Urbanization affects water and nitrogen use in the food chain in China
European Journal of Cardiovascular Prevention & Rehabilitation, 2012
Abstract: Urbanization and agriculture are highly coupled. However, the impacts of urbanization(e... more Abstract: Urbanization and agriculture are highly coupled. However, the impacts of urbanization(e.g. transformation in urban and rural population and change in diet) on water and nitrogen (N) use remain poorly understood. The objectives of this study are to quantify water flows in the food chain of China, to analyze the complex relationship between urbanization and water and N use efficiency,
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stages of maize growth, and more importantly, it reduced diurnal temperature variation. MS also increased in soil water storage by 10.1%, leading to the highest water use efficiency (WUE = 30.9 kg ha−1 mm−1) over CK on 3 year average. MS significantly increased maize yield and net income of farmers by up to 20%, compared to CK. In conclusion, optimisation of soil mulching strategies significantly enhanced crop yield and water productivity in dryland agriculture in China. Our study provides important guidance for exploring better soil management practice for dryland agriculture in the other regions of the world.
Here, we present the results of an integrated assessment of the N and P use efficiencies (NUE and PUE) and N and P losses in the chain of crop and animal production, food processing and retail, and food consumption at regional scale in 1980 and 2005, using a uniform approach and databases. Our results show that the N and P costs of food production–consumption almost doubled between 1980 and 2005, but with large regional variation. The NUE and PUE of crop production decreased dramatically, while NUE and PUE in animal production increased. Interestingly, NUE and PUE of the food processing sector decreased from about 75% to 50%. Intake of N and P per capita increased, but again with large regional variation. Losses of N and P from agriculture to atmosphere and water bodies increased in most regions, especially in the east and south of the country. Highest losses were estimated for the Beijing and Tianjin metropolitan regions (North China), Pearl River Delta (South China) and Yangzi River Delta (East China).
In conclusion, the changes and regional variations in NUE and PUE in the food chain of China are large and complex. Changes occurred in the whole crop and animal production, food processing and consumption chain, and were largest in the most populous areas between 1980 and 2005.
Sufficient soil phosphorus (P) is important for achieving optimal crop production, but excessive soil P levels may create a risk of P losses and associated eutrophication of surface waters. The aim of this study was to determine critical soil P levels for achieving optimal crop yields and minimal P losses in common soil types and dominant cropping systems in China.
Methods
Four long-term experiment sites were selected in China. The critical level of soil Olsen-P for crop yield was determined using the linear-plateau model. The relationships between the soil total P, Olsen-P and CaCl2-P were evaluated using two-segment linear model to determine the soil P fertility rate and leaching change-point.
Results
The critical levels of soil Olsen-P for optimal crop yield ranged from 10.9 mg kg−1 to 21.4 mg kg−1, above which crop yield response less to the increasing of soil Olsen-P. The P leaching change-points of Olsen-P ranged from 39.9 mg kg−1 to 90.2 mg kg−1, above which soil CaCl2-P greatly increasing with increasing soil Olsen-P. Similar change-point was found between soil total P and Olsen-P. Overall, the change-point ranged from 4.6 mg kg−1 to 71.8 mg kg−1 among all the four sites. These change-points were highly affected by crop specie, soil type, pH and soil organic matter content.
Conclusions
The three response curves could be used to access the soil Olsen-P status for crop yield, soil P fertility rate and soil P leaching risk for a sustainable soil P management in field.
The simulations showed that orange yields were strongly influenced by N input and N split applications, but not so much by irrigation. Increasing water and N input led to increased N losses (via leaching and denitrification), and there were significant positive interactions between water and N input with respect to N losses. On average, low N input (100 kg ha-1) led to relatively low N losses (16 kg ha-1) but resulted in low yield (33 ton ha-1, 25% yield reduction). High N input (300 kg ha-1) produced a high yield (43 ton ha-1) but led to large N losses (104 kg ha-1). Optimal N input (200 kg ha-1) significantly reduced N losses (45 kg ha 1) without yield reduction. Importantly, with optimal N input, improving N split applications significantly increased yield by 13% and reduced N losses by 40%, compared to sub-optimal N splits.
Significant interactions between water inputs, N inputs and N split applications in yield and N losses indicate that the optimization of fertigation strategies must consider these three key variables simultaneously. Our results clearly show that over-optimal water and N inputs lead to large water and N losses. Reduced irrigation (80% of water demand) and N input equal to N demand (200 kg ha-1) can significantly reduce N losses without yield reduction. The N split applications should be adjusted to the N demand of the crop during the growing season. Our study focused on a Mediterranean climate, but the methodology and results can be applied to other situations in the world.
stages of maize growth, and more importantly, it reduced diurnal temperature variation. MS also increased in soil water storage by 10.1%, leading to the highest water use efficiency (WUE = 30.9 kg ha−1 mm−1) over CK on 3 year average. MS significantly increased maize yield and net income of farmers by up to 20%, compared to CK. In conclusion, optimisation of soil mulching strategies significantly enhanced crop yield and water productivity in dryland agriculture in China. Our study provides important guidance for exploring better soil management practice for dryland agriculture in the other regions of the world.
Here, we present the results of an integrated assessment of the N and P use efficiencies (NUE and PUE) and N and P losses in the chain of crop and animal production, food processing and retail, and food consumption at regional scale in 1980 and 2005, using a uniform approach and databases. Our results show that the N and P costs of food production–consumption almost doubled between 1980 and 2005, but with large regional variation. The NUE and PUE of crop production decreased dramatically, while NUE and PUE in animal production increased. Interestingly, NUE and PUE of the food processing sector decreased from about 75% to 50%. Intake of N and P per capita increased, but again with large regional variation. Losses of N and P from agriculture to atmosphere and water bodies increased in most regions, especially in the east and south of the country. Highest losses were estimated for the Beijing and Tianjin metropolitan regions (North China), Pearl River Delta (South China) and Yangzi River Delta (East China).
In conclusion, the changes and regional variations in NUE and PUE in the food chain of China are large and complex. Changes occurred in the whole crop and animal production, food processing and consumption chain, and were largest in the most populous areas between 1980 and 2005.
Sufficient soil phosphorus (P) is important for achieving optimal crop production, but excessive soil P levels may create a risk of P losses and associated eutrophication of surface waters. The aim of this study was to determine critical soil P levels for achieving optimal crop yields and minimal P losses in common soil types and dominant cropping systems in China.
Methods
Four long-term experiment sites were selected in China. The critical level of soil Olsen-P for crop yield was determined using the linear-plateau model. The relationships between the soil total P, Olsen-P and CaCl2-P were evaluated using two-segment linear model to determine the soil P fertility rate and leaching change-point.
Results
The critical levels of soil Olsen-P for optimal crop yield ranged from 10.9 mg kg−1 to 21.4 mg kg−1, above which crop yield response less to the increasing of soil Olsen-P. The P leaching change-points of Olsen-P ranged from 39.9 mg kg−1 to 90.2 mg kg−1, above which soil CaCl2-P greatly increasing with increasing soil Olsen-P. Similar change-point was found between soil total P and Olsen-P. Overall, the change-point ranged from 4.6 mg kg−1 to 71.8 mg kg−1 among all the four sites. These change-points were highly affected by crop specie, soil type, pH and soil organic matter content.
Conclusions
The three response curves could be used to access the soil Olsen-P status for crop yield, soil P fertility rate and soil P leaching risk for a sustainable soil P management in field.
The simulations showed that orange yields were strongly influenced by N input and N split applications, but not so much by irrigation. Increasing water and N input led to increased N losses (via leaching and denitrification), and there were significant positive interactions between water and N input with respect to N losses. On average, low N input (100 kg ha-1) led to relatively low N losses (16 kg ha-1) but resulted in low yield (33 ton ha-1, 25% yield reduction). High N input (300 kg ha-1) produced a high yield (43 ton ha-1) but led to large N losses (104 kg ha-1). Optimal N input (200 kg ha-1) significantly reduced N losses (45 kg ha 1) without yield reduction. Importantly, with optimal N input, improving N split applications significantly increased yield by 13% and reduced N losses by 40%, compared to sub-optimal N splits.
Significant interactions between water inputs, N inputs and N split applications in yield and N losses indicate that the optimization of fertigation strategies must consider these three key variables simultaneously. Our results clearly show that over-optimal water and N inputs lead to large water and N losses. Reduced irrigation (80% of water demand) and N input equal to N demand (200 kg ha-1) can significantly reduce N losses without yield reduction. The N split applications should be adjusted to the N demand of the crop during the growing season. Our study focused on a Mediterranean climate, but the methodology and results can be applied to other situations in the world.