• Authors:
    • Hoogenboom, G.
    • Yang, X. M.
    • Dou, S.
    • Yang, J. Y.
    • Yang, J. M.
  • Source: NUTRIENT CYCLING IN AGROECOSYSTEMS
  • Volume: 95
  • Issue: 3
  • Year: 2013
  • Summary: Simulation models are being regarded as an important tool to simulate crop growth, soil nutrient dynamics and soil carbon sequestration and fast use of the embedded knowledge of crop-soil processes. The Decision Support Systems for Agrotechnology Transfer (DSSAT) model was used to simulate long-term continuous maize growth from 1990 to 2007 in Gongzhuling, Northeast China. Three levels of N treatments were simulated, including: (1) no N (N0), (2) 165 kg N ha(-1) from synthetic fertilizer (N165) and (3) 50 kg N ha(-1) from synthetic fertilizer plus 115 kg N ha(-1) from farmyard manure (N165M). Both measured and simulated results showed that the maize yield was significantly lower in the N0 treatment. The measured maize yield was higher in N165M than N165 treatments after 2003. The maize yield was also affected by the weather, especially during drought years. The simulated soil organic C (SOC) content was in good agreement with the measured data in the 0-30 cm depth for all treatments. The SOC density in the 0-30 cm depth decreased by 4,393 kg C ha(-1) (18 %) in the N0 treatment and 4,186 kg C ha(-1) (17 %) in the N165 treatment, while it increased by 13,628 kg C ha(-1) (54 %) in the N165M treatment during 1990-2007, indicating that the combination of inorganic fertilizer and organic manure improved soil quality after 27 years of organic amendment from 1980. Soil mineral N levels were significantly higher in the N165 treatment just before planting (averaged 289 kg N ha(-1)), associated with more soil N leaching during the growing seasons (24-155 kg N ha(-1)) in some wet years, while soil mineral N levels were much lower in both the N0 (averaged 52 kg N ha(-1)) and N165M treatments (averaged 54 kg N ha(-1)) associated with less N leaching (< 10 kg N ha(-1)) compared with the N165 treatment. This indicated that the use of farmyard manure increased the soil organic matter and immobilized mineral N. The model results further indicated that complete crop residue removal from the field after harvest was a main reason for the decline of the SOC in the N165 treatment, suggesting that crop residue should be left on the soil to maintain the SOC balance and promote sustainable agriculture. Thus, we conclude that the DSSAT CENTURY-based module is a useful tool to simulate soil nitrogen dynamics and predict soil organic carbon sequestration in long-term field conditions.
  • Authors:
    • Zhang, W.
    • Huang, Y.
    • Yu, Y. Q.
  • Source: AGRICULTURE ECOSYSTEMS & ENVIRONMENT
  • Volume: 178
  • Year: 2013
  • Summary: The timing, magnitude, and regional distribution of soil organic carbon (SOC) changes are uncertain when factoring in climate change and agricultural management practices. The goal of this study is to analyze the implications of changes in climate and agricultural management for Chinese soil carbon sequestration over the next 40 years. We used the Agro-C model to simulate climate and agricultural management scenarios to investigate the combined impacts of climate change and management on future SOC stocks in China's croplands. The model was run for croplands on mineral soils in China, which make up a total of 130 M ha of cropland. The model used climate data (years 2011-2050) from the FGOALS and PRECIS climate models based on four Intergovernmental Panel on Climate Change (IPCC) emissions scenarios. Three equidistant agricultural management scenarios were used. S0 was a current scenario, and S2 was an optimal scenario. Under the S2 scenario, crop yields increased annually by 1%, the proportion of crop residue retained in the field reached 90% by 2050, and the area of no-tillage increased to 50% of the cultivated area by 2050. The S1 scenario applied half of the increased rates in crop yields, residue retention and no-tillage area values that were used in the S2 scenario. Across all croplands in China, the results suggest that SOC will increase under all combinations of climate and management and that the effect of climate change is much smaller than the effect of changes in agricultural management. Most croplands in China show a significant increase in SOC stocks, while very few zones (mainly in northeastern China) show a decrease. Rice paddy soils under the intensive farming management scenario show higher rates of carbon sequestration than dry-land soils. The maximum carbon sequestration potential of the croplands of China is estimated to be 2.39 Pg C under S2. Annual increases in SOC stocks could offset a maximum of 2.9% of the CO 2 emissions from fossil-fuel combustion in 2009. These results suggest that China's croplands, especially rice paddies, may play an important role in C sequestration and future climate change mitigation.
  • Authors:
    • Wang, X. Y.
    • Turner, N. C.
    • Yang, J. Y.
    • Li, M.
    • Li, X. G.
    • Li, Z. T.
    • Li, F. M.
  • Source: SOIL SCIENCE SOCIETY OF AMERICA JOURNAL
  • Volume: 77
  • Issue: 6
  • Year: 2013
  • Summary: The Loess Plateau is an area of low crop productivity and one of the most susceptible areas for soil erosion in China. This study was designed to investigate changes in soil organic carbon (SOC) of croplands in four humid to semiarid counties (Huixian, Xifeng, Linxia, and Yuzhong) of Gansu province that have experienced accelerated grain production since the early 1980s. In 1979 to 1988 and 2006 to 2007, respectively, 2036 and 15,764 topsoil (20-cm) samples were collected and analyzed for SOC concentration and density from croplands covering 12 Chinese soil groups. By comparing the SOC data from the mid-2000s and the 1980s, we found that across the four counties, topsoil (20-cm) SOC concentration and density in croplands changed significantly (P < 0.01) at a rate of 0.04 ± 0.14 g kg-1 yr-1 or 0.01 ± 0.03 kg m-2 yr-1 from 7.9 ± 3.5 g kg-1 and 1.98 ± 0.9 kg m-2 in the 1980s to 8.7 ± 2.4 g kg-1 and 2.22 ± 0.5 kg m-2 in the mid-2000s, respectively. This overall increase in topsoil (20-cm) SOC concentration by 10% or density by 12% in the mid-2000s was associated with an increase of 83% in the stubble and root inputs to the soil across the four counties. There were large differences in the change size in the cropland topsoil (20-cm) SOC concentration and density among counties. In Huixian and Xifeng, both the topsoil SOC concentration and density in the mid-2000s were significantly higher than in the 1980s (P < 0.01), whereas there were no significant changes in topsoil SOC concentration and density in either Linxia or Yuzhong. Soils with lower initial SOC tended to increase more in SOC concentration than soils with higher initial SOC. © Soil Science Society of America. All rights reserved.
  • Authors:
    • Zhao, Y. G.
    • Sun, Y. J.
    • Zhang, G. L.
    • Liu, F.
    • Li, D. C.
  • Source: SOIL SCIENCE SOCIETY OF AMERICA JOURNAL
  • Volume: 77
  • Issue: 4
  • Year: 2013
  • Summary: There is a serious lack of detailed and accurate three-dimensional soil distribution information worldwide. This study examined the effectiveness of combining radial basis function (RBF) neural networks and profile depth functions to map the three-dimensional distribution of soil organic matter (SOM) in a subtropical hilly landscape in southern Anhui Province, China. The RBF networks were used to predict the lateral distribution of SOM based on its relations with terrain attributes and land uses, while the depth functions were used to fit its vertical distribution based on sparse measurements of SOM in soil genetic horizons. Compared with power and logarithmic functions, the equal-area quadratic splines had smaller bias, higher accuracy, and more stable performance in fitting the vertical SOM distribution. The prediction accuracy of the whole three-dimensional mapping method decreased with depth within the upper 60 cm, while the best accuracy occurred below 60 cm. In the upper 30 cm, areas with high elevation tended to have high predicted SOM content and vice versa. There were local deviations from this pattern in areas where toeslopes and ravines had higher predicted SOM content than backslopes, even though the latter are at higher elevations. Multiple regressions with dummy variables showed that the influence of terrain conditions on SOM content was strong in the upper 60 cm and weak below 60 cm, while that of land use was strong in the upper 30 cm and weak below 30 cm. Both influences were the strongest in the upper 15-cm soil layer. Under the same terrain conditions, agricultural cultivation is associated with SOM accumulation in the upper 30 cm. © Soil Science Society of America.
  • Authors:
    • Zhang, F. S.
    • Yuan, L.X.
    • Yang, X. L.
    • Gao, Q.
    • Chen, Y. L.
    • Chen, F. J.
    • Chen, X. C.
    • Mi, G. H.
  • Source: Global Change Biology
  • Volume: 19
  • Issue: 3
  • Year: 2013
  • Summary: The impact of global changes on food security is of serious concern. Breeding novel crop cultivars adaptable to climate change is one potential solution, but this approach requires an understanding of complex adaptive traits for climate-change conditions. In this study, plant growth, nitrogen (N) uptake, and yield in relation to climatic resource use efficiency of nine representative maize cultivars released between 1973 and 2000 in China were investigated in a 2-year field experiment under three N applications. The Hybrid-Maize model was used to simulate maize yield potential in the period from 1973 to 2011. During the past four decades, the total thermal time (growing degree days) increased whereas the total precipitation and sunshine hours decreased. This climate change led to a reduction of maize potential yield by an average of 12.9% across different hybrids. However, the potential yield of individual hybrids increased by 118.5 kg ha -1 yr -1 with increasing year of release. From 1973 to 2000, the use efficiency of sunshine hours, thermal time, and precipitation resources increased by 37%, 40%, and 41%, respectively. The late developed hybrids showed less reduction in yield potential in current climate conditions than old cultivars, indicating some adaptation to new conditions. Since the mid-1990s, however, the yield impact of climate change exhibited little change, and even a slight worsening for new cultivars. Modern breeding increased ear fertility and grain-filling rate, and delayed leaf senescence without modification in net photosynthetic rate. The trade-off associated with delayed leaf senescence was decreased grain N concentration rather than increased plant N uptake, therefore N agronomic efficiency increased simultaneously. It is concluded that modern maize hybrids tolerate the climatic changes mainly by constitutively optimizing plant productivity. Maize breeding programs in the future should pay more attention to cope with the limiting climate factors specifically.
  • Authors:
    • Chen, X. P.
    • Zhang, F. S.
    • Li, S. Q.
    • Zhang, Q.
    • Yang, Z. P.
    • Wu, L.
    • Meng, Q. F.
    • Wang, G. L.
    • Yue, S. C.
    • Cui, Z. L.
  • Source: Global Change Biology
  • Volume: 19
  • Issue: 8
  • Year: 2013
  • Summary: Although the goal of doubling food demand while simultaneously reducing agricultural environmental damage has become widely accepted, the dominant agricultural paradigm still considers high yields and reduced greenhouse gas (GHG) intensity to be in conflict with one another. Here, we achieved an increase in maize yield of 70% in on-farm experiments by closing the yield gap and evaluated the trade-off between grain yield, nitrogen (N) fertilizer use, and GHG emissions. Based on two groups of N application experiments in six locations for 16 on-farm site-years, an integrated soil-crop system (HY) approach achieved 93% of the yield potential and averaged 14.8 Mg ha -1 maize grain yield at 15.5% moisture. This is 70% higher than current crop (CC) management. More importantly, the optimal N rate for the HY system was 250 kg N ha -1, which is only 38% more N fertilizer input than that applied in the CC system. Both the N 2O emission intensity and GHG intensity increased exponentially as the N application rate increased, and the response curve for the CC system was always higher than that for the HY system. Although the N application rate increased by 38%, N 2O emission intensity and the GHG intensity of the HY system were reduced by 12% and 19%, respectively. These on-farm observations indicate that closing the yield gap alongside efficient N management should therefore be prominent among a portfolio of strategies to meet food demand while reducing GHG intensity at the same time.
  • Authors:
    • Zhou, D.
    • Wang, J.
    • Chen, Z.. L.
    • Bi, C. J.
  • Source: Pedosphere
  • Volume: 23
  • Issue: 2
  • Year: 2013
  • Summary: Soil health assessment is an important step toward understanding the potential effects of agricultural practices on crop yield, quality and human health. The objectives of this study were to select a minimum data set for soil health evaluation from the physical, chemical and biological properties and environmental pollution characteristics of agricultural soil and to develop a soil health diagnosis model for determining the soil health status under different planting patterns and soil types in Chongming Island of Shanghai, China. The results showed that the majority of the farmland soils in Chongming Island were in poor soil health condition, accounting for 48.9% of the survey samples, followed by the medium healthy soil, accounting for 32.2% of the survey samples and mainly distributed in the central and mid-eastern regions of the island. The indicators of pH, total organic carbon, microbial biomass carbon and Cd exerted less influence on soil health, while the soil salinization and nitrate accumulation under a greenhouse cropping pattern and phosphate fertilizer shortage in the paddy field had limited the development of soil health. Dichlorodiphenyltrichloroethanes, hexachlorocyclohexanes and Hg contributed less to soil health index (SHI) and showed no significant difference among paddy field, greenhouse and open-air vegetable/watermelon fields. The difference of the SHI of the three soil types was significant at P = 0.05. The paddy soil had the highest SHI values, followed by the gray alluvial soil, and the coastal saline soil was in a poor soil health condition, indicating a need to plant some salt-tolerant crops to effectively improve soil quality.
  • Authors:
    • Wu, J.
    • Luo, Z. Z.
    • Wang, J.
    • Cai, L. Q.
    • Zhang, R. Z.
  • Source: Zhongguo Shengtai Nongye Xuebao / Chinese Journal of Eco-Agriculture
  • Volume: 21
  • Issue: 8
  • Year: 2013
  • Summary: This study analyzed the effects of different tillage conditions on greenhouse gas emissions of double sequence pea-wheat rotation fields during 2011. Three greenhouse gases (CO 2, N 2O and CH 4) emission were investigated under four tillage types [conventional tillage without straw mulching (T), no-tillage without straw mulching (NT), conventional tillage with straw mulching (TS) and no-tillage with straw mulching (NTS)]. The carbon dioxide analyzer and static chamber-gas chromatographic techniques were used to continuously measure and analyze the greenhouse gases fluxes. The results showed that double sequence pea-wheat rotation fields served not only as source of atmospheric CO 2, N 2O, but also as sink of atmospheric CH 4. Compared with T, NT retarded CO 2 emission. The three conservation tillage methods of NTS, NT and TS reduced N 2O emission but significantly increased CH 4 absorption. CO 2 and N 2O fluxes were significantly correlated with topsoil temperature ( R2=0.92** and 0.89**), soil temperature at the 5 cm soil depth ( R2=0.95** and 0.91**) and soil temperature at the 10 cm soil depth ( R2=0.77* and 0.62*). CH 4 fluxes were uncorrected with soil temperature at different soil depths. The correlation coefficients between CO 2 and soil water content, and CH 4 and soil water content at 0-5 cm soil layer were 0.69* and 0.72*, respectively. The correlation coefficient between CO 2 and soil water content at the 5-10 cm soil layer was 0.77* and that between CH 4, and soil water content at the 5-10 cm soil layer was 0.64*. CO 2, CH 4, fluxes were positively correlated with soil water content at the 10-30 cm soil layer. N 2O fluxes showed negative correlations with soil water content at different soil layers. The calculated global warming potential of the three greenhouse gases under the different tillage conditions showed that NT limited greenhouse gas flux, thereby reducing greenhouse effect.
  • Authors:
    • Zhang, Y.
    • Wu, L.
    • Wang, H.
    • Liu, L.
    • Huang, L.
    • Niu, Y.
    • Chai, R.
  • Source: Nutrient Cycling in Agroecosystems
  • Volume: 96
  • Issue: 1
  • Year: 2013
  • Summary: Proper management of synthetic nitrogen (N) fertilizer can reduce direct N2O emission from soil and indirect CO2 emission from production and transportation of synthetic N. In the late 1990s, the average application rates of synthetic N were 212, 207 and 207 kg ha(-1), respectively, for rice, wheat, and maize in China's croplands. But research suggests that the optimal synthetic N application rates for the main grain crops in China should be in the range of 110-150 kg ha(-1). Excessive application of synthetic N has undoubtedly resulted in massive emission of greenhouse gases. Therefore, optimizing N application rates for grain crops in China has a great potential for mitigating the emission of greenhouse gases. Nevertheless, this mitigation potential (MP) has not yet been well quantified. This study aimed at estimating the MP of N2O and CO2 emissions associated with synthetic N production and transportation in China based on the provincial level statistical data. Our research indicates that the total consumption of synthetic N on grain crops in China can be reduced by 5.0-8.4 Tg yr(-1) (28-47 % of the total consumption) if the synthetic N application rate is controlled at 110-150 kg ha(-1). The estimated total MP of greenhouse gases, including direct N2O emission from croplands and indirect CO2 emission from production and transportation of synthetic N, ranges from 41.7 to 70.1 Tg CO2_eq. yr(-1). It was concluded that reducing synthetic N application rate for grain crops in China to a reasonable level of 110-150 kg ha(-1) can greatly reduce the emission of greenhouse gases, especially in the major grain-crop production provinces such as Shandong, Henan, Jiangsu, Hebei, Anhui and Liaoning.
  • Authors:
    • Pan, G.
    • Smith, P.
    • Nayak, D.
    • Zheng, J.
    • Cheng, K.
  • Source: Soil Use and Management
  • Volume: 29
  • Issue: 4
  • Year: 2013
  • Summary: To assess the topsoil carbon sequestration potential (CSP) of China's cropland, two different estimates were made: (i) a biophysical potential (BP) using a saturation limit approach based on soil organic carbon (SOC) accumulation dynamics and a storage restoration approach from the cultivation-induced SOC loss, and (ii) a technically attainable potential (TAP) with a scenario estimation approach using SOC increases under best management practices (BMPs) in agriculture. Thus, the BP is projected to be the gap in recent SOC storage to either the saturation capacity or to the SOC storage of uncultivated soil, while the TAP is the overall increase over the current SOC storage that could be achieved with the extension of BMPs. The recent mean SOC density of China's cropland was estimated to be 36.44t/ha, with a BP estimate of 2.21 Pg C by a saturation approach and 2.95 Pg C by the storage restoration method. An overall TAP of 0.62 Pg C and 0.98 Pg C was predicted for conservation tillage plus straw return and recommended fertilizer applications, respectively. This TAP is comparable to 40-60% of total CO2 emissions from Chinese energy production in 2007. Therefore, carbon sequestration in China's cropland is recommended for enhancing China's mitigation capacity for climate change. However, priority should be given to the vast dry cropland areas of China, as the CSP of China is based predominantly on the dry cropland.