops: Tomato-Cucumber-Celery (from 2006 to 2009) Tomato- Lettuce -Celery (from 2010 to now)

Fertilizer treatments：N rates (kg N/ha)

Treatment Tomato Cucumber / Lettuce Celery

100%N (traditional synthetic N rate)

300 270 300

80%N 240 216 240

60%N 180 163 180

40%N 120 108 120

CK(no synthetic N) 0 0 0

All treatments received 78 kg N /ha from animal manure in addition to 150 kg K2O/ha and 120 kg P2O5 /ha as basal fertilizer each season.

2. Long-term greenhouse vegetable field experiments

Rice Wheat

N fate in rice-wheat rotation (average of 6 years)

The trends of rice yield and the yields after six years

50% N

Control measures: Optimizing N input

The N runoff in different N rates of rice season under rice-wheat rotation

Wheat-rice

rotation　Run off in rice season (kg N/ha)

2008 2009 2010 2011 2012 Average

CK 7.34±0.92 12.37±3.48 4.59±0.83 2.2±0.4 6.6±1.7 6.6

30%N N/A N/A N/A 4.7±0.7 9.5±2.2 7.2

50%N 8.8±1.5 26.6±3.0 12.1±2.5 8.5±0.9 10.4±2.1 13.3

70%N 10.1±2.0 35.8±7.8 16.3±2.6 9.6±0.8 13.9±2.4 17.2

80%N 12.2±1.8 43.7±6.9 18.8±2.7 10.1±2.9 15.1±2.6 20.0

90%N 13.0±2.1 37.7±3.2 20.7±2.8 11.6±4.2 15.1±2.3 19.7

100%N 15.2±2.5 57.5±5.2 22.3±3.2 13.2±4.8 19.4±3.6 25.6

By decreasing traditional rate of synthetic N fertilizer by 30% run off was reduced by 33% without any yield loss in rice season under rice-wheat rotation

Alfalfa-Rice rotation

Rice yield (kg/ha)

2010 2011 2012 2013 Average

CK 4789±179 6275±234 5414±90 5594±371 5518

11%N 5034±90 6306±89 5766±261 6262±115 5842

22%N 5478±334 6901±374 6572±1074 6670±129 6407

33%N 5794±357 7088±482 6887±641 7201±167 6742

44%N 5942±80 7412±200 7411±641 7399±160 7041

55%N 5879±174 7296±184 7725±199 7264±656 7041

100%N 6735±208 7084±665 8778±558 7317±477 7479

Control measures ： Optimizing N input and Alfalfa-Rice rotation

When alfalfa incorporated into rice cropping system, decreasing traditional rate of synthetic N fertilizer by 56% ( 44%N ) will not lead any yield loss in rice season.

Alfalfa-Rice rotation

Annual runoff (kg N/ha)

2010 2011 2012 Average

CK 5.96±1.14 1.83±0.37 6.02±0.88 4.60

11%N 6.99±1.44 1.90±0.18 6.18±1.02 5.02

22%N 9.54±1.22 2.27±0.12 6.50±0.81 6.10

33%N 11.26±0.63 3.67±1.20 6.75±0.97 7.23

44%N 16.02±1.43 6.08±1.35 7.12±1.15 9.74

55%N 18.50±2.26 6.99±2.06 7.96±0.92 11.15

100%N 29.88±3.28 20.78±4.26 31.41±6.52 27.36

Compared to local farmers’ normal N usage, reducing fertilizer N input by 56% under Alfalfa-Rice rotation reduced total N runoff by 64%.

The annual runoff in different N rates under Alfalfa-Rice rotation

N fate under the greenhouse vegetable cropping system in

Taihu Lake region.

(Min, et al. Pedosphere, 2011; Min, et al. Soil Use and Management, 2012)

Control measures: Optimizing N input

The optical N input is 930 kg N/ha (manure + synthetic N: 234+696)

（ kg/ha）

By decreasing traditional rate of synthetic N fertilizer by 40% leaching loss was reduced by 39% without any yield loss in intensive greenhouse vegetable production systems. (Min, et al. Agricultural Water Management, 2011)

Optimizing nitrogen input to reduce nitrate leaching loss in greenhouse vegetable production

RNL: Reduced N leaching

Treatment 2007 2008 2009 2010 2011 2012 6 Y average

R N L Yield R N L Yield R N L Yield R N L Yield R N L Yield R N L Yield R N L Yield

N870（ farme

r）-- 210 -- 183 -- 149 -- 165 -- 141 -- 126 -- 162

N696（ -20%） 38 197 35 195 19 156 31 174 59 159 46 170 38 175

N522（ -40%） 68 202 59 179 61 156 85 165 148 162 94 158 86 170

N348（ -60%） 111 159 83 130 85 128 110 133 178 125 204 141 129 136

The effect of catch crop on the amount of total N leached (kg/ ha) and the relative total N captured by the catch crop in 2008 and 2009

(Min, et al. Nutr Cycl Agroecosyst, 2011)

Compared to local farmers’ normal N usage, reducing fertilizer N input by 20 and 40% with a sweet corn catch crop reduced total N leaching by 50 and 73%, respectively.

Control measures: Catch crop

Conclusions1. In rice cropping system:

Optimal N input is 190 kg N/ha in rice season under rice-wheat rotation.

3% and 12% N were lost by runoff and leaching under farmer’s N input level .

By decreasing traditional rate of synthetic N fertilizer by 30% run off was reduced by 33% without any yield loss in rice season under rice-wheat rotation.

By decreasing traditional rate of synthetic N fertilizer by 56%( 44%N ) under Alfalfa-Rice rotation reduced total N runoff by 64% and also maintain the rice yields.

Optimal N input is 930 kg N/ha for vegetables.

3% and 20% N were lost by runoff and leaching under farmer’s N input level .

By decreasing traditional rate of synthetic N fertilizer by 40%, leaching loss was reduced by 39% without any yield loss;

Compared to local farmers’ normal N usage, reducing fertilizer N input by 20 and 40% with a sweet corn catch crop, this reduction could reach to 50 and 73%, respectively.

2. In greenhouse vegetable cropping system:

研究进展

Long-term rice-vegetable rotation experiments was started in 2013 in this region. Cropping system: Rice-vegetable rotation: Cabbage-rice-brassica chinensis CK: Cabbage-kidney bean-radish-brassica chinensis

Fertilizer treatments ： 1) 100%N (traditional synthetic N rate) 2) 70% N 3) 40%N 4) CK (no synthetic N)

The next step---

Taihu Lake

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