Crop Yield In China Research Articles

Straw Incorporation Strategy on Cereal Crop Yield in China

ABSTRACTStraw incorporation (SI) is considered a valid agricultural measure for ameliorating soil quality and sequestrating soil C. This study aimed to quantitatively summarize the response of cereal yield to SI management. Our results showed that compared with straw removal, SI could significantly enhance cereal yield by 7% over all of China across the 9‐yr period. In all regions, SI in coarse‐textured soils increased yields more than in fine‐textured soils. Straw incorporation resulted in greater yield increases for upland crops compared with rice (Oryza sativa L.) cropping, and for rotary tillage compared with plowing and no tillage. Overall, SI‐induced cereal yield increases were greater in areas with a lack of soil nutrients and soil water. The SI‐induced increases of 1 t ha−1 of soil organic C (SOC) storage could increase cereal yield by 44 kg ha−1. If half or full amounts of cereal straw is returned across all of China's agricultural regions, cereal yields would increase by an average of 2.84 and 5.07 Tg yr−1, respectively, which would contribute to achieving the increasing yield requirements of China.

The effect of conservation tillage on crop yield in China

Traditional agricultural practices have resulted in decreased soil fertility, shortage of water resources and deterioration of agricultural ecological environment, which are seriously affecting grain production. Conservation tillage (CT) research has been developed and applied in China since the 1960s and 1970s, and a series of development policies have been issued by the Chinese government. Recent research and application have shown that CT has positive effects on crop yields in China. According to the data from the Conservation Tillage Research Center (CTRC), Chinese Ministry of Agriculture (MOA), the mean crop yield increase can be at least 4% in double cropping systems in the North China Plain and 6% in single cropping systems in the dryland areas of Northeast and North-west China. Crop yield increase was particularly significant in dryland areas and drought years. The mechanism for the yield increase in CT system can be attributed to enhanced soil water content and improved soil properties. Development strategies have been implemented to accelerate the adoption of CT in China.

Assessing the impact of urban expansion on potential crop yield in China during 1990–2010

Rapid urbanization in China has raised great concerns regarding food security caused by conversion of limited cultivated land to urban use. In this study, the loss of potential crop yield due to urban expansion in China during 1990–2010 was calculated by the Global Agro-Ecological Zones (GAEZ) model. Over this period, potential yield decreased by approximately 34.90 million tons due to urban expansion, accounting for 6.52 % of China’s total actual production. The decrease was 13.07 and 21.83 million tons during the first and second decade, respectively. Key areas of lost potential yield were primarily in the Middle-lower Yangtze Plain and the Huang-Huai-Hai Plain. However, South China became a new key area of lost potential yield during the second decade. These findings provide useful information for the development of land use policy, protection of suitable arable land resources and urban development plans in China.

The impacts of conservation agriculture on crop yield in China depend on specific practices, crops and cropping regions

For smooth and wide application of conservation agriculture (CA), remaining uncertainties about its impacts on crop yield need to be reduced. Based on previous field experiments in China, a meta-analysis was performed to quantify the actual impacts of CA practices (NT: no/reduced-tillage only, CTSR: conventional tillage with straw retention, NTSR: NT with straw retention) on crop yields as compared to conventional tillage without straw retention (CT). Although CA practices increased crop yield by 4.6% on average, there were large variations in their impacts. For each CA practice, CTSR and NTSR significantly increased crop yield by 4.9% and 6.3%, respectively, compared to CT. However, no significant effect was found for NT. Among ecological areas, significant positive effects of CA practices were found in areas with an annual precipitation below 600mm. Similar effects were found in areas with annual mean air temperature above 5°C. For cropping regions, CA increased crop yield by 6.4% and 5.5% compared to CT in Northwest and South China, respectively, whereas no significant effects were found in the North China and Northeast China regions. Among crops, the positive effects of CA practices were significantly higher in maize (7.5%) and rice (4.1%) than in wheat (2.9%). NT likely decreased wheat yield. Our results indicate that there are great differences in the impacts of CA practices on crop yield, owing to regional variation in climate and crop types. CA will most likely increase maize yield but reduce wheat yield. It is strongly recommended to apply CA with crop straw retention in maize cropping areas and seasons with a warm and dry climate pattern.

Spatiotemporal Changes in Crop Residues with Potential for Bioenergy Use in China from 1990 to 2010

China has abundant crop residues (CRE) that could be used for bioenergy. The spatiotemporal characteristics of bioenergy production are crucial for high-efficiency use and appropriate management of bioenergy enterprises. In this study, statistical and remote-sensing data on crop yield in China were used to estimate CRE and to analyze its spatiotemporal changes between 1990 and 2010. In 2010, China’s CRE was estimated to be approximately 133.24 Mt, and it was abundant in North and Northeast China, the middle and lower reaches of the Yangtze River, and South China; CRE was scarce on the Loess and Qinghai–Tibet Plateaus. The quantity of CRE increased clearly over the 20-year analysis period, mainly from an increase in residues produced on dry land. Changes in cultivated land use clearly influenced the changes in CRE. The expansion of cultivated land, which mainly occurred in Northeast and Northwest China, increased CRE by 5.18 Mt. The loss of cultivated land, which occurred primarily in North China and the middle and lower reaches of the Yangtze River, reduced CRE by 3.55 Mt. Additionally, the interconversion of paddy fields and dry land, which occurred mostly in Northeast China, increased CRE by 0.78 Mt. The findings of this article provide important information for policy makers in formulating plans and policies for crop-residue-based bioenergy development in China, and also for commercial ventures in deciding on locations and production schedules for generation of bioenergy.

Effects of long-term repeated mineral and organic fertilizer applications on soil organic carbon and total nitrogen in a semi-arid cropland

To meet and the ever increasing need for food and mitigation of global climate changes, plenty of fertilizers have been used to increase crop yield in China, especially in semi-arid regions. In this study, we investigated the impacts of long-term fertilization on wheat yields, soil organic carbon (SOC) and soil nitrogen (N) in the semi-arid Loess Plateau, China. One fallow and eight winter wheat-wheat (Triticum aestivum L.) rotation cropping plots were selected for the field experiment from 1984 to 2010 in the semi-arid Loess Plateau, China. In total we conducted eight fertilization treatments including no fertilizer, mineral nitrogen fertilizer (N), mineral phosphate (P), cattle manure (M), N+P, N+M, P+M and N+P+M. In 2010, we collected three replicate soil samples from each plot to the depth of 100cm from soil surface. Meanwhile, soil bulk density, SOC, total N, and mineral N (ammonium and nitrate), wheat grain and aboveground biomass yields in each plot were measured. We found that mineral fertilizers, especially those applied together with cattle manure, increased winter wheat grain and aboveground biomass yields dramatically. Moreover, wheat biomass was found to have significant correlation with SOC and soil total N in the 0–20cm soil layer. We also found that SOC and soil N were highest in the topsoil layers (0–30cm) than other layers and declined to the depth of 50cm with insignificant changes from 50 to 100cm in all treatments. Compared to the data in 1984, fertilizer application increased surface soil SOC content, especially for the N+P+M treatment after 26 years cropping and fertilization. However, changes in soil total N and mineral N differed from SOC with decreasing N in mineral-fertilized and fallow plots but increasing N in the M-fertilized plots.

The Possible Effect of Climate Warming on Northern Limits of Cropping System and Crop Yield in China

Significantly increasing temperature since the 1980s in China has become a consensus under the background of global climate change and how climate change affects agriculture or even cropping systems has attracted more and more attention from Chinese government and scientists. In this study, the possible effects of climate warming on the national northern limits of cropping systems, the northern limits of winter wheat and double rice, and the stable-yield northern limits of rainfed winter wheat-summer maize rotation in China from 1981 to 2007 were analyzed. Also, the possible change of crop yield caused by planting limits displacement during the periods 1950s–1981 and 1981–2007 was compared and discussed. The recognized calculation methods of agricultural climatic indices were employed. According to the indices of climatic regionalization for cropping systems, the national northern limits of cropping systems, winter wheat and double rice, and the stable-yield northern limits of rainfed winter wheat-summer maize rotation during two periods, including the 1950s–1980 and 1981–2007, were drawn with ArcGIS software. Compared with the situation during the 1950s–1980, the northern limits of double cropping system during 1981–2007 showed significant spatial displacement in Shaanxi, Shanxi, Hebei, and Liaoning provinces and Beijing municipality, China. The northern limits of triple cropping system showed the maximum spatial displacement in Hunan, Hubei, Anhui, Jiangsu, and Zhejiang provinces, China. Without considering variety change and social economic factors, the per unit area grain yield of main planting patterns would increase about 54–106% if single cropping system was replaced by double cropping system, which turned out to be 27–58% if double cropping system was replaced by triple cropping system. In Liaoning, Hebei, Shanxi, Shaanxi, Gansu, and Qinghai provinces, Inner Mongolia and Ningxia autonomous regions, China, the northern limits of winter wheat during 1981–2007 moved northward and expanded westward in different degrees, compared with those during the 1950s–1980. Taking Hebei Province as an example, the northern limits of winter wheat moved northward, and the per unit area grain yield would averagely increase about 25% in the change region if the spring wheat was replaced by winter wheat. In Zhejiang, Anhui, Hubei, and Hunan provinces, China, the planting northern limits of double rice moved northward, and the per unit area grain yield would increase in different degrees only from the perspective of heat resource. The stable-yield northern limits of rainfed winter wheat-summer maize rotation moved southeastward in most regions, which was caused by the decrease of local precipitation in recent years. During the past 50 yr, climate warming made the national northern limits of cropping systems move northward in different degrees, the northern limits of winter wheat and double rice both moved northward, and the cropping system change would cause the increase of per unit area grain yield in the change region. However, the stable-yield northern limits of rainfed winter wheat-summer maize rotation moved southeastward due to the decrease of precipitation.

The observed relationships between wheat and climate in China

Recent changes in climate have had a measurable impact on crop yield in China. The objective of this study is to investigate how climate variability affects wheat yield in China at different spatial scales. First the response of wheat yield to the climate at the provincial level from 1978 to 1995 for China was analysed. Wheat yield variability was only correlated with climate variability in some regions of China. At the provincial level, the variability of precipitation had a negative impact on wheat yield in parts of southeast China, but the seasonal mean temperature had a negative impact on wheat yield in only a few provinces, where significant variability in precipitation explained about 23–60% of yield variability, and temperature variability accounted for 37–41% of yield variability from 1978 to 1995. The correlation between wheat yield and climate for the whole of China from 1985 to 2000 was investigated at five spatial scales using climate data. The Climate Research Unit (CRU) and National Centers for Environmental Prediction (NCEP) proportions of the grid cells with a significant yield–precipitation correlation declined progressively from 14.6% at 0.5° to 0% at 5° scale. In contrast, the proportion of grid cells significant for the yield–temperature correlation increased progressively from 1.9% at 0.5° scale to 16% at 5° scale. This indicates that the variability of precipitation has a higher association with wheat yield at small scales (0.5°, 2°/2.5°) than at larger scales (4°/5.0°); but wheat yield has a good association with temperature at all levels of aggregation. The precipitation variable at the smaller scales (0.5°, 2°/2.5°) is a dominant factor in determining inter-annual wheat yield variability more so than at the larger scales (4°/5°). We conclude that in the current climate the relationship between wheat yield and each of precipitation and temperature becomes weaker and stronger, respectively, with an increase in spatial scale.

Modeling the Impacts of Soil Organic Carbon Content of Croplands on Crop Yields in China

This study quantified the impacts of soil organic carbon (SOC) content on the grain yield of crops using a biogeochemical model (DNDC, denitrification-decomposition). Data on climate, soil properties, and farming management regimes of cropping systems were collected from six typical agricultural zones (northeast, north, northwest, mid-south, east and southwest regions of China, respectively) and integrated into a GIS database to support the model runs. According to the model, if the initial SOC content in the cropland was increased by 1 g C kg −1, the crop yield may be increased by 176 kg ha −1 for maize in the northeast region, 454 kg ha −1 for a maize-wheat rotation in the north region, 328 kg ha −1 for maize in the northwest region, 185 kg ha −1 for single-rice in the mid-south region, 266 kg ha −1 for double-rice in east region, and 229 kg ha −1 for rice and wheat rotation in southwest region. There is a great potential for enhancing the crop yield by improving the SOC content in each region of China.

Case study of the effects of atmospheric aerosols and regional haze on agriculture: an opportunity to enhance crop yields in China through emission controls?

The effect of atmospheric aerosols and regional haze from air pollution on the yields of rice and winter wheat grown in China is assessed. The assessment is based on estimates of aerosol optical depths over China, the effect of these optical depths on the solar irradiance reaching the earth's surface, and the response of rice and winter wheat grown in Nanjing to the change in solar irradiance. Two sets of aerosol optical depths are presented: one based on a coupled, regional climate/air quality model simulation and the other inferred from solar radiation measurements made over a 12-year period at meteorological stations in China. The model-estimated optical depths are significantly smaller than those derived from observations, perhaps because of errors in one or both sets of optical depths or because the data from the meteorological stations has been affected by local pollution. Radiative transfer calculations using the smaller, model-estimated aerosol optical depths indicate that the so-called "direct effect" of regional haze results in an approximately 5-30% reduction in the solar irradiance reaching some of China's most productive agricultural regions. Crop-response model simulations suggest an approximately 1:1 relationship between a percentage increase (decrease) in total surface solar irradiance and a percentage increase (decrease) in the yields of rice and wheat. Collectively, these calculations suggest that regional haze in China is currently depressing optimal yields of approximately 70% of the crops grown in China by at least 5-30%. Reducing the severity of regional haze in China through air pollution control could potentially result in a significant increase in crop yields and help the nation meet its growing food demands in the coming decades.